Prom.Nr.2013
Optical Investigations
on
Oxycelluloses
Thesis
presented
to
The Swiss Federal Institute of
for the
Technology,
Degree
Zürich
of
Doctor of Technical Science
by
,
\
GORDHANBHAI MATHUR PATEL
from
Bombay (India)
Accepted
on
the recommendation of
Professor Dr. A.
Frey-Wyssling
and Professor Dr. H, Deuel
VERLAG KARL ALBER FREIBURG-MÜNCHEN
1951
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To my Parents
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SUBJECTINDEX
Zusammenfassung
7
Conclusion
8
Introduction
8
12
Part I: Dichroism
12
1. Phenomenon of dichroism
2.
3.
Optics
a)
Direction of
b)
Dichroism
14
ny and na
15
in the streak
oxycelluloses
and that of ramie
dyed
from
an
alcoholic Solution
16
measurement
a) Preparation
b)
13
crystals
15
4. Dichroism of
its
Blue chloride
Blue streak
Methylene
and
Methylene
and habit of
of
Determination of
c) Dyeing
16
oxycelluloses
17
Methylene Blue absorption
of ramie from
an
17
alcoholic Solution
17
d) Method of measuring dichroism
e)
Results and
Part II:
Changes
19
interpretation
refractive
in
indices
and
double
refraction
1. Method
2.
of
Preparation
of
4.
1.
27
rebults
29
Ordinary light
Preparation
2. Examination
of
and electron
in the
Interpretation
microscopical investigations
oxycelluloses
ordinary microscope
3. Examination in the electron
4.
25
oxycelluloses
Interpretation
Part III:
progressive
24
measuring
3. Measurement and
with
24
increase in oxidation of cellulose
microscope
31
31
32
33
33
Discussion
35
Plates
37
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Optical Investigations
on
Oxycelluloses
by Gordhanbhai Mathur Patcl
Aus dem Institut
für Pflanzenphysiologie der Eidgenössischen Technischen
(Vorsteher: Prof. Dr. A. Frey-Wyssling)
Hochschule Zürich
Eingegangen
15. Februar 1951
am
ZUSAMMENFASSUNG:
Es wird
versucht, den Verlauf des oxydativen Celluloseabbaues durch verschiedene
Oxydationsmittel (Periodat, Bichromat, Hypobromit)
zu
differenzieren.
H. Fischer's
valente/100
1.
Söhne
g
Als
drei
(Fig. 5—7).
Cellulose) 1,55
optischen Methoden
von
Ramie
der
Ernst
Firma
verwendet.
der
von
Oxydationsverfahren
Das
mit Hilfe
gebleichte
Dottikon, Schweiz, mit der Methylenblauzahl (= Milliäqui-
A. G.
Der Dichroismus des
allen
wird
Versuchsmaterial
Oxycellulose aufgenommenen Methylenblaus zeigt
zunehmender
mit
lattenförmige Methylenblaumolekül
Oxydation erfolgt
gelagert,
und bei starker
gruppen
(Methylenblauzahlen
von
4
mit
aufwärts)
Oxydation
wird
parallel
steigender
Zahl der
eine zunehmende
gleichen
den
bei
Verlauf
Fasertextur ein¬
zur
gebildeten Karboxyl-
Einlagerung
von
dimeren
Methylenblaumolekülen.
2.
Die
gewählten
micellare
hohen
Änderung
der
Quellung und
Brechungsindex
verschieden
schwächt daher die
der Cellulose in
3.
Im
Brechungsindices
Lichtmikroskop und
dationsverfahren
Periodat-Oxycellulose verquillt
fel
schiedener Breite und
intermicellaren
Länge.
löst sich in feine Fibrillen
von
und zerfällt
Cellulose
und
je nach der
intra-
Hypobromit
scheint
steigender Oxydation
daß mit
in
in Fibrillen und
werden,
es
da der Blendor Mikronbrillen
Substanz,
daß eine
Querstücke
Zerstörung
(Ta¬
ver¬
der
Hypobromit-Oxycellulose
auf, die voneinander getrennt
vermutlich
nicht, Ramiecellulose
von
Die
Oxy¬
Degradationsbilder.
zusammenklebende Mikronbrillen
Quellung
150 oder 200 Ä Durchmesser
zerstört, denn mechanisch gelingt
die nach den drei
verschiedene
ganz
erfolgt (Tafel II).
sind. Hier wird offenbar eine interfibrillare
spalten,
so
Elektronenmikroskop zeigen
Oxycellulosen
Es darf angenommen
parakristallinen
sich
verursacht
optische Anisotropie. Bichromat senkt den
wegzulösen,
zerfällt ohne
I). Bichromat-Oxycellulose
verhält
Periodat
der kristallinen Celluose gemessen werden.
im
hergestellten
Ramiefasern
(Fig. 9—12).
undurchsichtiger Weise,
das Bindemittel der Cellulosemikrofibrillen
schließlich die
der
Doppelbrechung
Oxydationsmethode
in
parakristalline Cellulose,
so
feine Fibrillen aufzu¬
250—400 Ä Durchmesser liefert.
7
G. M. Patel
CONCLUSION:
Dichroism measurement does
1.
In all cases, when
oxycelluloses.
Blue is absorbed in
show any difference between different types of
good
cular chains in the micellar Strands takes
paracrystalline regions. (c) Hypobromite
binding
microscopical
observations
from the x-ray data,
at
reaction and due to intramicellar
permutoid
a
reached, Methylene
of oxidation is
and the electron
measurements
agreement with the conclusion arrived
reaction is
place, (b)
(a)
distortion of mole¬
swelling,
mainly
Chromic acid oxidises
attaeks and dissolves
are
Periodate
the
interfibrillar
the
away
material.
oxycelluloses,
3. In all three types of
occurs
degree
dimeric form.
Refractive indices
2.
in
a
not
sufficient
a
when
a
degree
sufficient
transverse
disintegration
microfibrils
the
of
of oxidation is reached.
INTRODUCTION
According
glucose
is
the
to
accepted
residues combined
chemical Constitution, cellulose is made up of
together
to
form
long
chain molecules. Hence it
obvious that when cellulose is treated with
hydroxyl
into
groups may be attacked and converted into
carboxyl
Each
6-position
nature.
more
is of
residue has three free
hydroxyl
and those in the 2- and
primary
The end
glucose
secondary hydroxyl
An
group.
Certain
can
a
to
attack
also
supposed
attacked very
3-positions
are
one
of
in the
secondary
one
preferentially
may
Further, the glycosidic linkages
giving
rise to smaller molecular
sufficient number of chains is broken, the fibre becomes
be
easily
disintegrated
oxidising agents under
able
oxycellulose1.
groups, the
oxidising agent
may also be oxidised and broken down
chainsla-ih. When
and further
residue of the molecular chain has in addition
attack one of these types of hydroxyl groups.
brittle and
aldehyde
groups. The cellulose thus modified is called
glucose
the
oxidising agent,
an
preferentially
the
into
hydroxyl
that under such
slightly. Following
powder.
controlled conditions such
groups in certain
as
pH,
positions.
conditions, the glycosidic linkages
are
some
few
examples
are
It is
are
of celluloses of
these types.
oxidises
(1) Periodic acid
sitions of the pyranose
further be oxidised
i
8
to
only the hydroxyl
groups in the 2- and
ring and aldehyde groups
carboxyl
groups
by
are
3-po¬
formed2. These
can
the action of chlorous acid3.
Witz, Bull. Soc. Ind. Rouen, 10 (1882) 447; 11 (1883) 2210.
i»
H.
Staudinger
und J.
lb
H.
Staudinger
und J.
Jurisch, Papierfabrikant 35 (1937) 459, 462, 469.
Jurisch, Ber. dtsch. ehem. Ges. 71 (1938) 2283.
2
L. Jackson and C. Hudson, J. Am. Chem. Soc, 59
3
Rutherford, Minor,
Martin and
(1937) 2049;
60
(1938)
989.
Harris, J. Research Natl. Bur. Standard 29 (1942) 131.
Optical lnvestigations
(2) Chromic
acid in the presence of
on
Oxycelluloses
sulphuric acid, gives
product
partly reducing in nature. All the carboxyl groups
are supposed to be in the 6-position of the
pyranose ring4.
the
In
alkaline
(3)
hypobromite oxycellulose, about 40 °/o of the carboxyl
groups are in the 6-position, the remainder probably are in the 2-and
3-positions4.
(4) It has been established that nitrogen dioxide at room temperature
oxidises only the hydroxyl groups in the 6-position into carboxyl groups5.
According to the modern morphological conception of the fine structure
of cellulose, the fibrous cellulose is made up of long molecular chains lying
parallel to the axis of the fibrils. The portion where the chains comb ine to a
chain lattice is called the crystalline region, and where they do not lie
strictly parallel, is called the paracrystalline region. If the molecular chains
are long enough, they
may pass through many crystalline and paracrystal¬
that is
line
rise to
a
acidic and
partly
regions.
on progressive oxidation of cellulose with
the
lines
in the x-ray diagram of cellulose become
interference
acid,
periodic
and
more
more diffuse, indicating that the original crystalline region is
It has been established that
destroyed0.
diagram
On the other
of cellulose,
hand, chromic acid has
suggesting
that it attacks
no
only
effect
the
the x-ray
on
paracrystalline
region7.
Witz8 observed that
oxycellulose
Solutions of their salts, and this
property of oxycelluloses. Due
was
to
recognised by
carboxyl
group
as
COOH +
where R. COOH represents
an
M+
exchange
an
the
represented by
R
him
the introduction of
lose becomes acidic in character and
the
absorb many metals from aqueous
can
^ R
acidic
the characteristic
as
carboxyl
of ions
can
groups, cellu¬
take
place
on
following equation
•
COOM +
H+
oxycellulose and
M
f
is the cation in
oxycellulose can also ab¬
Methylene Blue, from their
the aqueous Solution. Witz further observed that
sorb
cations of basic
organic
dyes
such
as
aqueous Solutions. Since then, this characteristic property has been used
a
qualitative
test
for the detection of
T. P.
5
C. Yackel and W.
ibid 64
(1942)
However,
Kenyon, J.
Am. Chem.
Soc. 64
(1942) 121;
C. Unruh
and W.
127.
6
G. F. Davidson, J. Text. Inst. 32 (1941) T 109.
?
G. F. Davidson, J. Text. Inst. 32 (1941) T 132.
Witz, Bull. Soc. Ind. Rouen 11 (1883) 169.
8
groups in cellulose.
Nevell, J. Text. Inst. 39 (1948) T 118.
*
Kenyon,
carboxyl
as
9
G. M. Patel
employed quantitatively to measure the carboxyl
content of the cellulosic material by Clibbens and Geake9.
The cation of Methylene Blue can be written in one of the following
Methylene Blue
was
first
forms
N
N
II
I
I
CH3
CH3
CH,
I
CH,
IUI!
Cl
Cl
N
CH,
CH3J
It
shown
was
by Clark,
CH3_
LCH3
Para-quinonoid
form
Ortho-quinonoid
N
N
N
Cohen and Gibbs10 that the
form
Methylene
Blue base
the class of strong bases. The chlorine atom is bound electroeither to the sulphur atom (if the ortho structure is correct) or to
belongs
statically
the
N(CHj)2 group (if the para structure is correct).
It is now definitely established that the absorption of Methylene Blue
is essentially a cation exchange reaction according to the following equation
to
=
R
•
COOH +
Mb+
carboxyl
where -COOH represents
^ R
•
COOMb +
H+
groups of cellulose and Mb+ represents
Methylene Blue ions in the aqueous Solution.
Methylene Blue is a lath-shaped molecule, either flat
the
12,5 Ä long and 3,8 A wide11. The molecule
line
joining sulphur
to
may be
or nearly flat, being
slightly bent at the
nitrogen and the
CH3
—
N
groups
are
free
to rotate in any
direction.
CH3
A
comparative study
of the various
(a) Methylene Blue
(d) the alkali
been made, and it has
methods12, such
as
calcium acetate and
absorption, (c)
determining the carboxyl content has
been found that the Methylene Blue absorption method is the best for the
purpose. Hence it might be correct to assume that one -COOH group can
attract only one Methylene Blue molecule. It has been established that long
benzidine dye-stuff molecules lie in the submicroscopic Spaces of cellulose
with their long axes parallel to that of the fibre13. The Methylene Blue moleabsorption, (b)
silver
titration, for
8
10
Shirly Inst. Mem. 19 (1926) 5; or J. Text. Inst. 17 (1926)
Clark, Cohen and Gibbs, U. S. Public Health Reports 40 (1925) 1131.
Clibbens and Geake,
Taylor, Z. Krist.
91
11
W. H.
12
G. F. Davidson and T. P.
13
O.
10
(1935) 450.
Nevell, J. Text.
T 127.
Inst. 39
(1948)
T 102.
Wälchli, Dissertation, Eidgenössische Technische Hochschule, Zürich 1945.
Optical Investigations
od
Oxycelluloses
cule is 12,5 Ä
has
long. In the case of dichromate oxycellulose, a glucose residue
carboxyl group and the Methylene Blue molecule can lie easily
only
along the fibre axis without any hindrance when the ion exchange takes
place. On the other hand, in the case of periodate-chlorite oxycellulose, the
same glucose molecule has two carboxyl
groups in the 2- and 3-positions.
one
When the cation
exchange takes place, two Methylene Blue molecules come
they may sterically hinder one another (depending upon where
positive charge lies) and perhaps be oriented in a different way. An
so near
the
that
attempt has been made
the orientation of
to see
Methylene
whether there exists any such difference in
Blue molecules in both the types of oxy¬
celluloses. For the sake of comparison, hypobromite oxycellulose, where
40 % of the carboxyl groups are supposed to be in the 6-position and the
remainder in the 2- and
how the
investigated
dyed from alcoholic
3-positions, has been examined. Further,
Methylene
Blue molecules
Solution where there is
bination, but where the molecules
Cellulose is
an
are
no
merely
are
.question of chemical
com-
adsorbed.
anisotropic substance and behaves
uniaxial
it has been
oriented in cellulose
in the first
approxima-
optical properties are concerned. The
double
refraction
of
is
phenomenon
mainly due to the crystalline region.
As seen from x-ray diagrams periodic acid is supposed to destroy the cry¬
stalline region, while chromic acid attacks only the paracrystalline region6,7.
tion
as an
crystal
so
far
as
its
The natural conclusion is that, due
to
the
dispersion
of
by periodic acid,
the refractive indices may be affected
than in the
of dichromate
crystalline region
to
a
greater
extent
oxycellulose, since the refractive power is
due
the
to
mainly
crystalline region. The object of the second part of the
present investigation is to see how the refractive indices are affected by
periodic acid and by chromic acid. Again for the sake of comparison, hypo¬
bromite oxycellulose is examined.
The last part describes investigations on periodate-chlorite, dichromate
and hypobromite oxycelluloses with the help of the light and the electron
case
microscope. As will be
later, the three types of oxidants affect cellulose
early stages of oxidation, so far as their refractive indices
concerned. Morphologically there is no differentiation under the light
differently
are
seen
in the
microscope. With increasing degree of oxidation with periodate and
chlorous acid, the fibres swell considerably, and become a jelly-like mass.
hypobromite oxycelluloses, on the other hand, lose
strength and finally fall to powder. It would be interesting to
find out how the breaking of the fibres takes place, and whether the oxi¬
dation is purely a topochemical reaction starting first at few spots as in the
The dichromate and the
their tensile
11
G. M. Patel
case
acetylation14,
of
plane
in the
as
changes
case
whether the oxidation
or
of acid
conclusions
a
certain
Further, from x-ray data and the
hydrolyses)5.
in the refractive indices with
proceeds along
progressive
of oxidation,
increase
the alteration of the fine structure of cellulose have been
on
drawn. An attempt has been made
to see
directly
what
happens
that fine
to
structure, when cellulose is oxidised with different oxidants.
Part I. DICHROISM
1. Phenomenon
of dichroism
Ramie, when dyed from
anisotropic absorption
an
parallel
an
of
alcoholic Solution of
plane polarised Hght.
the vibration-direction of the
to
in the
same
This
the
stages of
Blue shows
plane polarised Hght,
flbres
are
almost colourless. Ramie,
through 90°, they are
oxidation, when dyed with Methylene
intense blue, when turned
in the initial
Methylene
When the fibre axis lies
Blue behaves
way.
phenomenon
is called dichroism and is due to the orientation of
lath-shaped Methylene
Blue molecules in the
submicroscopic
Spaces of
cellulose.
Unlike Substantive
Blue in
a
concentration is
cellulose, the
tative
dye-stuffs (Congo red.Benzopurpurin etc.), Methylene
molecularly dispersed, and when the
dilute aqueous Solution is
it exists
greater,
as
a
dimeric form16. In the
Blue has been
Methylene
absorption
of its carboxyl content;
of
measure
that
means
case
of oxy-
quanti¬
accepted
Methylene Blue
as
a
each
corresponds to one carboxyl group. In that case, Me¬
probably, is absorbed as Single molecules. In the case of
thylene Blue,
ramie dyed from an alcoholic Solution, Methylene Blue is adsorbed in a
non-ionic form, either as single molecules or as very small crystals. At this
stage, however, it cannot definitely be said how the Methylene Blue cations
molecule absorbed
most
are
absorbed
by
the
and the
oxycelluloses
Methylene
Blue molecules
are
explain the
by
orientation of Methylene Blue molecules in the submicroscopic Spaces of
cellulose, the knowledge of the optical behaviour of the Methylene Blue
ramie. In order to
adsorbed
molecules is
Methylene
a
prerequisite. This
Blue
answer
can
this question, and
be derived from the
properties of the
crystals.
14
K. Kanamaru, Helv. Chim. Acta 17
15
A.
Frey-Wyssling, Protoplasma
25
(1934)
1436.
(1936) 261; Papierfabrikant,
ber, 36 (1938) 215.
16
12
to
E. Rabinowitch and F.
Epstein, J.
Am. Chem. Soc. 63
(1941)
69.
International
num-
Optical Invesligations
2.
Optics
and habit
on
Oxycelluloses
of Methylene Blue chloride crystals
Exhaustive work has been carried
out on the optics and habit of Methy¬
crystals by Taylor11. According to him: „Crystals from
dilute hydrochloric acid are elongated plates which when sufficiently thin
are blue by ordinary transmitted light; thick
crystals are opaque and have
brilliant golden green metallic lustre. The crystals usually
grow as sheaf-like
of
each
shows
twin-bonds
parallel aggregates
plates,
plate
nearly parallel to
lene Blue chloride
the direction of
elongation, and even small fragments apparently free from
(on x-ray examination) to be Interpretation twins.
When viewed by plane polarised transmitted light, thin crystals are
bright blue when the vibration-direction is parallel to the elongation (needle
twinning
axis),
and
prove
purple
brown when the vibration-direction is
right angle to
are approximately parallel and
perpendicular to the needle axis, and in convergent light an optic figure is
observed which indicates large axial dispersion, the brushing being red
a
at
the needle axis. The extinction directions
near
a
the centre of the field, blue
on
the other side. The vibration-directions
and ß lie in the
axis, and ß is
gent
light by
plane of the crystal plate, a being parallel to the needle
perpendicular to the plate. The twinning, revealed in conver¬
a
blue band crossing the optic
accurate measurements of
the
figure,
optical properties.
renders
impossible
any
X-ray oscillation photographs and Weissenberg equatorial photographs
indicate that the unit cell is monoclinic with angle ß
97° and with axial
9.5 Ä, b
31.3 Ä and c
6.9 Ä. Hence c-axis is the needle
lengths a
=
=
=
axis and b-axis is normal to the
The
lath-shaped
=
plate
face.
molecules lie with their
lengths approximately parallel
perpendicular to the c-axis."
All this can be represented as shown in Fig. 1. Methylene Blue crystals
have the tendency to develop the (010) plane more than (100) or (001)
plane. Hence most of the crystals lie on this plane. When we examine the
crystals in plane polarised transmitted light, they are blue when the vib¬
ration-direction is parallel to the c-axis and purple brown (or even colourless
in the case of very thin crystals) when the vibration-direction is parallel to
the a-axis. Some crystals incidently lying on the (100) plane are blue when
the vibration-direction is parallel to the c-axis and black (yellow by reflected
to
the b-axis and with their flat faces
through 90°. This direction is that of the b-axis. Since
it coincides with the long axis of the Methylene Blue molecules, the direc¬
tion of maximum absorption of the molecule lies parallel to its long axis.
This conclusion is supported by the optical behaviour of the Methylene
light)
when turned
Blue streak.
13
G. M. Patel
»«
Fig.
Methylene
3.
A
long
simple
1.
Methylene
Blue
BLUE
crystal. (a) Methylene Blue
molerule
Blue streak
way of
determining
the
optical character
of
molecules is the streak. The substance is drawn
a
substance with
mechanically
on
a
glass slide whereby the small particles with their long axis are arranged
parallel to the direction of the streak. This method has been applied by
Frey-Wyssling17 and Weber18 to determine the optical character of plant
and by Neubert19 and Ziegenspeck20 to determine the optical proof
perties
dye-stuffs.
The particles in the streak are submicroscopic, and an ordinary micro¬
scope is unable to reveal any information as regards their orientation. To
examine the streak in the electron microscope, the replica technique was
employed. A grain öf dye was drawn by a metal spatula on a glass slide and
waxes,
the part where it showed the best dichroism
to
make the silica
glass slide,
as
well
17
A.
as
it is difficult to
as
the collodium
in alcohol. Hence
replica
an
as
Methylene
indirect method
Berlin 1938.
"Weber,
Ber. d. Schweiz. Bot. Ges. 52
18
E.
is
H.
Neubert, Kolloidchem. Beih. 20 (1925) 244.
so
H.
Ziegenspeck,
Koll.-Z. 97
(1941)
201.
marked. It is not
remove
Frey-Wyssling, Submikroskopische Morphologie
Derivate,
14
nor
replica
was
(1942)
111.
the
replica
possible
from the
Blue is soluble in ether
was
des
employed.
The streak
Protoplasmas
und
seiner
Optical Invcstigations
was
the
shadowed from die top with silica
Methylene
Blue
on
Oxycelluloses
to
form
insoluble. Then
particles
a
a
layer rendering
replica was made,
very thin
collodium
shadowed with chromium and examined in the electron microscope.
shows that the
submicroscopic Methylene
Blue
particles
are
Fig.
2
oriented in the
direction of the streak.
Fig.
2.
An tliiwon
Direction of
a)
micrograph
of Metlivk^ Ulm
otreak.
Magnification
15 000 X
na in the streak
ny and
Methylene Blue streak shows a strong double
bigger refractive index, n,,, of the streak
is determined with the help of a Gipsum plate Red I21.
A very thin Methylene Blue streak shows the yellow of I order when the
streak lies parallel and the blue of II order when the streak lies perpenThis means that the bigger refractive
dicular to
ny of the Gypsum plate.
Between crossed Nicols the
refraction. The direction of the
index
ny lies perpendicular
na
parallel
b)
Dichroism
to
the direction of the streak
The streak also shows
to
the streak and the smaller refractive index
to
a
(same
as
in the
crystal).
strong dichroism. When the streak lies parallel
plane polarised light, it is colourless; when
the vibration-direction of the
perpendicular,
dichroism
bigger
21
as
it is blue.
Thus
the direction of the
Methylene Blue
strong absorption
streak shows
is the
same as
a
positive
that of the
refractive index ny.
H. Ambronn and A.
Frey,
Das
Polarisationsmikroskop, Leipzig
1926.
15
G. M. Patel
crystal, the direction na is blue, n/3 is purple
compared to the crystal, the streak which has the same
riy
molecular arrangement (Fig. 3) is so thin that na becomes colourless and
ny
blue (n/S also becomes colourless). From this we can conclude that ny lies
parallel to the long axis of Methylene Blue molecules, and the molecules
are blue when the long axis lies parallel to the vibration-direction and
colourless when perpendicular to it.
We have
seen
that in the
is black. As
and
HU
in
,»
Uli III1«
HINDI
(a) Methylene
Blue streak
(b) Methylene
Blue
molecules
*
n«
Fig.
4. Dichroism
The
Methylene
of oxycelluloses and that of
Solution and its
a) Preparation
3. Fine structure of
Blue streak
ramie
dyed from
an
alcoholic
measurement
of
oxycelluloses
oxycelluloses required
were
prepared
ramie from Ernst H. Fischer's Söhne A.
from
commercially bleached
G., Dottikon (Methylene Blue ab-
sorption 1.55). Different degrees of oxidation were obtained by varying the
duration of oxidising treatment. The material-liquor ratio in every case
oxycelluloses were prepared as follows:
(1) Periodate-chlorite oxycelluloses. Ramie was oxidised with 0.01 M
potassium metaperiodate at 20° C. These periodate oxycelluloses were furwas
2 :100. The different types of
ther treated for 18 hours
which
was
at
25° C with acidified sodium chlorite Solution
0.1 M with respect to sodium chlorite and 0.5 M with respect to
phosphoric acid.
(2) Dichromate oxycelluloses.
was
—
0.1 N with respect to
Ramie
sulphuric acid at 20° C.
(3) Hypobromite oxycelluloses.
Solution which
respect
to
was
sodium
oxidised with
was
a
Solution which
potassium dichromate and 0.2 N with respect
0.02 N with
hydroxide.
Ramie
respect
was
to
The Solution
oxidised
at
a
and 0.1 N with
hypobromite
prepared by
was
20° C with
to
the method of
Birtwell, Clibbens, Geake and Ridge22.
22
Birtwell, Clibbens, Geake and Ridge, Shirly Inst. Mem. 8 (1929) 155;
Inst. 21
16
(1930)
T 35.
or
J. Text.
Optical Investigations
The
oxycelluloses
on
Oxycelluloses
then shaken for six hours with 0.1 N
hydrochloric
being renewed after three hours. Finally, they were washed
acid by prolonged washing with distilled water and dried in the
were
acid, the acid
free from
air at
b)
temperature.
room
Determination of
The
of the
Methylene
Blue
absorption
Methylene Blue used was obtained by recrystallisation from
sample for microscopical use from Geigy (Basel). It was then
water
dried
Methylene
recrystalhsed
by the method described by Ferry23.
The Methylene Blue absorption determinations were carried out by the
method of Davidson24. A buffered Solution of the following concentration
in air at
sample
was
room
temperature. The
Blue content of the
determined
was
used for the purpose.
Methylene Blue,
0.2
Veronal,
0.625 m.mole/1
Sodium
hydroxide,
m.mole/1
m.mole/1
0.4
After the
absorption was complete, the oxycelluloses were rinsed with
by hanging in air at room temperature and used for the
dichroism measurements. The absorption of Methylene Blue is expressed
as m.moles of Methylene Blue absorbed by 100
g of oxycellulose.
water, dried
c) Dyeing
of ramie from
an
alcoholic Solution
Methylene Blue is a basic dye and has no affmity for
However, they can absorb Methylene Blue to a certain
alcoholic Solution. Ramie fibres
boiled in alcoholic Solution of
(0.25 %,
0.5
%, 0.75 %)
P'inally, they
extent
first wetted in water in order
are
them swell and then immersed in
cellulosic fibres.
excess
Methylene
of 95% alcohol. Next,
from
to
they
are
Blue of different concentrations
for three hours and allowed to stand for three
rinsed with
an
make
days.
the
adhering Methylene Blue
hung
drying.
Methylene
samples thus
dyed, is determined by the method described by Weber25. The dye is
extracted with 0.01 N hydrochloric acid and estimated photometrically.
and
d)
are
The
in air for
Blue
content of the
Method of measuring dichroism
For the measurement of
dichroic
of
water to remove
eyepiece and
Nicol
two
a
dichroism,
rotatable
simple comparison photometer consisting
a
analyser
were
used26' t3. The dichroic
prisms with their vibration-directions
Ferry, Quart. J.
right angles
23
G.
24
G. F. Davidson,
25
0.
26
J. M. Preston, Modern Textile Mieroscopy, Manchester 1933.
Weber, J.
Pharm. 16
at
Shirly
(1943)
Inst. Mem. 21
Pr. Chem. 158
(1941)
to
eyepiece
one
of
a
consists
another. The
208.
(1947)
47.
33.
17
G. M. Patel
original beam
unpolarised light
of
analyser
another. When the
is
is
brought
polarised
the
in
planes
above them in such
at right angles to one
position that its vibration-
a
parallel to that of one of the two Nicols, one half of the field is completely
dark, while the other half is bright. When the analyser is turned through 45°, the
direction is
in both the fields should be
intensity
by inserting
a
dichroscope,
Nicols in the
Now
equal. But this is not always the case due to the
light partly polarised by the mirror. This effect can be eliminated
polariser at an angle of 45° with the vibration-directions of both the
effect of the
disturbing
the
objeet
in
Next,
line.
the
measure
to
of the
a
field is
above the
brightness
the
intensity
brought
way that its main
analyser
the
the objeet is equal
bright
in such
fields, and arranged
dividing
between the mirror and the objeet.
the
of the
near
the
to
dichroscope
adjacent
line
dividing
to
the
rotated tili the intensity of
is
field. This turning
of the field and hence the
both the
index lies parallel
anisotropic
angle©, gives
intensity of the objeet.
r
Fig.
The extinetion E
of the
light
0
light
4. Derivation of the formula E
can
help
be calculated with the
=
of
log
2
Fig.
4.
Iß
I is the
is the
intensity
intensity of
adjaccnt field, R is the resultant intensity after turning the analyser and
turning angle; then aecording to Malus's law27
R
COS20
Combining
I
I
expressed28
(1)
and
(2)
we
get
turning angle Q
extinetion will be
By putting
both the
cos2©
•
lo
lo
cos2©
I
sin2©"
•
—
0)
=
R^
lo
sin2©
cot2©
(1)
1ORIoJ=l0g]f
=
E
must
—
(90
as
E
From
cos2
:
both
The extinetion E is
18
Suppose
passing through the objeet in the bright field,
after
0
in the
is the
The
cot
=
2
be Iess than
log
(2)
cot 0
45°, otherwise
the
logarithm
and hence the
negative.
the fibres
fields, the
once
extinetion
Weigert, Optische
27
F.
28
Zeiss, Anleitung
zum
parallel
and then
parallel, E||,
and
Methoden der Chemie,
perpendicular
to
the
perpendicular, Ej_,
Leipzig
1927.
Gebrauch des Pulfrich-Photometers.
dividing
can
line of
be measured.
Optical Investigations
The
big
measurements
mean
of 40 fibres.
E||
extinctions
the
are
carried
Leitz monochromator and
along
out
a
Ej_
the
,
the whole ränge of visible spectrum using
Leitz universal
a-Bromo-naphthalene
and
lamp. Every
used
was
absorption
Oxycelluloses
on
as
4
I
=
I0.10"E
mounting medium. From the
a
coefficients Xy
föllowing equation
•
TT
and x_^
can
be obtained from
(J
X
•
a
value thus obtained is the
*
=I„.e
EX
x
=
4
Here, lo
X is the
is the
wave
of the natural
of the
intensity
length
of the
logarithms.
Only
diameter.
a
those
was
d
•
log
beam of
e
light,
(x||—Xj_)
gives
measured with the
lumen and hence the lumeti
fibres
measured
were
I is the
d is the thickness of the
The difference
The thickness of the fibre
Ramie fibre possesses
original
light used,
7t
•
whose
intensity
object
of the
and
object,
is the base
e
the value of dichroism.
help
was
of
micrometer
a
eyepiece.
subtracted from the whole
lumen
distinctly
was
and
seen
measurable.
e) Results
and
interpretation
The results obtained with different types of oxycelluloses and ramie dyed
an alcoholic Solution of different concentrations have been
represented
from
in the
Figs. 5,
Fig.
6 and 7.
5 represents the
fibre
against the
length, reaches a
of oxycelluloses,
absorption coefficient parallel to the axis of the
length. x\\ increases with the increase in the wave
wave
maximum at about 680
m
ju
and then decreases. In the
case
increases almost
along the whole ränge of the visible
xjj
when
the
of
concentration
spectrum
Methylene Blue is raised. In the case
of ramie
by
the
dyed
same
instance,
an
from
an
amount
alcoholic Solution, xy is greater than that produced
Methylene Blue absorbed by oxycelluloses. For
of
absorption
of 2.0 m.moles of
sorption coefficient 0.0069
at 680
m
Methylene
ju; whereas
Blue
to attain
the
absorption coefficient in the case of oxycelluloses,
absorption should be as high as 7 to 9 m.moles.
As
seen
reaches
a
from
Fig. 6,
gives
the
the
same
xj^ also increases with increase in the
celluloses,
Methylene
x_^
along
the whole spectrum with
light
ab¬
value for
Methylene
wave
maximum at about 590 mju and then decreases. In the
increases
a
case
Blue
length,
of oxy¬
the increase of
absorption. In the beginning when the Methylene Blue ab¬
sorption is small, the absorption coefficient x j_ increases faster than xy; as
a result the dichroism becomes smaller and smaller, especially in the
orangeBlue
yellow region
of the spectrum,
giving
rise to
a
minimum
peak.
When
an
Methylene Blue absorption is reached (about
6 m.moles/100 g), x j_ is so big that the dichroism actually becomes negative.
With the increase of Methylene Blue absorption, the maximum peak beOptimum
value
of
19
G. M. Patel
comes
smaller and smaller and
longer
wave
case
coefficient
x
peak being
20
the
same
time it is shifted
towards the
lengths.
Fig.
In the
at
j_
5.
Changes in the absorption coefficient X|| with
increasing absorption of Mcthylene Blue
of ramie
dyed
from
an
also increases with heavier
the
same as
in the
case
of
alcoholic Solution, the
dyeings,
absorption
the region of the maximum
oxycelluloses (Fig. 6).
The
absorption
Optical Investigations
x_l increases to
a
greater
and hence the dichroism
Fig.
than xy in the region of maximum peak,
each other (Fig. 7). Unfortunately, it
extent
in the
absorption
increasing absorption
is not
a
possible
Methylene
to
dye
Oxycelluloses
curves cross
Changes
6.
on
ramie from
Blue content
an
more
of
coefficient
Methylene
x
j_
with
Blue
alcoholic Solution
so
heavily
as to
reach
than 2 m.moles/100 g of cellulose, and
21
G. M. Pate!
hence it is very difficult
with the further
Fig.
7.
to
say whether the dichroism would go
adsorption
Changes
of
Methylene
in dichroism with
Blue
as
in the
increasing absorption
of
loses. However, from the information available, there is
that it should decrease. In the
22
case
of ramie
dyed
on
case
increasing
of
Methylene
no reason
from
oxycellu-
Blue
to
believe
Congo red, the
Optical Investigations
dichroism goes
on
Oxycelluloses
increasing with increasing Congo red content13. The
Congo red molecules are oriented with their long axes parallel to the axis of
on
the fibre in the
dyed
from
absorbed
an
submicroscopic
ions, but
as
aggregates in
Spaces of cellulose. In the
alcoholic Solution of
some
Congo red, should
Blue content.
are
Methylene Blue,
adsorbed and oriented
on
of ramie
increasing with the increasing
as
are
not
molecules
single
as
way oif the other, and the dichroism,
go
case
the molecules
in the
amout of
case
or
of
Methylene
dye-stüff may be oriented as single molecules or as
fprming tiny crystals. If the latter possibility is
the
true,
crystals should normally lie with their long axes parallel to that of
the fibre. We have seen that in a Methylene Blue crystal, the molecules are
oriented with their long axfes perpendicular to that of the crystal. Hence it
follows that the fibre should be blue when the polarised light vibrates per¬
pendicular to the axis of the fibre and colourless when turned through 90°,
The
aggregates of molecules
and this is contrary to the observed fact. The
only alternative possibility is
that Methylene Blue is adjsorbed as single molecules with their long axes
parallel to that of the fibre( The Methylene Blue molecule is nearly flat and
is only 12,5 Ä long and 3,8 Ä wide and can easily be adsorbed at the lattice
surface of cellulose Strands without any steric hindrance29.
Contrary
to
expectation, the dichroism
measurements
on
different types
Methylene Blue
oxycelluloses showed no
molecules, indicating that whether the Methylene Blue molecules attach
themselves to the carboxyl groups in the 6-position or in the 2- and 3-positions of the pyranose ring, the orientation of these molecules seems always
difference in the orientation of
of
to be
the
same.
early stages of oxidation, the dichroism is positive indicating
Methylene Blue molecules are lying with their long axes parallel to
that of the fibre. As the anlount of Methylene Blue absorbed increases after
stronger oxidation, xy increases very little as compared to xj^. That means
some complication due to the increase in the absorption of Methylene Blue
In the very
that the
occurs.
It is shown that the extinction
curves
of aqueous Solutions of
Blue have two maximum bands16. The M-band with
is
more
prominent
maxima is attributed to
of
to monomeric ions
29
A.
Methylene
maximum 656.5 m/t
in dilute Solutions and the D-band with
600 m// is stronger in cohcentrated Solutions. The
Polymerisation
a
a
maximum at
phenomenon
of two
the fact that with increasing concentration, the
Methylene
Blue cations takes
and the D-band is due
Frey-Wyssling, J. Polymer
Sei. 2
(1947)
to
place.
The M-band is due
dimeric ions.
314.
23
G. M. Pate!
It is rather remarkable that the M-band
approximately corresponds to
absorption
oxycelluloses, when the vibration-direction of the plane polarised light is parallel to the axis of the
fibre, and the D-band corresponds to maxima of the absorption coefficient
curves of oxycelluloses, when the vibration-direction is perpendicular to
the fibre axis. If the two corresponding curves of xy and x j_ are combined
together, a resultant curve with two maxima is obtained, which is similar
maxima of the
that of
to
Methylene
prominent with
more
fore,
a
coefficient
Blue Solution. Here too the 600 m/t band becomes
increasing concentration of Methylene Blue. Therehighly oxidised cellulose Methylene Blue is partly
that in
probable
it is
of
curves
absorbed in its dimeric form. This is
no
contradiction to the Statement that
Methylene
Blue molecule is absorbed per one carboxyl group, because
after strong oxidation, pairs of carboxyl groups may occur so close to each
one
other that
may absorb dimeric ions.
they
Part II. CHANGES IN REFRACTIVE INDICES AND
DOUBLE REFRACTION WITH PROGRESSIVE INCREASE
IN OXIDATION OF CELLULOSE
1. Method
of measuring
Ordinarily the refractive index
fibre is immersed in
series of
a
tili
linearly polarised light
a
determined
is
Iiquids
suitable
by
Becke's immersion method.
indices,
of known refractive
is found in which
liquid
Becke line is observed.
no
The fibre is then invisible because the refractive index of the immersion
of the fibre
the
are
polarised light, ny
same.
is
When the fibre lies
measured, when, perpendicular,
But this method is slow and
are
measured
method,
are
by
Iiquids
a
the
tiring,
that of the fibre.
dispersion method
of
Frey-Wyssling
greatcr chromatic
a
series of mixtures of
immersed in the
Iiquids
dispersion
and
liquid
by changing
the
wave
in
length
mixtures. From these values of different
solids.
The
refractive
measured in
hyperbolic
A.
mann,
24
indices
light
and
but when
Frey-Wyssling,
ibid.
the
wave
repeated
lengths
at
is
for the whole
which the fibre
dispersions
dispersions nc—Uq of the Iiquids
a
rule, the dispersion curves
they
397
are
drawn
1/2),
Helv. Chim. Acta 19
22(1939)981.
the
this
in the monochromator
the Abbe-refractometer. As
in nature,
on
to
of
the
liquid
of the refractive index of the fibre is obtained.
(Schleicher and Schuell No.
paper
30
curve
According
this ränge. Next, the fibre
of
becomes invisible, and from the refractive indices and the
mixtures, the dispersion
Iiquids
30. The method is based
than
from Leitz, the outline of the fibre is made invisible. This is
series of
mixture of
a
Here, the refractive indices
with successive increase in the refractive index
refractive index of the fibre lies
liquid
and that
na is measured.
it is very difficult to find
as
liquid
the vibration-direction of the
to
have
prepared. The
to
exactly equal
whose refractive index is
fact that
parallel
The
and examined in
we
on
so-called
obtain
(1936) 900;
dispersion
straight
A.
at
D-line
are
of
Iiquids
are
or
lines. The
Frey-Wyssling
hyperbolic
wave
length
and K. Wuhr-
Optical Investigations
at
which the Becke line
responding dispersion
hence
n^
and
nf—n,-.
is
extinguished
by joining
curve;
of the fibre itself
The whole apparatus used for the
on
Oxycelluloses
liquid mixture,
in each
these points,
we
plotted
is
on
dispersion
get the
the
cor-
and
curve
(Fig. 8).
consisted of
measureinents
(a) A large Leitz Polarisation microscope, Leitz universal larap and
big
a
Leitz
mono-
chromator
(b)
Abbe's refractometer
(c) A glass table through which
(d)
water
could be circulated
A thermostat from which water flowed
at
24°
through
the
glass
table and the refracto¬
meter.
Fig.
8.
Dispersion
curve
with
2.
(thick line joining the circles)
carboxyl
content
of dichromate
oxycellulose
m.moles/100 g
11.77
Preparation of oxycelluloses
The
oxycelluloses used for the
commercially bleached ramie (M.
Where the
with
higher
ratio the
0.1 N
higher degree
Finally,
hydrochloric
of dichromate and
extent
the
was
acid and dried in air
were
at
shaken for six hours with
room
hypobromite oxycelluloses,
were
from the
described before.
required; an oxidising Solution
employed, keeping the material-liquor
oxycelluloses
oxycelluloses
phosphorous pentoxide.
prepared
as
was
that the fibres almost lost their tensile
fibrous form. The
were
absorption 1.55)
of oxidation
initial concentration
same.
measurements
B.
temperature. In the
ramie
was
oxidised
to
case
such
an
but still retained their
strength
preserved carefuUy in
a
desiccator
over
25
G. M. Patel
carboxyl content of oxycelluloses was determined by the Methylene
absorption method as described before and expressed as m.moles of
carboxyl groups per 100 g of oxycellulose.
The choice of the immersion liquid should be carefully made. It should
not penetrate into the intermicellar Spaces of the fibre, otherwise it will give
rise to the Wiener Effect31. Generally, a series of liquid mixtures with successive increase in refractive index is prepared by mixing two liquids having
The
Blue
Table 1. Refractive indices and double refraction of oxycelluloses
A
=
B
=
C
=
Periodale-chlorite
Diehromate
oxycellulose
oxycellulose
Hypobromite oxycellulose
nDx
Cellulose
1.55
1.5969
1.5264
0.0705
A;
Oxycellulose A2
Oxycellulose A3
3.74
1.5964
1.5256
0.0708
8.00
1.5956
1.5252
0.0704
11.49
1.5948
1.5249
0.0699
Oxycellulose A4
Oxycellulose A5
20.00
1.5936
1.6246
0.0690
35.46
1.5922
1.5242
0.0680
Oxycellulose \
Oxycellulose A7
49.49
1.5909
1.5240
0.0669
55.03
1.5894
1.5237
0.0657
1.55
1.5969
1.5264
0.0705
2.9
1.5968
1.5262
0.0706
5.41
1.5962
1.5261
0.0699
B3
7.35
1.5955
1.5262
0.0693
Oxycellulose B4
11.77
1.5948
1.5262
0.0686
1.55
1.5969
1.5264
0.0705
Cellulose
Oxycellulose
B/
Oxycellulose B,
Oxycellulose
Cellulose
Oxycellulose c;
Oxycellulose c2
Oxycellulose C3
Oxycellulose C4
they
4.46
1.5964
1.5270
0.0694
1.5971
1.5275
0,0696
8.89
1.5983
1.5278
0.0705
10.12
1.5991
1.5282
0.0709
are
unsuitable for this pur-
volatility. After a time one liquid evaporates
thereby changing the composition of the mixture and
refraction. Two liquid mixtures mentioned below, which
as
than the other,
hence the index of
penetrate into the intermicellar Spaces of the fibre and which have
constant
refractive index
even
after
long standing,
Hermans32. For lower refractive
Frey-Wyssling
31
A.
32
P. H. Hermans, Contribution
Company,
26
liquids
have different
pose
more
not
—
6.67
different refractive indices. Most of the
by
nfla
nDT
Oxycellulose
do
ni>Y
content
1946.
and H.
Speich,
to
indices,
a
mixture of
Helv. Chim. Acta 25
the
Physics
a
have been recommended
(1942)
butylstearate
and
1474.
of Cellulose Fibres. Elsevier
Publishing
Optical tnvestigations
on
Oxycelluloses
tricresylphosphate and for higher refractive indices, a Solution of diphenylamine in tricresylphosphate to which 1 °/o of hydroquinone was added as an
antioxidant, have been used.
3. Measurement and resulls
The fibres
and then
attained
were
brought
a
immersed in
on
constant
the
glass
a
liquid
mixture for
temperature, the
measurements
all the measurements the temperature
was
The results thus obtained have been
represented
Changes
given
in refractive indices of
with
As
seen
of twelve hours
were
carried
preparation
out.
During
in Table 1 and
graphically
Figs. 9, 10, 11 and 12.
in
9.
period
maintained at about 24° C.
CARBOm CONTCNT
Fig.
a
table. After 15 minutes when the
from
Fig. 9,
progressive
in the
case
(« mol,!/IOO}\
periodate-chlorite oxycellulose
increase in oxidation
of
periodate
chlorite
oxycelluloses
both
decrease with progressive increase in oxidation. In the beginning,
when the degree of oxidation is very small, na decreases to a greater extent
ny and
na
and afterwards ny is affected much
at
first, reaches
In the
case
a
more so
that double refraction increases
maximum and then decreases
of dichromate
(Fig. 12).
oxycellulose (Fig. 10), with increasing degree
remains almost constant. As
of oxidation, ny decreases while
na
double refraction also decreases
(Fig. 12).
a
result the
27
G. M. Patel
1-59(5
C5960
1-5350
f-S?6*
l-5!t]
1-5?«?
1-5!H
1-59*5
I
0
OAKBOKXL
Fig.
10.
Changes
8
«
4
i
10
CONTI NT IM
moltt/lOOq)
in refractive indices of dichromate
with
progressive increase
$2(0
I!
oxycelluloses
in oxidation
(-5? 60
1-53)0
1-5275
t-SSIS
I-59S0
>-5?«5
1-S)?5
t-Sltt
1-5970
0
l
4
Fig.
11.
Changes
CONTCNT
in refractive indices of
with
28
8
6
CARBOX/L
progressive
) 0
I?
(Hm,lri/looi)
hypobromite oxycellulose
increase in oxidation
Optical Invcstigations
On the contrary,
cellulose
degree
as
seen
both n^ and
Fig. 11,
Oxycelluloses
in the
increase with the
of
case
hypobromite
progressive
oxy-
increase in the
beginning, na increases rapidly, and only with
degree of oxidation, ny increases to a greater extent
of oxidation. In the
further increase in the
so
na
from
on
that the double refraction decreases first, reaches
increases
a
minimum and then
again.
00710
1
PCRI0Q4TE-CHU>a|TE
2
DICHROMAIC
OXTCELl.
3
HTP08D0MITI
OXTUlt.
0-0670
0
0660
0
tO
30
!0
Fig.
12.
Changes
CONTCNT
in double refraction of
60
SO
tO
CARBOXn
(M mofej/<ooy)
oxycelluloses
with progressive increase in oxidation
4.
Interpretation
supposed to be made up of long molecular chains
which lie more or less parallel to each other. The region where the chains lie
closely packed and parallel to each other is called crystalline region, and
where they do not lie parallel, paracrystalline region. It has not been possible to decide how long the chains are. The same chain may form the inte¬
gral portion of many crystalline and paracrystalline regions. From x-ray
evidence, it has been calculated that the thickness of the crystalline cellulose
is about 50 to 60 Ä in diameter. These have been designated by Frey-WyssFibrous cellulose is
ling
as
micellar Strands.
From electron
microscopical observations,
lulose is built up of microfibrils with
contain 15 to 20 micellar Strands
a
it has been
diameter of 200—300
(Fig. 13).
the cel¬
proved that
Ä, which would
Further the chain bundles
forming
29
G. M. Patel
and paracrystalline regions are separated by intermicellar
Generally, it is assumed that water and aqueous dilute Solutions can
penetrate only into the intermicellar spaces, and are not able to penetrate
into the crystalline region. This is supported by the fact that cellulose,
though hydrophilic in character, has only a small swelling capacity and can
take up a maximum of 20°/o of its own weight of water. From this, it follows
that a chemical attack by dilute acids and oxidising agents can only occur
at the surface of the crystalline region, and in the paracrystalline region.
the
crystalline
spaces.
showing submicroscopic
Fig.
13.
Cross section
Strands
(m)
and intermicellar spaces
(i). According
spaces
(k),
It is believed that oxidation of cellulose with
reaction. Due to considerable
accessible
to
swelling,
microfibrils
(f),
micellar
Frey-Wyssling, Protoplasma 27,
to
periodate
is
372
permutoid
a
the interior of the fibre is made
the reagent and hence the reaction Starts
not on
the surface,
but from within the micellar Strands. This has been
that
on
progressive oxidation of cellulose with
supported by the fact
periodate, the interference
diagram become more and more diffuse, suggesting that
crystalline region is gradually destroyed6. At the same time the cellulose
becomes more hygroscopic in character. The increase in hygroscopicity is
attributed to the fact that due to the Separation of the cellulose chains of the
original crystalline lattice, more hydroxyl groups are accessible to moisture.
The phenomenon of double refraction is mainly the property of the
crystalline cellulose. In the case of periodate-chlorite oxycellulose, as the
crystalline region is gradually dispersed with the progressive increase in
lines in the x-ray
the
oxidation, the double refraction decreases.
same
due
time, suggesting
to
intramicellar
On the
or
change
able
a
decrease in
density
ny and
of
na
packing
also decrease at the
of the cellulose chains
swelling.
contrary, when cellulose
in dimensions takes
is oxidised with chromic
place.
acid,
no
swelling
This indicates that dichromate is
penetrate into the micellar System,
fact which has been
not
proved by
oxycellulose, the crystalline
region remains intact or little affected, and possibly the paracrystalline
region is attacked, broken down and dispersed. The dispersion may take
to
x-ray examination7. That
30
means
a
in dichromate
Optical Investigations
place
in such
a
way that it aflects
only
on
Oxycelluloses
ny while
na
remains unaltered. It may
possible that a new substance having refractive index equal to na
original cellulose, is produced and the ny we measure is that of the
mixture of the original cellulose and the new substance produced.
Hypobromite oxidation also is accompanied neither by swelling nor any
dimensional changes. With progressive increase in oxidation, fibres loose
their tensile strength as in the case of dichromate oxycellulose. Unfortunately, no Information is available how the x-ray diagram of cellulose is
affected with progressive increase in oxidation. In any case it is not possible
that hypobromite can penetrate into the crystalline region and disperse it,
as there is no swelling. If this were the case, ny and na ought to go down.
On the contrary both the refractive indices increase. Possibly, hypobromite
attacks the crystalline and paracrystalline region in a topochemical fashion.
Only the hydroxyl groups are converted into the carboxyl groups and the
rest of the structure remains intact. The carboxyl groups being optically
more strongly polar, both ny and na increase. An alternative explanation
would be that an amorphous type of cellulose probably acting as a
binding material between the microfibrils is present in cellulose. Hypo¬
also be
of the
bromite attacks and dissolves it
gradually leaving
result both the refractive indices increase and
a
ideal
crystalline
approach
to
those of the
cellulose3S.
The above inferences
of the electron
dently
really happens
together.
the microfibrils alone. As
are
drawn from the observed data, quite
microscopical
will be arrived
Part
observations. The conclusions
at in
the end
by combining
all
indepen-
as
towhat
the facts
III. ORDINABY LIGHT
AND ELECTRON MICROSCOPICAL INVESTIGATIONS
1.
Preparation of oxycelluloses
In part II the
the
physical
The
structure
beyond
Ramie
7
Both
33
was
cut in
was
an
no
changes
in
ordinary microscope.
begin on cellulose
this part of the work,
oxycellulose:
—
oxidised with 0.04 N Solution of
days (Material-liquor
Ramie
are seen
under
that stage.
Periodate-chlorite
(A2)
of the fibres
investigations carried
oxidised
(Aj)
of oridation of cellulose is small, and
degree
oxidised
oxycelluloses
were
as
ratio
potassium periodate for
1:1000).
days.
above for 10
further treated twice for 18 hours with
K. Kanamaru, Helv. Chim. Acta 17
(1934)
a
Solution
1066.
31
G. M. Patel
which
was
0.5 M with respect
phosphoric
acid
Dichromate
(B;)
which
Ramie
acid
was
respect
days
(Material-liquor ratio 1:400).
days with a Solution which
dichromate and 0.8 N with respect
to
Hypobromite oxycellulose:
Ramie
which
temperature with
oxidised for 5
temperature (Material-liquor
(C/)
at room
a
Solution
0.2 N with respect to dichromate and 0.4 N with respect to
was
sulphuric
(B2)
to
—
treated for 4
was
sodium chlorite and 0,5 M with respect
temperature.
at room
oxycellulose:
Ramie
to
was
sulphuric
0.4 N with
acid
at room
:400).
—
oxidised for 2
was
was
ratio 1
to
days
at
0.02 N with respect to
temperature with a Solution
hypobromite and 0,1 with respect
room
hydroxide (Material-liquor ratio 1: 50).
(C2) Hamie was oxidised for 4 days at room temperature with a Solution
which was 0.04 with respect to hypobromite and 0.1 N with respect
to sodium hydroxide (Material-liquor ratio 1:100).
All the oxycelluloses were washed well with distilled water and examined.
to
sodium
ordinary microscope
case
periodate oxidation, fibres swell to a considerable extent
forming a jelly-like mass. When the degree of oxidation is small, they can
still be separated in the dry State. Under the microscope it seems that the
original structure of ramie is lost and the fibres seem to be homogenous and
transparent. When the degree of oxidation is greater, and if the fibres are
allowed to dry, they stick together forming a hard solid mass. So one has
to examine them while they are wet. As seen from Fig. a, Plate I, the fibres
split along the longitudinal direction and ultimately begin to dissolve (Fig. b,
Plate I). With increasing degree of oxidation, the fibres become thinner and
thinner and shrink to a considerable extent, but no breaking in the transverse direction takes place.
In the case of dichromate oxycellulose, in the beginning, rifts appear along
2. Examination in the
In the
of
the transverse direction, and with further
break into pieces
increase
these rifts. The pieces
in oxidation the fibres
be
powdered by
rubbing slightly between the fingers. It seems that the oxidation proceeds
along a particular plane, and breaks the fibres along this plane in a zig-zag
fashion (Fig. e, Plate II). These small pieces further break along transverse
and longitudinal directions.
In die case of hypobromite oxycellulose, rifts are also observable in the
beginning, as in the case of dichromate oxycellulose. They do break along
the transverse direction but at the same time split along the longitudinal
32
along
can
easily
«
Optical Investigations
direction.
Plate III shows
Fig. i,
fragments along
Suspension
Blendor for 2
of
to
of this fine
drop
Oxycelluloses
picture of
a
fibre
Single
breaking
into
both direction s.
3. Examination in the electron
A
a rare
on
oxycellulose
5 minutes,
Suspension
microscope
in distilled water
depending
was
put
stirred in the
was
upon the
Waring
of oxidations. One
degree
the usual collodion-covered
on
grid,
dried, shadowed with chromium and examined in the electron microscope.
In the beginning when the degree of
oxycellulose:
oxidations is small, only a thick homogenous mass is observed. When this
mass is thin enough, we see on the surface the microfibrils closely packed
together (Fig. c, Plate I). With increasing oxidation, the homogenous mass
gradually opens into microfibrils of more or less regulär diameter (Fig. d,
Periodate-chlorite
Plate
I).
—
The thickness of the microfibrils in both
Dichromate
oxycellulose:
fibre breaks up into
long
—
When the
thick pieces and
degree
no
as
well
as
is about 130—140 Ä.
of oxidation is small, the
individual microfibrils
However, with further increase in oxidation,
all dimensions
cases
we see
long
individual microfibrils which
are seen.
thick
are
fragments in
invariably broken
(Fig. f, Plate II). These long thick fragments are further broken up
(Fig. g, Plate II) and the microfibrils are dissolved (Fig. h, Plate II).
On the contrary, in the case of hypobromite
Hypobromite oxycellulose:
oxycellulose, even when the degree of oxidation is very small (the oxycellu¬
lose still having the fibrous form), the whole fibre is opened into individual
up
—
microfibrils of
regulär
thickness of about 150 Ä. With further increase in
degree of oxidation, these fibrils
along the transverse direction (Fig. 1,
the
interesting picture
of
a
are
further
not
Plate III).
solid thick fibril just
Fig.
split,
m,
Üiey
but
break
Plate III shows
being unpacked
into
an
microfibrils,
about 200 Ä thick.
4.
Interpretation
According to the scheraatic representation of the submicroscopic fibre
structure by Frey-Wyssling (Fig. 13), the fibre is made up of microfibrils
which in
turn consist
the microfibrils
of micellar Strands of about 50—60 Ä diameter. That
merely
microfibrils and have
a
touch each other, do not merge into the
diameter of 200—400
Ä, has
neighbouring
been shown
by
Mühle-
Especially in the secondary wall of ramie, the microfibrils are
close together that it is rather difficult to separate them mechanipacked
cally. If the microfibrils merely touch each other, then it is not possible to
have such a compact structure. They must be bound by some interflbrillar
thaler34.
so
84
K. Mühlethaler, Biochimica
et
Biophysica
Acta 3
(1949)
15.
33
G. M. Patel
material, which may be cellulose itself
is out of the
possibility
question,
as
foreign
or some
purified
substance. The latter
ramie is
supposed
to contain
99 <Vo cellulose.
In the
periodate-chlorite oxycellulose, the microfibrils
distinctly as in the case of hypobromite oxycellulose.
of
case
separated
so
are
never
When the
degree of oxidation is greater, the microfibrils are broken, but not separated
distinctly. There is no indication of the dispersion of the intramicrofibrillar
structure, which causes the interference lines of the x-ray diagram of cellu¬
lose
disperse.
Hypobromite
to
seems
and dissolves it away,
increase in
to
attack
leaving
of the microfibrils remains the
the
place along
same,
broken up, but still the thickness
suggesting that further attack of oxi¬
are
transverse
direction. From Fig.
it appears that cellulose is made up of two distinct
splits
into microfibrils
having
which the microfibrils have
by the Observation
on
binding material,
the individual microfibrils-intact. With further
oxidation, the microfibrils
dation takes
the interfibrillar
primarily
a
m,
portions, one which easily
Ä, and the other in
diameter of about 150
diameter of about 200 Ä. This fact is
a
Plate III,
supported
dichromate
oxycellulose.
oxycellulose, the
of dichromate
thick
fragments correspond
hypobromite oxycellulose,
and they are broken down into microfibrils having a diameter of about
200—220 Ä. The thinner fibrils (150 Ä) are from the very beginning attacked
preferentially (Fig. f, Plate II) and are dissolved (Fig. h, Plate II).
The breaking of the microfibrils along the transverse direction can be
explained according to Frey-Wyssling. In a recent publication (in print,
Makromolekulare Chemie), he has attempted to explain the segmentation
of the fibres in the course of hydrolyses. According to him in a microfibril,
the crystalline regions are intercepted by amicroscopic paracrystalline zones
in transverse direction (Fig. 14). The density of packing in the paracrystalIn the
to
case
the thick fibril of
Fig.
üne
zones
sing
are
line
34
the
14.
Fine
Fig.
structure
being less,
an
m,
of
a
Plate III of the
microfibril with
oxidant
can
zones
.question
as
remains undecided.
to
the
transverse zones
easily penetrate and attack them, cauSegments in all different lengths
period of repetition of the paracrystal¬
segmentation of the microfibrils.
found and the
amicroscopic
Optical Investigations
Oxycelluloses
on
DISCUSSION
The dichroism measurements show
rangement of the
Methylene
loses, indicating that
molecules
are
no
difference in the
Blue molecules in different
same
place, yet
the
way.
in the very
even
ar-
types of oxycellu¬
in whatever way the oxidation takes
oriented in the
On the contrary,
practically
early stages
of oxidation, different types
of oxycelluloses show a distinct difference in the refractive indices. As expected from x-ray data, in the case of periodate-chlorite oxycellulose, due to
the dispersion of the crystalline region ny and na and hence the double
refraction go on decreasing with increasing oxidation. This fact is not
directly supported by the electron microscopical examination, as the disper¬
sion of the crystalline regions is not visible. The finest unaltered microfibril
in the case of hypobromite oxycellulose has a diameter of about 150 Ä,
whereas in the case of periodate-chlorite oxycellulose, the diameter is about
130—140 Ä. The difference in diameter may be due to dissolution at the
surface of microfibrils. At the
distortion which
disappear,
to
In the
case
time, there
same
be
must
the interference lines in x-ray
causes
intramicellar
an
diagram
of cellulose
and the refractive indices to decrease.
of dichromate
oxycellulose,
remains constant
na
as
expected
from x-ray data, while ny and the double refraction go on decreasing with
increase in oxidation. The former conclusion that the crystalline region
remains
more or
paracrystalline region is attacked and
affected, is supported by the electron micro¬
the degree of oxidation is small (cellulose still
Iess intact while the
dispersed so that only ny is
scopical investigation. When
having the fibrous form), fibres split
net
up
only
into
long and thick pieces. The
beginning, it attacks only
chemical reaction of dichromate is that, in the
easily accessible to the oxidant. With
crystalline regions are gradually attacked
and broken down into pieces, while the paracrystalline regions are dissolved.
On the contrary, in the case of hypobromite oxycellulose ny and na go
As revealed by the
on increasing with increasing degree of oxidation.
electron microscope, the primary action of hypobromite is to dissolve the
interfibrillar binding material. This binding material being noncrystalline
the
which
paracrystalline regions
are
further increase in oxidation, the
in
character, might have
we measure
a
lower refractive index, and the refractive indices
of the pure cellulose is the
microfibrils and that of the
gradually
As
a
reach
ny
=
dissolved with
binding
mean
material. Since this
refractive
1.6034 and
na
=
indices
of
the
on
ideal
material is
binding
increasing oxidation, the microfibrils
result the refractive indices will go
the
of the refractive indices of the
are
left alone.
they nearly
crystalline cellulose33, viz.
increasing
until
1.5374.
35
G. M. Patel
Finally it may be concluded that ramie cellulose is made up of micro¬
having a diameter varying from 150 to 200 Ä. According to Mühlethaler, the microfibril-thickness varies from 250 to 400 Ä. In his experiment,
fibrils
the fibres
opened
were
into
opened
up
mechanically
individual microfibrils.
and it is
Against
possible that they
the
above
were
not
conclusion,
an
argument may be brought forward that the surface of the microfibrils may
be dissolved away by the oxidant, and as a result the microfibrils become
thinner. But it has been
seen that whatever the degree of oxidation may be,
the thickness of the microfibrils remains almost constant. The further attack
of the
oxidising agent (particularly hypobromite) only
along the transverse direction, and the rest
microfibrils
breaks down the
of the microfibril
remains intact.
The
logy
foregoing
work
was
carried
dance of Frof. Dr. A.
I wish to express my
Frey-Wyssling
the
Laboratory of Plant PhysioTechnology, Zürich, under the gui-
out in
of the Swiss Federal Institute of
for whose advice and encouragement
appreciation and deep gratitude.
Mr. Thakorlal D. Patel without whose financial
would
36
not
have been
possible.
help,
I wish to thank also
the
foregoing
work
Optical Investigations
Oxycelluloses
on
oxycellulose
Plate I. Periodate-chlorit«
(a) Photomicrograph
of
oxycellulose
A,
mojunted
Magnification
(b) Photomicrograph
(c)
of
osycellulose A2 möunted
Magnification 93 X
Electron
micrograph
Magnification
(d)
Electron
oxycellulose
oxycellulose B;
micrograph
Magnification
(g)
Electron
(h)
Plate III.
(i) Photomicrograph
of
Electron
oxycellulose B;
17
oxycellulosc G2
micrograph
Magnification
of
paraffin
oil.
oxycellulose
C.
.^00 X
oxycellulose C,
of
14
micrograph
Magnification
mounted in
630 X
14
(1) Electron micrograph
(m)
X
oxycellulose B,
Ö00 X
of
Hypobromite oxycellulose
Magnification
Electron
B,
X
S00
Magnification
(k)
Ö00
of
micrograph
oil
X
13
micrograph
Magnification
paraffin
mounted in
oxycellulose
of
12
Magnification
Electron
A,
oxycellulose A,
of
Magnification 452
Electron
a-Bromo-naphthalene.
21 f)00 X
Plate II. Dichromate
(f)
in
oxycellulose
of
micrograph
of
a-Bromo-naphthalene.
19 000 X
Magnification
(e) Photomicrograph
in
282 X
^00
of
X
oxycellulose C,
14 000 X
37
G. M. Patel
Plate I
".""
Y
^
»I An
'
1 W\i
«il
I
j/7f
14' "'#ÄV
> u
•''!
'
Ulis 'i'Q'-^
1?)<#^
gas.
•
MVi.\
äfeff/V-^ II wir
»vN
38
>'. fff.
IV.'
'
-
Optical Investigations
on
Oxycelluloses
Plate II
39
G M.Patel
Plate III
40
Curriculum vitae
born
May 23rd, 1920 at Harkundi (Bombay). After having
High School, Godhra, in 1939 I joined Gujarat
College, Ahmedabad, and graduated (B. Sc.) in 1944. In the same year I
joined the Department of Chemical Technology, University of Bombay,
and obtained the degree of B. Sc. Tech, in textile chemistry in 1946. ThereI
was
on
matriculated from the New
after for
a
year and half I worked in the
Corporation, Bombay.
Institute of
I undertook the
Technology in November
laboratory of Ameer Trading
foregoing work at The Swiss Federal
1948 and finished it in November 1950.