polymers
Article
Synthesis of Well-Defined
Poly(N-H Benzamide-co-N-Octyl Benzamide)s and
the Study of their Blends with Nylon 6
Chih-Feng Huang 1, *, Miao-Jia Chen 1 , Ching-Hsuan Lin 1 and Yeo-Wan Chiang 2
1
2
*
Department of Chemical Engineering, National Chung Hsing University, 250 Kuo Kuang Road,
Taichung 402, Taiwan; [email protected] (M.-J.C.); [email protected] (C.-H.L.)
Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology,
National Sun Yat-Sen University, Kaohsiung 804, Taiwan; [email protected]
Correspondence: [email protected]; Tel.: +886-4-2284-0510
Academic Editor: Lloyd M. Robeson
Received: 9 March 2017; Accepted: 10 May 2017; Published: 13 May 2017
Abstract: We synthesized a series of copolybenzamides (PBA) through chain-growth condensation
polymerization (CGCP) of 4-(octylamino)benzoate (M4OB) and methyl 3-(4-(octyloxy)benzylamino)
benzoate (M3OOB) co-monomers. Well-defined copolybenzamides with close to theoretical
molecular weights (Mn ≈ 10,000–13,000) and narrow molecular weight distributions (Mw /Mn < 1.40)
were obtained. Selective removals of the protecting group (i.e., 4-(octyloxy)benzyl group) from
the affording P(M3OOB-co-M4OB) copolybenzamides were subsequently performed to obtain
P(M3NH-co-M4OB) copolymers. These novel N-H-containing copolybenzamides (named as PNHBA)
can not only provide hydrogen bonds for polymer-polymer blends but also have good solubility
in organic solvents. Miscibility of the PNHBA and Nylon 6 blends was investigated by differential
scanning calorimetry (DSC), thermogravimetric analysis (TGA), FT-IR, contact angle analysis,
transmission electron microscope (TEM), and dynamic mechanical analysis (DMA). This study
illustrates a novel type of copolybenzamide with controlled molecular weight and narrow molecular
weight distribution through an effective synthetic strategy, and can be applied to a practical blend of
Nylon 6 with good miscibility.
Keywords: chain-growth condensation polymerization; polybenzamide; Nylon 6; polymer blends
1. Introduction
The development of high-performance polymers has been an important and long-term target of
the past few decades. The study of polymer blends continues to draw attention from both a practical
point of view and in fundamental research for the more precise understanding of the factors dominating
polymer miscibility [1]. Moreover, the simple and effective polymer blending technique has generated
new materials with combinations of the tailored properties that cannot be obtained in individual
polymers. It is, thus, important to study the miscibility and phase behavior of polymer blends.
Most polymer blends are immiscible/incompatible because of the unfavorable enthalpy and entropy
of polymer-polymer mixing. The polymer miscibility can be enhanced through specific interactions,
such as van der Waals forces, dipole-dipole interactions, hydrogen bonding, and electrostatic forces.
The enthalpy and entropy changes associated with different types of hydrogen bonds have been
investigated quantitatively from equilibrium constants using spectroscopy. These studies have
illustrated that the contribution of the hydrogen bond to the free energy of mixing strongly relies on
the amount and type of the hydrogen bonds in the mixture [2]. For example, the good miscibility of
polyamides via hydrogen bonding depends on the balance of the negative contribution of their own
Polymers 2017, 9, 172; doi:10.3390/polym9050172
www.mdpi.com/journal/polymers
Polymers 2017, 9, 172
2 of 13
molecular binding force among the original polyamide chains (i.e., self-association) and the positive
Polymers 2017,
9, 172 interaction with other polymer chains (i.e., inter-association) [3–8].
2 of 13
contribution
of their
Polyamides have been mass-produced for decades. Among them, aliphatic polyamides, such as
association) and the positive contribution of their interaction with other polymer chains (i.e., interpolyamide
6 (Nylon 6) and polyamide 66 (Nylon 66), are the most widely used in daily life. Recently,
association) [3–8].
the high demand
for have
smart/functional
textilesfor
has
drivenAmong
the investigation
of novel
polyamide
blends
Polyamides
been mass-produced
decades.
them, aliphatic
polyamides,
such as
to overcome
the6 drawbacks
ofpolyamide
aliphatic polyamides,
asmost
hydroscopicity
a narrow
processing
polyamide
(Nylon 6) and
66 (Nylon 66),such
are the
widely used and
in daily
life. Recently,
window.
Regarding
their
chemical structures,
of aliphatic
and
polyamides
the high
demand for
smart/functional
textiles hasblends
driven the
investigation
of aromatic
novel polyamide
blends may
to overcome
the drawbacks
of aliphatic
polyamides,
such as hydroscopicity
and a narrow
provide
a facile approach
to enhance
the property
of aliphatic
polyamides. Some
studiesprocessing
have reported
window.
Regarding
their
chemical
structures,
blends
of
aliphatic
and
aromatic
polyamides
may
the presence of inter-association hydrogen bonding between aliphatic and aromatic
polyamides
provide
a facile
approach to enhance the[9–18].
property
aliphatic
polyamides.
Some
resulted
in good
miscibility/compatibility
In of
these
studies,
the entropy
of studies
mixinghave
(∆Sm ) is
reported the presence of inter-association hydrogen bonding between aliphatic and aromatic
basically omitted and, thus, the free energy of mixing (∆Gm ) can be regarded as the enthalpy of
polyamides resulted in good miscibility/compatibility [9–18]. In these studies, the entropy of mixing
the mixing value (∆Hm ) (i.e., ∆Gm ; ∆Hm ) which is represented as kTχψ1 ψ2 , where k = Boltzmann
(ΔSm) is basically omitted and, thus, the free energy of mixing (ΔGm) can be regarded as the enthalpy
constant,
T = absolute temperature, χ = interaction parameter, and ψ = volume fraction of polymer i in
of the mixing value (ΔHm) (i.e., ΔGm ≒ ΔHm) which is represented asi kTχψ1ψ2, where k = Boltzmann
the blending
[19]. temperature,
These reports
the importance
of inter-association
hydrogen
bonding
constant,system
T = absolute
χ =reveal
interaction
parameter, and
ψi = volume fraction
of polymer
i
in aliphatic
and
aromatic
polyamide
blends.
in the blending system [19]. These reports reveal the importance of inter-association hydrogen
Since
2000,
Yokozawa
and coworkers
have been developing chain-growth condensation
bonding
in aliphatic
and aromatic
polyamide blends.
Since 2000,
Yokozawa
and coworkers
haveofbeen
developingpolymers
chain-growth
condensation the
polymerization
(CGCP)
to achieve
the synthesis
condensation
by manipulating
polymerization
(CGCP)
to achieve
the synthesis
of condensation
by manipulating
the
substituent
effects of
monomers
[20–23].
The reactions
differ frompolymers
conventional
polycondensation
substituent
effects
of
monomers
[20–23].
The
reactions
differ
from
conventional
polycondensation
reactions in that the monomers are highly selective in the reaction and react dominantly with the
reactions in that the monomers are highly selective in the reaction and react dominantly with the
polymer
end groups during CGCP, resulting in precise control of the molecular weight (MW ), molecular
polymer end groups during CGCP, resulting in precise control of the molecular weight (MW),
weight distribution (MWD), and functionality. In the preparation of well-defined polybenzamides
molecular weight distribution (MWD), and functionality. In the preparation of well-defined
(PBAs)
through CGCP (Scheme S1, see the Supplementary Material), deprotonation of the monomers
polybenzamides (PBAs) through CGCP (Scheme S1, see the Supplementary Material), deprotonation
usingofa strong
base significantly
deactivates
the ester carbonyl
groupthe
viaester
a resonance/inductive
the monomers
using a strong
base significantly
deactivates
carbonyl group viaeffect
a to
form resonance/inductive
meta-stable intermediate
and, therefore,
the undesired
reaction
among
the monomers
effect compounds
to form meta-stable
intermediate
compounds
and,
therefore,
the
is suppressed.
After adding
with
a reactive ester
reaction
between
undesired reaction
amongan
theinitiator
monomers
is suppressed.
Aftercarbonyl
adding angroup,
initiatorthe
with
a reactive
ester the
carbonyl
group, the reaction
between
the initiator
is highly
favorable
and a new the
initiator
and intermediates
is highly
favorable
and a and
newintermediates
amide linkage
is formed.
Simultaneously,
amide
linkage
is
formed.
Simultaneously,
the
chain-ended
ester
group
is
re-activated
from
the weak
chain-ended ester group is re-activated from the weak electron-donating ability of the newly-formed
electron-donating
ability
of
the
newly-formed
amide
linkage.
Thus,
the
chemical
structures
the
1 groups),
amide linkage. Thus, the chemical structures of the initiators: N-substituents (i.e., the Rof
1 groups), the leaving groups (i.e., the R2 groups), strong bases,
initiators: N-substituents (i.e.,
the
R
the leaving groups (i.e., the R2 groups), strong bases, and the polymerization temperatures can be
and the polymerization temperatures can be altered to efficiently obtain homo-polybenzamides as
altered to efficiently obtain homo-polybenzamides as well as block copolybenzamides [24–27], and
well as block copolybenzamides [24–27], and star-shaped [28–34] and branched polybenzamides [35–
star-shaped
[28–34]for
andpreparing
branchednovel
polybenzamides
However,
preparing novelofwell-defined
38]. However,
well-defined [35–38].
polybenzamides,
theforcopolymerization
mixed
polybenzamides,
of mixed monomers has not been explored to date.
monomers hasthe
notcopolymerization
been explored to date.
In this
synthesized
a series of acopolybenzamides
through CGCP
of 4-(octylamino)benzoate
Instudy,
this we
study,
we synthesized
series of copolybenzamides
through
CGCP of 4(M4OB)
and methyl 3-(4-(octyloxy)benzylamino)benzoate
(M3OOB) co-monomers (Scheme
1). Selective
(octylamino)benzoate
(M4OB) and methyl 3-(4-(octyloxy)benzylamino)benzoate
(M3OOB)
comonomers
(Scheme 1).group
Selective
of the protecting
group
(i.e.,from
4-(octyloxy)benzyl
(OOB)
removal
of the protecting
(i.e.,removal
4-(octyloxy)benzyl
(OOB)
group)
five P(M3OOB-co-M4OB)
group) from five(PBA1–5)
P(M3OOB-co-M4OB)
copolybenzamides
subsequently performed
to
copolybenzamides
was subsequently
performed(PBA1–5)
to obtainwas
P(M3NH-co-M4OB)
copolymers
obtain
P(M3NH-co-M4OB)
copolymers
(PNHBA1–5).
We
can
expect
that
the
PNHBAs
not
only
(PNHBA1–5). We can expect that the PNHBAs not only provide hydrogen bonds but also have good
provide hydrogen bonds but also have good solubility in organic solvents. Blends of PNHBA and
solubility in organic solvents. Blends of PNHBA and Nylon 6 were further investigated by DSC, TGA,
Nylon 6 were further investigated by DSC, TGA, FT-IR, contact angle analysis, TEM, and DMA. Our
FT-IR, contact angle analysis, TEM, and DMA. Our aim was to demonstrate a novel type of polybenzamide
aim was to demonstrate a novel type of polybenzamide obtained using an effective synthetic strategy
obtained
anto
effective
to beusing
applied
Nylon 6synthetic
blends. strategy to be applied to Nylon 6 blends.
Scheme 1. Synthesis of well-defined P(M3OOB-co-M4OB) copolybenzamides through CGCP of
Scheme 1. Synthesis of well-defined P(M3OOB-co-M4OB) copolybenzamides through CGCP of M3OOB
M3OOB and M4OB and selective deprotection of the pendent OOB group.
and M4OB and selective deprotection of the pendent OOB group.
Polymers 2017, 9, 172
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2. Materials and Methods
2.1. Materials
Methyl 4-(tert-butyldimethylsiloxy)benzoate (TBS-MB), methyl 4-(octylamino)benzoate (M4OB)
and methyl 3-(4-(octyloxy)benzylamino)benzoate (M3OOB) were synthesized according to previous
studies [26,27,34]. One mole of lithium hexamethyldisilazide/tetrahydrofuran (1.0 M LiHMDS/THF
solution), 1.0 M tetrabutylammonium fluoride/tetrahydrofuran (1.0 M TBAF/THF solution), LiCl
(99%), NH4 Cl (99.5%), and trifluoroacetic acid (TFA, 98%) were used as received from Sigma–Aldrich
(St. Louis, MO, USA). Nylon 6 (NY6) was obtained from Du Pont (Santa Barbara, CA, USA) (Zytel
211® ; Mn = 41,000 and Mw /Mn = 2.93). All of the solvents were dehydrated prior to use.
2.2. Synthesis of P(M3OOB-co-M4OB) via CGCP
For detailed reaction procedures, the reader is referred to the previous studies [26,27,34]. A general
example of PBA1: A mixture of 1.0 M LiHMDS/THF (5 mL, 5.0 mmol), LiCl (2.1 g, 50 mmol), initiator
TBS-MB (84 mg, 0.25 mmol), M3OOB (3.35 g, 9.0 mmol), M4OB (0.21 g, 1.0 mmol), and 15 mL dry
THF were charged into a 50 mL flask equipped with a three-way cock. The living polycondensations
were conducted under nitrogen at −10 ◦ C. All of the other copolymerizations (abbr.: PBA2–5) with
different ratios of 70/30, 50/50, 30/70, and 10/90 were conducted in the same procedures. After the
reaction finished, the mixture was quenched with saturated NH4 Cl(aq) and extracted with CH2 Cl2 three
times. The collected organic layer was washed with water and dried over MgSO4 . The concentrated
crude was re-dissolved in CH2 Cl2 and reprecipitated into methanol/water = 9/1 (v/v) to afford a
yellowish viscous P(M3OOB-co-M4OB) copolybenzamide (i.e., PBA1: Mn = 12,800, Mw /Mn = 1.24,
yield 85%). The reaction conditions and characteristics of the five polybenzamide copolymers (PBAs)
were summarized in Table 1.
Table 1. Characteristics of the polybenzamide copolymers (PBAs).
Samples
F 1 a (Feeds)
PBA1
PBA2
PBA3
PBA4
PBA5
0.90
0.70
0.50
0.30
0.10
f1
a
(Copolymers)
0.90
0.70
0.48
0.30
0.10
b
M n,GPC
13,330
12,490
11,640
10,790
9940
12,800
10,700
9700
11,300
10,400
M n,th
c
M w /M n
1.24
1.18
1.39
1.29
1.06
P12
d
0.099
0.298
0.498
0.698
0.899
P21
d
0.902
0.704
0.505
0.304
0.102
a
Molar fractions of M3OOB/(M3OOB + M4OB) of feeds (F) and copolymers (f measured by 1 H NMR); b Theoretical
MWs were estimated based on the quantitative monomer consumptions plus MW of the initiator (i.e., Mn,th =
F1 × MW(M3OOB repeating unit) + F2 × MW(M4OB repeating unit) + MWinitiator ); c MWs were estimated by GPC (eluent:
THF) calibrated by polystyrene standards; d Pij : Conditional probabilities of the addition of monomer i to a
growing chain-end with an active j radical. P12 = 1 − P11 = 1/(1 + r1 X) and P21 = 1 − P22 = 1/(1 + r2 X), where
X = [M3OOB]0 /[M4OB]0 [39,40].
2.3. Selective Removal of 4-(octyloxy)benzyl Group (OOB) from PBAs
An example: A 25 mL-flask equipped with a three-way stopcock was dried, purged with nitrogen,
and PBA1 (200 mg) and dry CH2 Cl2 (0.5 mL) were added. TFA (7 mL) was added and the mixture
was stirred at room temperature for three days under nitrogen for the removal of the OOB group.
The concentrated crude product was dissolved in CH2 Cl2 and reprecipitated into hexane three times
to afford PNHBA1 as a yellowish-white powder (72 mg, yield 78%).
2.4. Blend Preparation of PNHBA and NY6
PNHBA1 copolymer and Nylon 6 (NY6) with different weight ratios were dissolved in a co-solvent
containing trifluoroethanol and chloroform (4:1 v/v) [9] with a solution concentration of ca. 3 wt %
solid content. The mixture was precipitated into a non-solvent of methanol with vigorous stirring.
The collected fine powder was washed extensively by methanol, repeatedly, and dried under vacuum
for one day at 50 ◦ C.
Polymers 2017, 9, 172
4 of 13
2.5. Characterization
Gel permeation chromatography (GPC) was equipped with: a Waters 515 pump (Hewlett Packard,
Palo Alto, CA, USA), a Waters 410 differential refractometer (Hewlett Packard, Palo Alto, CA, USA),
and two PSS SDV columns (PSS, Mainz, Germany) (Linear S and 100 Å pore size). The polymers were
tested at 40 ◦ C, using tetrahydrofuran (THF) with a flow rate of 1 mL/min. Polystyrene standards
with different MWs and narrow MWDs were used for calibration. Proton nuclear magnetic resonance
(1 H NMR) analysis of the copolymers was performed using a Bruker 400 MHz system (Bruker, Billerica,
MA, USA). The chemical shift was calibrated by setting the internal standard of deuterated DMSO
at 2.49 ppm or CDCl3 at 7.26 ppm. Fourier transfer infrared (FT-IR) analysis of the blends was
conducted using a Nicolet Avatar 320 FT-IR spectrometer (Nicolet, Madsion, WI, USA) under N2 to
keep sample piece dry and to remove background noise. The polymer was mixed with a KBr pellet
and pressed to form the sample for analysis. The glass transition (Tg ), crystallization (Tc ), and melting
(Tm ) temperatures of the blends were characterized by a Seiko 6220 differential scanning calorimetry
(DSC) (Seiko, Torrance, CA, USA) with a protocol as follows: (1) temperature was increased from
0 to 280 ◦ C, and the sample was left for 30 min to remove thermal history, and then was quenched
by liquid nitrogen; (2) the heat flow from −40 to 280 ◦ C (with a ramp of 20 ◦ C/min) was recorded
under nitrogen. To perform thermogravimetric analysis (TGA) of the blends, a TA Instrument Q50
analyzer (scan rate = 20 ◦ C/min from 30 to 700 ◦ C under nitrogen) with a platinum holder was used.
The Td5% values were determined from the 5% decomposition of the samples. The water contact
angle (CA) of the blends was characterized by the KRÜSS G10 system (KRÜSS, Hamburg, Germany)
under ambient conditions. Solvent casting films were stained by RuO4 and the microstructure images
were detected by a JEOL JEM-2100 transmission electron microscope (TEM) (JEOL, Tokyo, Japan).
For dynamic mechanical analysis (DMA), samples were prepared by solvent casting to a dimension of
0.05 × 10 × 30 mm3 . The analysis was recorded by a PerkinElmer DMA 8000 (PerkinElmer, Waltham,
MA, USA) from 20 to 180 ◦ C (with a ramp of 20 ◦ C/min) under nitrogen in tensile mode.
3. Results and Discussion
Copolymerization of M3OOB and M4OB with different molar feed ratios was firstly carried out
to examine the reactivity between the two monomers. The resulting copolymers were analyzed by
1 H NMR. Figure 1 reveals the main assignments and compositions of P(M3OOB-co-M4OB) based
on the peaks at 4.73 ppm (i.e., peak a from the M3OOB unit) and 3.79 ppm (i.e., peak b from
the M4OB unit), respectively. Based on the ratio of the two peaks (i.e., Ia /Ib ), the copolymerized
fraction of M3OOB (f 1 ) was estimated. The detailed characteristics of the copolymers were analyzed
by GPC and are summarized in Table 1 and Table S1 (see Supplementary Materials). From the
1 H NMR and GPC analysis, a significant relationship between the monomer feeds and copolymer
compositions was observed and well-defined copolybenzamides with MWs close to theoretical values
(Mn ≈ 10,000–13,000) and narrow MWDs (Mw /Mn < 1.40) were shown to be obtained.
Polymers 2017, 9, 172
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Polymers 2017, 9, 172
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Figure 1. 11H NMR spectra (400 MHz, CDCl3) of P(M3OOB-co-M4OB) with different molar feed ratios
Figure 1. H NMR spectra (400 MHz, CDCl3 ) of P(M3OOB-co-M4OB) with different molar feed ratios of
of
M3OOB/M4OB:
(A)
90/10;(B)
(B)70/30;
70/30;(C)
(C)50/50;
50/50; (D)
(D) 30/70;
30/70; and
M3OOB/M4OB:
(A)
90/10;
and (E)
(E) 10/90
10/90((ii)
((ii)values
valueswere
weredetermined
determined
by
the
ratios
of
the
dash-region
of
a
for
characteristics
of
the
M3OOB
unit
and
the
dot-region
by the ratios of the dash-region of a for characteristics of the M3OOB unit and the dot-region of
of bb for
for
characteristics
of
the
M4OB
unit).
characteristics of the M4OB unit).
We further estimated the reactivity ratio of r1(M3OOB) and r2(M4OB) based on the molar ratios between
We further estimated the reactivity ratio of r1(M3OOB) and r2(M4OB) based on the molar ratios
the monomer feeds and copolymers by employing the
Kelen–Tüdos method [8] as follows:
between the monomer feeds and copolymers by employing the Kelen–Tüdos method [8] as follows:
ξ−
where η = G/(α + H) and ξ = H/(α + H)
η = (r1 +
r2
r2
η = (r1 + ) ξ −
where η = G/(α + H ) and η = H/(α + H )
H and G can be estimated
αusing H
α = x2/y and G = x(y − 1)/y, where x = F1/F2 (i.e., the ratio of molar
concentration of monomer 1 and 2 in the feed) 2and y = f1/f2 (i.e., the mole ratio of these monomers in
H and G can be estimated using H = x /y and G = x(y − 1)/y, where x = F1 /F2 (i.e., the
the copolymer). α = √(HmHM) where Hm and HM are the lowest and highest H values
from the
ratio of molar concentration of monomer 1 and 2 in the feed) and y = f 1 /f 2 (i.e., the mole ratio
experiments. Figure 2 displays the Kelen–Tüdos
plot of P(M3OOB-co-M4OB). By interpolating the
√
of these monomers in the copolymer). α = (Hm HM ) where Hm and HM are the lowest and highest
experimental results (η as a function of ξ), we found
r1(M3OOB) = 1.01 and r2(M4OB) = 0.982. The similar
H values from the experiments. Figure 2 displays the Kelen–Tüdos plot of P(M3OOB-co-M4OB).
reactivity ratios indicate the ideal copolymerization behavior of the system. The sequence
By interpolating the experimental results (η as a function of ξ), we found r1(M3OOB) = 1.01 and
distribution of the copolymers was further estimated from the reactivity ratios
based on the
r2(M4OB) = 0.982. The similar reactivity ratios indicate the ideal copolymerization behavior of the system.
statistically conditional probabilities (Pij, as summarized in Table 1) [39,40]. It also illustrated that the
The sequence distribution of the copolymers was further estimated from the reactivity ratios based
copolymerization systems resulted in an ideal random distribution of the monomeric units in the
on the statistically conditional probabilities (P , as summarized in Table 1) [39,40]. It also illustrated
copolymer chain. From results (i.e., Mn ≈ Mn,th, Mij w/Mn < 1.4, F1 ≈ f1, the values of P12 and P21 and thermal
that the copolymerization systems resulted in an ideal random distribution of the monomeric units
properties (discussed later)), it is clear that well-defined copolybenzamides were obtained
in the copolymer chain. From results (i.e., Mn ≈ Mn,th , Mw /Mn < 1.4, F1 ≈ f 1 , the values of P12 and
successfully through the proposed living “chain-growth”
fashion, as shown in Scheme S1 (see
P21 and thermal properties (discussed later)), it is clear that well-defined copolybenzamides were
Supplementary Materials).
obtained successfully through the proposed living “chain-growth” fashion, as shown in Scheme S1
(see Supplementary Materials).
Polymers 2017, 9, 172
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0.8
r1(M3OOB) = 1.01
r2(M4OB) = 0.982
Polymers 2017, 9, 172
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0.4
η
0.8
0.0
r1(M3OOB) = 1.01
r2(M4OB) = 0.982
0.4
-0.4
η
0.0
-0.8-0.4
0.0
0.2
0.4
-0.8
0.0
0.2
0.4
ξ
0.6
0.6
0.8
0.8
1.0
1.0
Figure 2. Kelen-Tüdos plot of M3OOB and M4OB copolymerizations.
Figure 2. Kelen-Tüdos plot of M3OOB
ξ and M4OB copolymerizations.
Removal of the OOB
group
the P(M3OOB-co-M4OB)
copolymers was further
Figure protecting
2. Kelen-Tüdos
plot of in
M3OOB
and M4OB copolymerizations.
Removal of the OOB protecting group in the P(M3OOB-co-M4OB) copolymers was further
conducted to produce the P(M3NH-co-M4OB) copolymers, which possessed not only strong
conducted to produce
theOOB
P(M3NH-co-M4OB)
which possessed
not only strong
hydrogen
the
groupcopolymers,
in
the P(M3OOB-co-M4OB)
copolymers
was further
hydrogenRemoval
bondingof
but
also hadprotecting
good solubility
in polar
solvents. To facilitate
the removal
of the OOB
bonding
but also
had good
solubility
in polar solvents.
Towhich
facilitate
the
removal
of
the OOB
conducted
to
produce
the
P(M3NH-co-M4OB)
copolymers,
possessed
not
only
strong
group, trifluoroacetic acid (TFA) was utilized. Figure 3 shows the 1H NMR
spectra (400 MHz, (A) in
group,
trifluoroacetic
acid
(TFA)
wassolubility
utilized.in polar
Figure
3 shows
the 1 H the
NMR
spectra
hydrogen
bonding but
also
had good
solvents.
To facilitate
removal
of the(400
OOBMHz,
DMSO-d6; (B–E) in CDCl3) after treatment with TFA. Characteristic
peaks in Figure 3a were further
trifluoroacetic
acid
(TFA)
was utilized.
Figure
3 shows
the 1H NMR spectra
(400
(A)3a
inwere
(A) ingroup,
DMSO-d
CDCl
treatment
with
TFA. Characteristic
peaks
inMHz,
Figure
6 ; (B–E) in
3 ) after
assigned to identify
the chemical
structure. The disappearance of the representative signals of the
DMSO-d
6
;
(B–E)
in
CDCl
3
)
after
treatment
with
TFA.
Characteristic
peaks
in
Figure
3a
were
further
further assigned to identify the chemical structure. The disappearance of the representative signals
OOB assigned
group (e.g.,
δ (ppm)the
= 4.25–4.85)
were clearly
observed in the
copolymers
of PNHBA1–
to identify
chemical
structure.
The
of resulting
the in
representative
signals
of the of
of the OOB group
(e.g., δ (ppm)
= 4.25–4.85)
weredisappearance
clearly observed
the resulting
copolymers
5. TheOOB
composition
differences
of
the
PNHBA1–5
samples
are
corresponding
to
the
samples
in Figure
group (e.g., δ (ppm) = 4.25–4.85) were clearly observed in the resulting copolymers of PNHBA1–
PNHBA1–5. The composition differences of the PNHBA1–5 samples are corresponding to the samples
1, respectively.
Furthermore,
the
representative
FT-IR
spectra
before
and
after
treatment
by TFA
5. The composition differences of the PNHBA1–5 samples are corresponding to the samples in Figure
in Figure 1, respectively. Furthermore, the representative FT-IR spectra before and after treatment
1, respectively.
representative
before and
after treatment
by TFA
demonstrated
that Furthermore,
the amine the
group
appearedFT-IR
andspectra
the amide
linkages
remained
(see the
by TFA
demonstrated
the
amine
group
appeared
the
amide
linkages
remained
the
demonstrated
that that
theFigure
amine
group
appeared
and and
the
amide
linkages
remained
(see (see
the
Supplementary
Materials,
S2).
From
these results,
successful
deprotection
and good
solvent
Supplementary
Materials,
Figure
S2).
From
these
results,
successful
deprotection
and
good
solvent
Supplementary
Materials, Figure were
S2). From
these results, successful deprotection and good solvent
solubility
of the copolybenzamides
achieved.
solubility
of the
were
solubility
of copolybenzamides
the copolybenzamides
wereachieved.
achieved.
Figure 3. 1H NMR spectra (400 MHz) of P(M3NH-co-M4OB) copolymers (A: in DMSO-d6, B–E: in
Figure 3. 1 H NMR spectra (400 MHz) of P(M3NH-co-M4OB) copolymers (A: in DMSO-d6 , B–E: in
CDCl3; PNHBA1–5 correspond to the samples in Figure 1, respectively; *: impurities).
CDCl3 ;3.
PNHBA1–5
correspond
the samples
in Figure 1, respectively;
*: impurities).
1H NMR spectra
Figure
(400to
MHz)
of P(M3NH-co-M4OB)
copolymers
(A: in DMSO-d6, B–E: in
CDCl3; PNHBA1–5 correspond to the samples in Figure 1, respectively; *: impurities).
Polymers2017,
2017,9,9,172
172
Polymers
of13
13
77of
In an attempt to investigate the compatibility of the copolymers, we blended the resulting
In an attempt
to investigate
the compatibility
thetraces
copolymers,
we blended
PNHBA1–3
with Nylon
6 (NY6). Figure
4 shows the of
DSC
of the three
blended the
sets resulting
and the
PNHBA1–3
with
Nylon
6
(NY6).
Figure
4
shows
the
DSC
traces
of
the
three
blended
sets
and
the related
related characterization data are summarized in Table 2. Structurally speaking, highly
rigid,
characterization
data
are
summarized
in
Table
2.
Structurally
speaking,
highly
rigid,
symmetrical,
and
symmetrical, and easily packed polymer chains result in high Tg and Tm properties. Furthermore, the
easily
packed
polymer
chains
result
in
high
T
and
T
properties.
Furthermore,
the
more
depressions
g
m
more depressions in the Tg and Tm data, the higher the polymer-polymer miscibility or compatibility.
in the Tg and
Tmobserved
data, thethat
higher
polymer-polymer
miscibility
or compatibility.
it was
However,
it was
the the
melting
behaviors of NY6
and NY6
in the presenceHowever,
of the miscible
observed were
that the
melting
of NY6 and
NY6 in thebetween
presenceTof
the miscible polymers were
polymers
similar.
Webehaviors
further estimated
the variations
c and Tg (i.e., ΔTcg = Tc − Tg) to
similar.
We
further
estimated
the
variations
between
T
and
T
(i.e.,
∆T
=
Tc − T(Figure
the
g
cg blends
g ) to investigate
investigate the homogeneity of the blends [41–43]. In cthe NY6/PNHBA1
4A), a clear
homogeneity
blends [41–43]. In the NY6/PNHBA1 blends (Figure 4A), a clear increase in the T
increase
in theofTthe
g and the Tc was seen but little variation in Tm relative to NY6. With 30 wt% ofg
and
the
T
was
seen
but little
variationwas
in Tacquired,
to NY6.might
With be
30 ascribed
wt% of PNHBA1,
a low Xofc (i.e.,
c
m relative which
PNHBA1, a low Xc (i.e.,
crystallinity)
to suppression
the
crystallinity)
was
acquired,
which
might
be
ascribed
to
suppression
of
the
NY6
chain
mobility
NY6 chain mobility because of the good homogeneity of the blends. In Figure 4B, because
where
of the good homogeneity
of the blends.
In of
Figure
4B, where 14
NY6/PNHBA2
70:30,
a significant
NY6/PNHBA2
= 70:30, a significant
increase
approximately
°C in Tc and a=34
°C difference
in
◦ C in T and a 34 ◦ C difference in ∆T was observed relative to NY6.
increase
of
approximately
14
c
cg
ΔTcg was observed relative to NY6. In the NY6/PNHBA3 blends (Figure 4C), a decrease in Tg was
In the NY6/PNHBA3
blends
(Figure
4C), might
a decrease
in Tg was
but Xcofremained
constant,
observed
but Xc remained
constant,
which
be ascribed
to aobserved
higher content
flexible segments
which
might
be ascribed
to a higher
content
of flexible
(i.e., M4OB
unit)
in PNHBA3.
Thus,
(i.e.,
M4OB
unit)
in PNHBA3.
Thus, the
crystallinity
of segments
NY6 composites
can be
tuned
from ca. 6%
to
the
crystallinity
of
NY6
composites
can
be
tuned
from
ca.
6%
to
17%
by
varying
the
contents
and
17% by varying the contents and compositions of the copolybenzamides. From the results, we can
compositions
of the
copolybenzamides.
From
results, we can
rationally
deduce good
miscibility
rationally
deduce
good
miscibility among
thethe
NY6/PNHBAs
blends.
The thermal
stability
of the
among
the
NY6/PNHBAs
blends.
The
thermal
stability
of
the
homo/copolymers
and
blends
homo/copolymers and blends were then examined using TGA. As shown in Figure S3 were
(see
then examined using
TGA. As simple
shown inand
Figuresmooth
S3 (see Supplementary
simple and
smooth
Supplementary
Materials),
TGA curves Materials),
were observed.
For
the
◦ C because
TGA
curves
were
observed.
For
the
copolybenzamides,
the
char
yields
were
ca.
30%
at
650
copolybenzamides, the char yields were ca. 30% at 650 °C because of the high content of aromatic
of the high
content of aromatic
the ~10%
char yields
to ~10%
withamount
an increase
moiety.
Accordingly,
the charmoiety.
yieldsAccordingly,
increased to
with increased
an increase
in the
of
in the amount of copolybenzamides.
Figure
5 summarizes
Td5%
from the
traces. TIn
all
copolybenzamides.
Figure 5 summarizes
the
Td5% values the
from
the values
TGA traces.
In TGA
all blends,
d5%s
◦ C, which indicates high thermal stability. These results
blends,
T
s
were
in
the
range
of
375–380
d5%
were in the range of 375–380 °C, which indicates high thermal stability. These results imply that
imply that moderately
blending
systems
with good
thermal
stability
were acquired.
moderately
compatible compatible
blending systems
with
good thermal
stability
were
acquired.
(A) NY6/PNHBA1
pure NY6
pure NY6
Heat Flow (Endo
)
pure NY6
(C) NY6/PNHBA3
(B) NY6/PNHBA2
(Ax)90/10
(Bx)90/10
(Cx)90/10
(Ay)80/20
(By)80/20
(Cy)80/20
(Az)70/30
(Bz)70/30
(Cz)70/30
PNHBA1
PNHBA2
PNHBA3
30 100 170 240 30 100 170 240 30 100 170 240
o
Temperature ( C)
Figure
ratios (x
(x== 90/10,
90/10, y:
Figure4.4.DSC
DSCtraces
tracesof
of(A–C)
(A–C)NY6/PNHBA1–3
NY6/PNHBA1–3blends
blendswith
with different
different weight
weight ratios
y: 80/20
80/20
and
z:
70/30).
and z: 70/30).
Polymers 2017, 9, 172
8 of 13
Polymers 2017, 9, 172
8 of 13
410
NY6/PNHBA1
NY6/PNHBA2
NY6/PNHBA3
390
(b)
380
(a)
o
Temperature ( C)
400
Td5% for the blends of
(a)
(b)
(c)
370
(c)
360
100
90
80
NY6 wt%
70
10
0
Figure
s ofs of
NY6/PNHBA1–3
blends
withwith
different
weight
percentages
(a:
Figure 5.5. Summary
Summaryof ofTd5%
Td5%
NY6/PNHBA1–3
blends
different
weight
percentages
NY6/PNHBA1
blends,
b:
NY6/PNHBA2
blends,
and
c:
NY6/PNHBA3
blends).
(a: NY6/PNHBA1 blends, b: NY6/PNHBA2 blends, and c: NY6/PNHBA3 blends).
Table
Table 2.
2. Summary
Summary of
of the
the DSC
DSC results
results of
of NY6/PNHBA1–3
NY6/PNHBA1–3blends.
blends.
Xc (%) b
ΔHm – ΔHc (J/g)
∆H m – ∆H c (J/g)
X c (%) b
pure NY6
44.3
69.7
25.4
220.0
26.1
11.3
pure NY6
44.3
69.7
25.4
220.0
26.1
NY6/PNHBA1
-11.3
NY6/PNHBA1
90/10(Ax)
(Ax)
50.0
76.4
26.5
220.7
22.42
9.7
90/10
50.0
76.4
26.5
220.7
22.42
9.7
80/20(Ay)
(Ay)
49.3
75.2
25.9
221.7
23.14
10.1
80/20
49.3
75.2
25.9
221.7
23.14
10.1
70/30
(Az)
51.8
81.6
29.8
222.6
13.52
5.9
70/30 (Az)
51.8
81.6
29.8
222.6
13.52
5.9
PNHBA1
99.0
PNHBA1
99.0
-NY6/PNHBA2
NY6/PNHBA2
-15.1
90/10 (Bx)
41.9
68.2
26.3
218.2
34.71
90/10(By)
(Bx)
41.9
68.2
26.3
218.2
34.71
15.1
80/20
42.5
70.3
27.8
218.0
20.30
8.8
70/30
50.4
84.4
34.0
218.9
19.25
8.4
80/20(Bz)
(By)
42.5
70.3
27.8
218.0
20.30
8.8
PNHBA2
79.9
-34.0
70/30 (Bz)
50.4
84.4
218.9
19.25
8.4NY6/PNHBA3
PNHBA2
79.9
90/10 (Cx)
40.0
74.0
34.1
213.0
32.40
14.1
NY6/PNHBA3
-16.7
80/20 (Cy)
42.6
71.3
28.7217.4
37.95
90/10(Cz)
(Cx)
40.0
74.0
34.1
213.0
32.40
14.1
70/30
32.2
64.8
32.6
217.0
31.96
13.9
PNHBA3
73.5
-28.7
80/20 (Cy)
42.6
71.3
217.4
37.95
16.770/30a (Cz)
31.96(H: enthalpy). 13.9
∆Tcg = Tc − Tg32.2
; b Degree of 64.8
crystallinity (X32.6
∆Hc )/∆Hm o × 100%
c ) % = (∆Hm – 217.0
PNHBA3
73.5
Samples (No.)
Samples (No.)
Tg (°C)
T g (◦ C)
Tc (°C)
T c (◦ C)
ΔTcg a (°C)
∆T cg a (◦ C)
Tm (°C)
T m (◦ C)
ΔTcg = Tc − Tg; Degree
of crystallinity
c) % = (ΔHm – ΔH
c)/ΔHmwere
× 100%
(H: enthalpy).
The inter-association
interactions
of the (X
NY6/PNHBA1
blends
further
analyzed by FT-IR
◦ C. Figure 6 shows two regions of the FT-IR spectra ((A) 4000–2500 and (B) 1800–1400 cm−1 )
at 100
The inter-association interactions of the NY6/PNHBA1 blends were further analyzed by FT-IR
with
blending
ratios.
a higher
PNHBA1,
broadeningand
of the
and amide
at 100various
°C. Figure
6 shows
twoWith
regions
of thecontent
FT-IR of
spectra
((A) 4000–2500
(B) amine
1800–1400
cm−1)
−1 ) occurred, especially for the amide II peak (variations
I/II
peaks
(i.e.,
at
3300
and
1640/1540
cm
with various blending ratios. With a higher content of PNHBA1, broadening of the amine and amide
of half-height
27,1640/1540
(b) 31, (c)cm
36,−1(d)
36, and (e)
39 cm−1for
). These
results
moderate
I/II
peaks (i.e., width:
at 3300(a)
and
) occurred,
especially
the amide
II indicated
peak (variations
of
◦ C.
intermolecular
hydrogen
bonding
between
NY6
and
PNHBA1
at
100
−1
half-height width: (a) 27, (b) 31, (c) 36, (d) 36, and (e) 39 cm ). These results indicated moderate
a
b
o
intermolecular hydrogen bonding between NY6 and PNHBA1 at 100 °C.
Polymers 2017, 9, 172
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Polymers 2017, 9, 172
9 of 13
NY6/PNHBA1
NH
NY6/PNHBA1
(a)100/0 NH
(a)100/0
(A)
(A)
amide Ι
(B)
amideamide
Ι
ΙΙ (B)
amide(a)100/0
ΙΙ
(a)100/0
(b)90/10
(b)90/10
(b)90/10
(b)90/10
(c)80/20
(c)80/20
(c)80/20
(c)80/20
(d)70/30
(d)70/30
(d)70/30
(d)70/30
(e)10/90
(e)10/90
(e)10/90
(e)10/90
(f)0/100
(f)0/100
(f)0/100
(f)0/100
3750
3750
3250
2750
1750 1650 1550 1450
-1
3250 Wavenumber
2750
1750(cm
1650
) 1550 1450
-1
Wavenumber (cm )
Figure
6. FT-IR
FT-IR spectra
spectra of
of NY6/PNHBA1
NY6/PNHBA1 blends
◦ C in
Figure 6.
blends with
with different
different weight
weight ratios
ratios measured
measured at
at 100
100 °C
in
−11
Figure
6.
FT-IR
spectra
of
NY6/PNHBA1
blends
with
different
weight
ratios
measured
at
100
°C
in
regions
of
(A)
4000–2500
and
(B)
1800–1400
cm
.
−
regions of (A) 4000–2500 and (B) 1800–1400 cm .
regions of (A) 4000–2500 and (B) 1800–1400 cm−1.
As mentioned above, the incorporation of hydrogen bonding unit into the copolybenzamides
As mentioned above, the incorporation of hydrogen bonding unit into the copolybenzamides
As enhanced
mentionedthe
above,
the incorporation
unit into Another
the copolybenzamides
indeed
compatibility
between of
thehydrogen
NY6 andbonding
polybenzamide.
benefit of our
indeed enhanced the compatibility between the NY6 and polybenzamide. Another benefit of our
indeed
enhanced
the compatibility
between
the of
NY6
and
polybenzamide.
Anotherhydrophobicity
benefit of our
designed
copolybenzamides
is that the
presence
alkyl
side
chain should enhance
designed copolybenzamides is that the presence of alkyl side chain should enhance hydrophobicity
designed
copolybenzamides
is that
thenature
presence
of alkyl
side chain should
enhance
hydrophobicity
of the composites
with respect
to the
of high
hydrophilicity
of NY6.
We, thus,
examine the
of the composites with respect to the nature of high hydrophilicity of NY6. We, thus, examine the
of
the composites
the nature
high
hydrophilicity
of NY6. We,
thus, examine
the
contact
angle (CA)with
and respect
surface to
energy
(SE) ofofthe
NY6/PHNBA1
composites.
As shown
in Figure
7,
contact angle (CA) and surface energy (SE) of the NY6/PHNBA1 composites. As shown in Figure 7,
contact
angle (CA)
andNY6
surface
of the are
NY6/PHNBA1
composites.
As
shown
in
Figure
7,
the CAs/SEs
of pure
andenergy
pure (SE)
PNHBA1
ca. 71.7°/41.2
mN/m
and
103.4°/24.0
mN/m,
the CAs/SEs of pure NY6 and pure PNHBA1 are ca. 71.7◦ /41.2 mN/m and 103.4◦ /24.0 mN/m,
the
CAs/SEs of
pure
NY6 and
pureblending
PNHBA1amount
are ca.of71.7°/41.2
and 103.4°/24.0
respectively.
With
increases
of the
PNHBA1mN/m
(i.e., 90/10,
80/20, and mN/m,
70/30),
respectively. With increases of the blending amount of PNHBA1 (i.e., 90/10, 80/20, and 70/30),
respectively.
With
increases
the blending
of PNHBA1
(i.e.,PNHBA1.
90/10, 80/20,
and 70/30),
accordingly, the
CAs
and SEs of
gradually
shiftedamount
toward the
value of pure
This indicated
an
accordingly, the CAs and SEs gradually shifted toward the value of pure PNHBA1. This indicated an
accordingly,
the CAs
and SEs gradually
shifted toward the value of pure PNHBA1. This indicated an
additivity effect
of NY6/PNHBA1
blends.
additivity effect of NY6/PNHBA1 blends.
additivity effect of NY6/PNHBA1 blends.
Figure 7. Surface hydrophilicity and energy of NY6/PNHBA1 blends (ratio of a = 100/0, b = 90/10, c =
Figure
hydrophilicity
80/20, d7.=Surface
70/30, and
e = 0/100). and energy of NY6/PNHBA1 blends (ratio of a = 100/0, b = 90/10, c =
Figure 7. Surface hydrophilicity and energy of NY6/PNHBA1 blends (ratio of a = 100/0, b = 90/10,
80/20, d = 70/30, and e = 0/100).
c = 80/20, d = 70/30, and e = 0/100).
We used TEM to visualize the homogeneity of the NY6/PNHBA1 blends. As shown in Figure 8,
We
TEM toofvisualize
the all
homogeneity
of thewere
NY6/PNHBA1
As enhance
shown inthe
Figure
8,
with theused
exception
pure NY6,
of the samples
stained byblends.
RuO4 to
image
with
the exception
of pure
all ofsamples
the samples
were stained by
RuO4 to
the For
image
contrast.
The pure NY6
and NY6,
PNHBA1
were homogeneous
as shown
in enhance
Figure 8a,e.
the
contrast.
TheFigure
pure NY6
and
PNHBA1
samples
homogeneous
shownto
inthe
Figure
8a,e. parts
For the
blends (i.e.,
8b–d),
deep-gray
areas
were were
observed,
which areas
ascribed
stainable
of
blends (i.e., Figure 8b–d), deep-gray areas were observed, which are ascribed to the stainable parts of
Polymers 2017, 9, 172
10 of 13
We used TEM to visualize the homogeneity of the NY6/PNHBA1 blends. As shown in Figure 8,
with the exception of pure NY6, all of the samples were stained by RuO4 to enhance the image contrast.
The
pure
NY6
and PNHBA1 samples were homogeneous as shown in Figure 8a,e. For the blends
Polymers
2017,
9, 172
10 (i.e.,
of 13
Polymers
9, 172
10 of 13
Figure 2017,
8b–d),
deep-gray areas were observed, which are ascribed to the stainable parts of PNHBA1.
The
deep-gray
in Figure
8c,d
are ascribed
to the
shear force
thepreparing
specimen the
by
PNHBA1.
The stripes
deep-gray
stripes
in Figure
8c,d are
ascribed
to thewhile
shearpreparing
force while
PNHBA1.
The
deep-gray
stripes
in
Figure
8c,d
are
ascribed
to
the
shear
force
while
preparing
the
microtone.
With
an increase
theincrease
blending
of PNHBA1,
deep-gray the
dotsdeep-gray
did not show
specimen by
microtone.
Withinan
in amount
the blending
amountthe
of PNHBA1,
dots
specimen
by
microtone.
With
an
increase
in
the
blending
amount
of
PNHBA1,
the
deep-gray
dots
significant
aggregation.
The
deep-gray
dots
had
an
average
diameter
of
30–50
nm,
which
implies
did not show significant aggregation. The deep-gray dots had an average diameter of 30–50 nm,
did
notimplies
show significant
aggregation.
Theindeep-gray
average
diameter
of DSC
30–50
nm,
the
homogeneous
of PNHBA1
NY6.
Thisdots
supports
the
observations
in observations
the
traces.
which
the dispersion
homogeneous
dispersion
of PNHBA1
in had
NY6.an
This
supports
the
in
which
implies
the
homogeneous
dispersion
of
PNHBA1
in
NY6.
This
supports
the
observations
in
In
we In
examined
property
of theproperty
NY6/PNHBA1
sample (90:10sample
w/w) using
theaddition,
DSC traces.
addition,the
wemechanical
examined the
mechanical
of the NY6/PNHBA1
(90:10
0 ) and
the
DSC
traces.
addition,
wethe
examined
the
mechanical
property
of the
NY6/PNHBA1
sample
(90:10
DMA.
Figure
9In
demonstrates
storagethe
modulus
(E
tan
of
pure
(dash
curves)
the
w/w)
using
DMA.
Figure 9 demonstrates
storage
modulus
(E′)δ and
tan
δNY6
of pure
NY6
(dashand
curves)
◦
w/w)
using
DMA.
Figure
9
demonstrates
the
storage
modulus
(E′)
and
tan
δ
of
pure
NY6
(dash
curves)
NY6/PNHBA1
sample (solid
curves)
the temperature
range between
40 and 180
C. The
and the NY6/PNHBA1
sample
(solidincurves)
in the temperature
range−between
−40 and
180presence
°C. The
0 property
and
the
NY6/PNHBA1
sample
(solid
curves)
in
the
temperature
range
between
−40
and
180
°C.
The
of
PNHBA1
increased
the
E
(i.e.,
curve
a
vs.
b).
In
comparison
to
pure
NY6,
tan
δ
and
Tgδ
presence of PNHBA1 increased the E′ property (i.e., curve a vs. b). In comparison to pure NY6,
tan
◦ C) increased
presence
of
PNHBA1
increased
the
E′
property
(i.e.,
curve
a
vs.
b).
In
comparison
to
pure
NY6,
tan
δ
(~60
with
the
presence
of
PNHBA1
(i.e.,
curve
c
vs.
d).
These
observations
are
consistent
and Tg (~60 °C) increased with the presence of PNHBA1 (i.e., curve c vs. d). These observations are
and
T
g (~60 °C) increased with the presence of PNHBA1 (i.e., curve c vs. d). These observations are
with
previous
results.
consistent
withcharacterization
previous characterization
results.
consistent with previous characterization results.
Figure 8. TEM images of NY6/PNHBA1 blends with different weight ratios (ratio of a = 100/0, b =
Figure 8.
8. TEMimages
imagesofofNY6/PNHBA1
NY6/PNHBA1
blends
with different
weight ratios
(ratio
= 100/0,
Figure
blends
with
weight
(ratio
aof= a100/0,
90/10, c = TEM
80/20, d = 70/30,
and e = 0/100; samples
weredifferent
stained by
RuO4 ratios
excepting
forofpure
NY6). b =
b
=
90/10,
c
=
80/20,
d
=
70/30,
and
e
=
0/100;
samples
were
stained
by
RuO
excepting
for
pure
4
90/10, c = 80/20, d = 70/30, and e = 0/100; samples were stained by RuO4 excepting for pure NY6).NY6).
E'E'(MPa)
(MPa)
103
10
(b)
(b)
(a)
(a)
2
102
10
o
48 C
o
48 C
o
60 C
o
60 C
1
101
10
60
60
100
o
140
100
Temperature
(o C) 140
Temperature ( C)
tan
δδ
tan
(d)
(d)
(c)
(c)
20
20
0.34
0.34
0.31
0.31
0.28
0.28
0.25
0.25
0.22
0.22
0.19
0.19
0.16
0.16
0.13
0.13
0.10
0.10
0.07
0.07
0.04
0.04
180
180
NY6/PNHBA1
NY6/PNHBA1
100/0, E'
(a)
100/0,
(a)
(b)
90/10,E'
E'
(b)
90/10,
(c)
100/0, E'
tanδ
(c)
100/0,
(d)
90/10,tan
tanδδ
(d)
90/10, tanδ
3
Figure 9. (a,b) Storage modulus (E’) and (c,d) tan δ of pure NY6 and NY6/PNHBA1 (9:1 w/w) blends
Figure
9.
Storage
(E’) and
and (c,d)
(c,d) tan
tan δδ of
of pure
pureNY6
NY6and
andNY6/PNHBA1
NY6/PNHBA1 (9:1
(9:1 w/w)
w/w) blends
Figure
9. (a,b)
(a,b)
Storage modulus
modulus (E’)
blends
measured
by DMA.
measured by DMA.
4. Conclusions
4.
4. Conclusions
Conclusions
Using CGCP of M3OOB and M4OB co-monomers, we synthesized copolybenzamides with
Using
CGCP
M3OOB
and
M4OB co-monomers,
co-monomers,
we
synthesized
copolybenzamides
Using
CGCP of
of M3OOB
M4OB
we synthesized
copolybenzamides
with
different
compositions.
A seriesand
of well-defined
copolybenzamides
with close
to theoretical MWswith
(Mn
different
compositions.
A
series
of
well-defined
copolybenzamides
with
close
to
theoretical
MWs
(M
n
different
compositions.
A
series
of
well-defined
copolybenzamides
with
close
to
theoretical
MWs
≈ 10,000–13,000) and narrow MWDs (Mw/Mn < 1.40) were obtained. Using the Kelen-Tüdos method
≈(M
10,000–13,000)
and
narrow
MWDs
(M
w/Mn < 1.40) were obtained. Using the Kelen-Tüdos method
≈ 10,000–13,000)
andreactivity,
narrow MWDs
1.40) were
obtained.
Using
the Kelen-Tüdos
to nestimate
the monomer
similar(M
reactivity
for the
individual
monomers
(r1(M3OOB) =
w /Mn < ratios
to
estimate
the monomer
reactivity,
similar
reactivity
ratioscopolymerization
for the
individual
monomers
(r1(M3OOB)
=
method
estimate
the were
monomer
reactivity,
similar
reactivity
ratios
for thebehavior
individual
monomers
1.01
andto
r2(M4OB)
= 0.982)
acquired,
indicating
an ideal
of the
M3OOB
1.01
and
r2(M4OB)
0.982)
were acquired,
indicating
anFT-IR
ideal showed
copolymerization
behavior
of the
M3OOB
1H
(r
= pair.
1.01=and
r2(M4OB)
= 0.982)
acquired,
indicating
an ideal
copolymerization
behavior
of
and
M4OB
Characterization
by were
NMR
and
that selective
removal
of the
OOB
1(M3OOB)
1H NMR and FT-IR showed that selective removal of the OOB
and
M4OB
pair.
Characterization
by
protecting group in the P(M3OOB-co-M4OB) copolymers was successfully achieved to form
protecting
group incopolymers
the P(M3OOB-co-M4OB)
was
successfullyblends
achieved
to form
P(M3NH-co-M4OB)
(abbr.: PNHBA).copolymers
DSC traces of
NY6/PNHBAs
indicated
that
P(M3NH-co-M4OB)
copolymers
(abbr.:
PNHBA).
DSC
traces
blends
the crystallinity of NY6
composites
could
be altered
from
ca. of
6%NY6/PNHBAs
to 17% by varying
theindicated
contentsthat
and
the
crystallinity
composites could
be alteredgood
frommiscibility
ca. 6% to 17%
by the
varying
the contents
and
compositions
ofof
theNY6
copolybenzamides,
indicating
among
NY6/PNHBAs
blends.
compositions
of the T
copolybenzamides,
indicating good miscibility among the NY6/PNHBAs blends.
From TGA curves,
d5%s of the blends were in the range of 375–380 °C, depicting their high thermal
From TGA curves, Td5%s of the blends were in the range of 375–380 °C, depicting their high thermal
Polymers 2017, 9, 172
11 of 13
the M3OOB and M4OB pair. Characterization by 1 H NMR and FT-IR showed that selective removal
of the OOB protecting group in the P(M3OOB-co-M4OB) copolymers was successfully achieved to
form P(M3NH-co-M4OB) copolymers (abbr.: PNHBA). DSC traces of NY6/PNHBAs blends indicated
that the crystallinity of NY6 composites could be altered from ca. 6% to 17% by varying the contents
and compositions of the copolybenzamides, indicating good miscibility among the NY6/PNHBAs
blends. From TGA curves, Td5% s of the blends were in the range of 375–380 ◦ C, depicting their
high thermal stability. We further performed FT-IR and water CA measurements to analyze the
NY6/PNHBA1 blends, in which moderate inter-association interactions and an additivity effect
was observed. In addition, from TEM and DMA measurements of the NY6/PNHBA1 blends, good
homogeneity and enhancement of E’ and tan δ were seen, respectively. In summary, we demonstrated
an effective strategy to synthesize a novel type of polybenzamide, which not only provides hydrogen
bonding but also shows high solubility in organic solvents and good miscibility with Nylon 6.
Supplementary Materials: The following are available online at www.mdpi.com/2073-4360/9/5/172/s1,
Scheme S1: CGCP mechanism for the synthesis of well-defined polybenzamides, Figure S1: 1 H NMR spectra for
the (A) initiator 4-(((tert-butyldimethyl silyl)oxy)methyl)benzoate; (B) monomer methyl 4-(octylamino)benzoate
(M4OB), and (C) methyl 3-(4-(octyloxy)benzylamino)benzoate (M3OOB), Figure S2: Representative FT-IR spectra
of (a) P(M3OOB-co-M4OB) and (b) the resulting PNHBA after deprotection of the OOB group, Figure S3: TGA
traces and Td5% s of (a–c) NY6/PNHBA1–3 blends with different weight ratios, Table S1. Characteristics of
polybenzamide copolymers (PBAs).
Acknowledgments: We thank the Ministry of Science and Technology (MOST105-2218-E-005-004,
MOST105-2221-E-005-084-MY2 and MOST105-2628-E-005-003-MY3) for financial support.
Author Contributions: Chih-Feng Huang and Miao-Jia Chen conceived and designed the experiments;
Miao-Jia Chen performed the experiments; Chih-Feng Huang and Miao-Jia Chen analyzed the data;
Ching-Hsuan Lin designed and contributed the analysis tools of high-temperature FT-IR and DMA;
Yeo-Wan Chiang contributed the analysis tools of TEM; and Chih-Feng Huang wrote the paper.
Conflicts of Interest: The authors declare no conflict of interest.
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