Glass transition temperature enhancement of PMMA through copolymerization with PMAAM and PTCM mediated by hydrogen bonding

Article abstract of DOI:10.1016/j.polymer.2009.12.039

A series of poly(methyl methacrylate-co-methacrylamide-co-tricyclodecyl methacrylate) (PMMA-co-PMAAM-co-PTCM) copolymers possessing high glass transition temperatures and high transparency are prepared. By incorporating the aliphatic tricyclodecyl methacrylate moiety into the PMMA-co-PMAA main chain results in high glass transition temperature and high transparency of PMMA-based polymeric material. The TCM content affects the fraction of hydrogen bonding in these terpolymers, small content of TCM does not sacrifice the fraction of hydrogen-bonded association in and does not cause T_g decrease. The extent of free amide group plays the major role in dictating moisture absorption of terpolymers. The incorporation of TCM significantly reduces the moisture absorption of terpolymers due to its hydrophobic and bulky tricyclodecyl group. In addition, the TCM plays the role of inert diluent to convert portion of the strong self-associated hydrogen bonded amide groups into inter-associated hydrogen bonding between carbonyl groups of ester units and MAAM.

Full text of DOI:10.1016/j.polymer.2009.12.039

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Polymer 51 (2010) 883–889
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Glass transition temperature enhancement of PMMA through copolymerization
with PMAAM and PTCM mediated by hydrogen bonding
,
,
Chien-Ting Lin a, Shiao-Wei Kuo b 1, Chih-Feng Huang a, Feng-Chih Chang a
*
a Institute of Applied Chemistry, National Chiao Tung University, Hsin Chu 300, Taiwan
b Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-sen University, Kaohsiung 800, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of poly(methyl methacrylate-co-methacrylamide-co-tricyclodecyl methacrylate) (PMMA-co-
PMAAM-co-PTCM) copolymers possessing high glass transition temperatures and high transparency are
prepared. By incorporating the aliphatic tricyclodecyl methacrylate moiety into the PMMA-co-PMAA
main chain results in high glass transition temperature and high transparency of PMMA-based polymeric
material. The TCM content affects the fraction of hydrogen bonding in these terpolymers, small content
of TCM does not sacrifice the fraction of hydrogen-bonded association in and does not cause Tg decrease.
The extent of free amide group plays the major role in dictating moisture absorption of terpolymers. The
incorporation of TCM significantly reduces the moisture absorption of terpolymers due to its hydro-
phobic and bulky tricyclodecyl group. In addition, the TCM plays the role of inert diluent to convert
portion of the strong self-associated hydrogen bonded amide groups into inter-associated hydrogen
bonding between carbonyl groups of ester units and MAAM.
Received 10 August 2009
Received in revised form
17 December 2009
Accepted 29 December 2009
Available online 11 January 2010
Keywords:
PMMA
Hydrogen bonding
High glass transition temperature
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
PMMA-co-PMAAM copolymers, some of the self-associated
hydrogen-bonded amide groups become inter-associated through
Polymers possessing high glass transition temperatures are
attractive for polymer industry because of strong economic rewards
that may arise from their potential applications. For instance, poly
(methyl methacrylate) (PMMA) is a polymeric material possessing
many excellent properties, such as light weight, high light trans-
mittance, chemical resistance, colorlessness, and good insulation.
The glass transition temperature of PMMA is relatively low at ca.
105 ꢀC, which limits its applications in the optical-electronic
industry such as optical glasses, polymer waveguide, and optical
fiber. Different approaches have been assayed to enhance Tg of non-
aromatic polymers while maintain their high transmittance in near
UV region through copolymerization with different cycloaliphatic
monomers. Santos et al. [1] reported that higher content of meth-
acrylated-b-cyclodextrin copolymerized with poly(hydroxyethyl
methacrylate) results in higher Tg due to the increase of crosslinking
density caused by the methacrylated-b-cyclodextrin. In our
previous studies [2–4], we developed a new approach to raise Tg of
PMMA through strong inter-associative hydrogen bonding interactions
bycopolymerization with a strong proton donor methacrylamide. In
hydrogen bonding to carbonyl groups of MMA units, to raised Tg of
PMMA [3]. However, increasing moisture absorption of PMMA-co-
PMAAM copolymers is unavoidable because MAAM is highly
moisture absorptive. To reduce the moisture absorption, we offered
another novel approach through copolymerization of MMA, MAAM,
and styrene [2]. The hydrophobic styrene units play dual roles in the
terpolymer: (1) as inert diluent segment to enhance inter-associa-
tive hydrogen bonding between MMA and MAAM by reducing the
strong self-associative hydrogen bonding of MAAM, and (2) to
reduce the moisture absorption due to its hydrophobic nature.
However, it is well known that the aromatic group of styrene will
cause poor transmittance in near UV region (250–380 nm).
In this study, we choose copolymerization of MMA, meth-
acrylamide (MAAM), and tricyclodecyl methacrylate (TCM) for
these reasons: (1) PMAAM is known to possess extremely high Tg
(z250 ꢀC); (2) Tg of the copolymers are expected to be higher than
the corresponding polymer blends because of compositional
heterogeneities existed in hydrogen-bonded copolymers [5–7]; (3)
the tricyclodecane-based polymers such as tricyclodecyl methac-
rylates and bis (hydroxymethyl) tricyclodecane have been reported
suitable for optical applications and photo-curing industry with
excellent transmittance in near UV region [8,9]; (4) the bulky and
hydrophobic tricyclodecyl group of TCM will raise Tg and reduce the
moisture absorptions of PMMA-co-PMAAM-co-PTCM terpolymers,
* Corresponding author. Tel./fax: þ886 3 5131512.
E-mail addresses: kuosw@faculty.nsysu.edu.tw (S.-W. Kuo), changfc@mail.nctu.
edu.tw (F.-C. Chang).
1
Fax: 886-7-5254099.
0032-3861/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.polymer.2009.12.039

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C.-T. Lin et al. / Polymer 51 (2010) 883–889
similar to the styrene in poly(MMA-co-MAAM-co-Sty); (5) the TCM
units will also play the role as inert diluent segment, similar to the
styrene, but without absorption near UV region; (6) the carbonyl
group of TCM is able to interact with MAAM effectively through
inter-associative hydrogen bonding as MMA to raise Tg.
over a period of 0.5 h while maintaining the temperature of the
reaction mixture at 0–4 ꢀC and the reaction mixture was stirred for
24 h at room temperature. After removing the formed solid
quaternary ammonium salt, the solution was transferred to
a separating funnel, washed thoroughly with 5 wt% sodium
hydroxide solution, dilute hydrochloric acid, and water, and then
dried over anhydrous magnesium sulfate. On evaporation of the
solvent, oily tricyclodecyl methacrylate was obtained. It was puri-
fied by distillation under vacuum: b.p. ¼ 139–140 ꢀC/3 torr (296 ꢀC/
760 torr [11(b)]). 1H NMR (CDCl3, ppm): 0.8–2.4 (17H, tricyclo-
decyl), 1.92 (3H, methyl), 5.51 and 6.06 (2H, C]CH2).
A
series of random poly(methyl methacrylate-co-meth-
acrylamide-co-tricyclodecyl methacrylate) (PMMA-co-PMAAM-co-
PTCM) copolymers (Scheme 1) were prepared by free radical
polymerization and then characterized by using DSC and FTIR. The
incorporation of the bulky aliphatic TCM group is expected to
maintain good transmittance near UV region of PMMA, while the
hydrogen bonding interaction is able to tie up the bulk group
inhibiting its free rotation and thus raises the copolymer Tg.
2.2.3. Synthesis of poly(methyl methacrylate-co-methacrylamide-
co-tricyclodecyl methacrylate) copolymers
The solution copolymerization of methyl methacrylate, meth-
acrylamide and tricyclodecyl methacrylate was carried out in 1,4-
dioxane at 80 ꢀC under a nitrogen atmosphere in a glass reaction
flask equipped with a condenser. AIBN (1 wt% based on monomers)
was employed as the initiator. The mixture was stirred for ca. 24 h
before being poured into excess isopropyl alcohol vigorous agita-
tion to precipitate the product. The crude copolymer product was
purified by redissolving it in 1,4-dioxane and then adding this
solution dropwisely into a large excess of isopropyl alcohol. This
procedure was repeated several times and then the residual solvent
of the final product was removed under vacuum at 70 ꢀC for 1 day
to yield pure white poly(methyl methacrylate-co-methacrylamide-
co-tricyclodecyl methacrylate). The chemical composition of the
copolymer was determined by the use of elemental analysis and 1H
NMR spectroscopy.
2. Experimental
2.1. Materials
Methyl methacrylate was purchased from Aldrich chemical
company that was purified by distillation under nitrogen before
polymerization. Theradicalinitiatorazobisisobutyronitrile(AIBN)was
recrystallized from ethyl alcohol prior to use.1,4-dioxane was distilled
under vacuum and then used as the solvent for the copolymerization
experiments performed in solution. Tricyclo [5.2.1.02,6]-decan-8-one
(tricycle-decan-8-one) was purchased from TCI chemical company.
Methacryloyl chloride, sodium borohydride and tricycle-decan-8-one
were used as received without further purification.
2.2. Synthesis
2.3. Characterizations
2.2.1. Synthesis of tricyclodecyl alcohol (reduction of tricyclodecyl
ketone) [10]
The elementary analyses (EA) of N, C, and H atoms in the
polymers were determined by an auto elementary analysis equip-
ment using helium as the carrier gas. The glass transition temper-
ature of the copolymer was determined using a Du-Pont DSC-9000
DSC system. The sample was kept at 200 ꢀC for 1 min and then
cooled quickly to 30 ꢀC from the melt of the first scan. The value of
Tg was obtained as the inflection point of the jump heat capacity at
a scan rate of 20 ꢀC/min within the temperature range of 30–250 ꢀC.
All measurements were conducted under a nitrogen atmosphere.
Molecular weights and molecular weight distributions were
determined by gel permeation chromatography (GPC) using
a Waters 510 HPLC-equipped with a 410 Differential Refractometer
and three Ultrastyragel columns (100, 500, and 103 Å) connected in
series using THF as eluent at a flow rate of 0.4 mL/min. The
molecular weight calibration curve was obtained using polystyrene
standard. Infrared spectra of the copolymer films were determined
by using the conventional NaCl disk method. The 1,4-dioxane
solution containing the blend was cast onto a NaCl disk. The film
used in this study was thin enough to obey the Beer–Lambert law.
FTIR measurements were performed on a Nicolet Avatar 320 FTIR
spectrophotometer; 32 scans were collected at a spectral resolution
of 1 cmꢁ1 1H NMR spectra of these copolymers were recorded on
a Brucker ARX300 spectrometer using CDCl3 as the solvent.
Tricyclo [5.2.1.02,6]-decan-8-one (0.01 mol) and 50 mL ethanol
were placed in a 100-mL round-bottom flask equipped with
a magnetic stirrer. After stirring the reaction mixture for 5 min at
room temperature, sodium borohydride (NaBH4, 0.05 mol) was
added and the reaction mixture was stirred for 15 h at room
temperature. After adding H2O (50 mL) and ether (100 mL), the
solution was transferred to a separating funnel, washed thoroughly
with 5 wt% sodium hydroxide solution, dilute hydrochloric acid,
and water, and then dried over anhydrous magnesium sulfate. On
evaporation of the solvent, oil tricyclodecyl alcohol was obtained.
1H NMR (CDCl3, ppm): 0.6–2.6 (17H, tricyclodecyl), 3.7 and 4.2 (1H,
endo and exo).
2.2.2. Synthesis of tricyclodecyl methacrylate [11(a)]
Tricyclodecyl alcohol (0.05 mol), 4-dimethylamino pyridine
(DMAP, 0.05 mol) and 50 mL dried THF were fed in a 250-mL round-
bottom flask equipped with a magnetic stirrer, dropping funnel and
thermometer. The reaction mixture was cooled to 0–4 ꢀC using an
ice and salt mixture. Then, 0.06 mol of methacryloyl chloride in
dried THF (20 mL) was added dropwisely to the reaction mixture
CH3
C
CH3
C
CH3
C
H2
C
H2
C
H2
C
*
*
y
z
x
3. Results and discussion
C
O
C
O
O
3.1. Copolymer analyses
OCH3
NH2
O
Table 1 lists all monomer feed ratios, copolymer compositions,
molecular weights and glass transition temperatures of poly(MMA-
co-MAAM-co-TCM) terpolymers. For convenience, we use mono-
mer feeds to define the specimen codes. For example, 90-8-2 means
90 mol% of MMA, 8 mol% of MAAM and 2 mol% of TCM in poly-
Scheme 1. Chemical structure of PMMA-co-PMAAM-co-PTCM.

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C.-T. Lin et al. / Polymer 51 (2010) 883–889
885
Table 1
these terpolymers show a single glass transition temperature,
indicating that these terpolymers are mostly in short blocks and
homogeneous in the range 10–30 nm [4]. Therefore, the incorpo-
ration of MAAM and TCM monomers into PMMA main chain can be
considered as random. In poly(MMA-co-MAAM-co-Sty) terpoly-
mers, the styrene units play a role as an inert diluent segment on
the PMAAM polymer chain to reduce the strength of MAAM self-
associative hydrogen bonding [4]. Unlike styrene, the TCM unit is
able to interact with MAAM effectively through inter-associative
hydrogen bonding as MMA to raise Tg, and the hydrogen-bonded
rigid tricyclodecyl group of TCM also can raise Tg.
In Fig. 1(a) and (b), at constant 90 and 85 mol% of MMA, the
increase of TCM content results in Tg decrease, implying that
hydrogen bonding interaction between MMA and MAAM is the
main reason of high Tg of the copolymer. In Fig. 1(c) at a constant
80 mol% of MMA, the Tg of the composition of 80-16-4 is slightly
higher than that of 80-20-0. Moreover, in Fig. 1(d) and (e) at
constant 70 and 60 mol% of MMA, the Tgs of the compositions of
70-24-6 and 60-32-8 are comparable to those of 60-40-0 and 70-
30-0, indicating that small amount of TCM replacing for MAAM
does not cause Tg reduction of the terpolymer. Small amount TCM
replacing MAAM with decreasing proton donor for this hydrogen
bonding in terpolymer system does not cause Tg decrease of the
terpolymer because of the rigid and tied tricyclodecyl group of
TCM. However, excess replacement of TCM for MAAM results in Tg
decrease due to lower content of proton donor in the terpolymer
system.
Poly(MMA-co-MAAM-co-TCM) terpolymers synthesized in this study.
Polymer Monomer feed (mol%) Polymer composition (mol%) Mw
Tg(ꢀC)
(g/mol.)
MMA MAAM TCM MMA
MAAM
TCM
100-0-0 100
0
10
8
0
0
2
100
92.6
0
7.4
4.1
4.7
5.2
4.8
11.1
11.6
9.1
4.3
3.0
13.8
11.4
9.1
9.5
6.5
19.7
16.1
9.7
0
0
57,000 105
29,500 114
34,700 118
34,000 109
90-10-0
90-8-2a
90-6-4
90-4-6
90-2-8
85-15-0
85-12-3
85-9-6
90
90
90
90
90
85
85
85
85
85
80
80
80
80
80
70
70
95.3
94.0
92.0
91.5
88.9
88.3
87.8
90.3
89.1
86.2
88.3
88.1
81.3
81.8
80.3
81.4
82.6
81.3
79.1
72.4
72.1
75.4
75.2
66.2
0.6
1.3
2.8
3.7
0
0.1
3.1
5.4
7.9
0
0.3
2.8
9.2
11.7
0
2.5
7.7
12.4
14.4
0
6
4
4
6
38,400
29,300
96
97
2
8
15
12
9
0
3
6
23,600 120
25,900 119
31,700 115
26,400 118
85-6-9
6
9
85-3-12
80-20-0
80-16-4
80-12-8
80-8-12
80-4-16
70-30-0
70-24-6
70-18-12 70
70-12-18 70
70-6-24
60-40-0
60-32-8
3
12
0
4
25,100
84
20
16
12
8
35,600 133
34,300 142
26,600 117
22,800 101
30,200 103
28,300 140
32,200 138
29,800 130
20,800 114
28,100 110
29,500 170
34,600 163
23,800 147
29,900 130
20,700 132
8
12
16
0
4
30
24
18
12
6
40
32
24
16
8
6
12
18
24
0
6.3
6.5
70
60
60
27.6
26.7
20.2
11.5
6.3
8
1.2
4.4
13.3
27.5
60-24-16 60
60-16-24 60
60-8-32
16
24
32
60
a
90-8-2 is defined by the monomer feed, which means 90 mol% of MMA, 8 mol%
of MAAM and 2 mol% of TCM content in poly(MMA-co-MAAM-co-TCM) terpoymers.
The other samples are also defined in the same way.
3.3. FTIR analyses
(MMA-co-MAAM-co-TCM) terpolymers. The reactivity ratios (r) of
(MMA þ MAAM) and TCM in the terpolymers were estimated by
graphical method of Kelen–Tudos method [12]:
Fourier transform infrared spectroscopy is one of the most
powerful tools for identifying and investigating hydrogen bonding
in polymers. Fig. 2 displays FTIR spectra recorded at room
temperature for pure PMAAM, PMMA and PTCM. Pure PMAAM
exhibits two bands at 1650 and 1600 cmꢁ1 corresponding to the
amide I (C]O stretching vibrations) and amide II (N–H bending
vibrations) bands. The carbonyl stretching bands of pure PMMA
r2ð1 ꢁ
3
Þ
q
¼ r13
ꢁ
(1)
g
where 1 stands for (MMA þ MAAM) and 2 for TCM.
q, 3, and g
are
mathematical functions of G and F are defined in Table 2. On plotting
versus , a linear plot was obtained. The intercepts at ¼ 1
¼ 0 and
gave –r2/ and r1, respectively. The values obtained for r1 and r2 were
and pure PTCM are nearly overlapped at 1730 cmꢁ1 and 1729 cmꢁ1
,
q
3
3
3
corresponding to their respective free carbonyl groups. In our
previous study [3], the absorption of the amide I group of the
MAAM shifts to higher wavenumber and its intensity decreases
upon increasing the MMA content in the PMMA-co-PMAAM
copolymers, implying that fraction of the self-associated hydrogen-
bonded amide groups convert into inter-association through
hydrogen bonding to carbonyl groups of MMA units. Fig. 3 displays
FTIR spectra recorded at room temperature for these terpolymers.
Similar phenomenon was also observed by incorporating the PS
units in the poly(MMA-co-MAAM-co-Sty) copolymers [4]. Unlike
polystyrene, the carbonyl group of TCM can also interact with NH2
group of MAAM through hydrogen bonding, and its absorption
peaks of the free and hydrogen-bonded carbonyl stretching are
essentially same as to those for the carbonyl group of MMA, split-
ting into two bands at 1730 and 1718 cmꢁ1. Therefore, the carbonyl
stretching bands located between 1620 and 1800 cmꢁ1 are split
into four major absorptions, 1660, 1680, 1718, and 1730 cmꢁ1, cor-
responding to hydrogen-bonded carbonyl stretching of amide I,
free carbonyl stretching of amide I, hydrogen-bonded carbonyl
stretching of ester, and free carbonyl stretching of ester, respec-
tively. These four peaks can be fitted well to the Gaussian function.
Values of aHB/aF ¼ 1.5 for MMA and 1.2 for MAAM are employed
[13], and Table 3 summaries the results from curve fitting of these
spectra in terms of the fraction of free and hydrogen-bonded
carbonyl of amide (MAAM) and ester (MMA and TCM). At constant
90 and 85 mol% of MMA, the increase of TCM content results in Tg
decrease mainly due to reduce of the available proton donor MAAM
g
r1 ¼ 3.08 and r2 ¼ 3.42. The same methodology can be employed to
determine the reactivity ratios of (MMA þ TCM) and MAAM, and the
value r1 for (MMA þ TCM) and r2 for MAAM are 1.29 and 0.19,
respectively. The reactivity ratio of the copolymer has been calcu-
lated previously (PMMA-co-PMAAM: rPMMA ¼ 1.38, rPMAAM ¼ 0.24)
[4]. As a result, the reactivities of these monomers in poly(MMA-co-
MAAM-co-TCM)
copolymer
system
follow
the
order
MMA > MAAM > TCM. Furthermore, the molecular weights of
copolymers are independent of increasing the contents of TCM and
MAAM. This result indicates that the polarity difference between
TCM and MAAM or MMA is relatively less than styrene and MAAM or
MMA [2,4], and does not make copolymerization difficult as styrene.
3.2. Thermal analyses
Fig. 1 display the DSC thermograms of poly(MMA-co-MAAM-co-
TCM) terpolymers and summarized results are listed in Table 1. All
Table 2
Kelen–Tudos parameters for (MMA þ MAAM) and for TCM.
X
Y
G
F
3
q
M1
M2
Q1
Q2
XðY ꢁ 1Þ
X2
Y
F
þ F
G
þ F
¼
¼
¼
¼
¼
¼
Y
g
g
M1 is the mole fraction of (MMA þ MAAM) and M2 is the mole fraction of TCM in
feed; Q1 and Q2 are their respective experimental mole fraction in the terpolymer.

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C.-T. Lin et al. / Polymer 51 (2010) 883–889
a
c
MMA-85
85-15-0
MMA-90
90-10-0
b
MMA-80
80-20-0
120.3
119.4
132.8
114.1
118.2
90-8-2
80-16-4
85-12-3
141.5
90-6-4
90-4-6
90-2-8
80-12-8
80-8-12
80-4-16
85-9-6
85-6-9
85-3-12
108.9
117.0
114.5
101.2
102.8
96.2
118.0
84.2
97.1
60
70
80
90
100
110
120
130
140
60
70
80
90
100
110
120
130
140
80
90
100
110
120
130
140
150
160
Temperature (ºC)
Temperature (ºC)
Temperature (ºC)
e
d
MMA-60
60-40-0
MMA-70
70-30-0
140.2
170.1
70-24-6
70-18-12
70-12-18
60-32-8
138.1
163.5
60-24-16
60-16-24
147.5
130.1
130.0
113.5
70-6-24
60-8-32
110.0
131.5
90
100
110
120
130
140
150
160
170
110
120
130
140
150
160
170
180
190
Temperature ( oC)
Temperature ( oC)
Fig. 1. DSC scans of poly(MMA-co-MAAM-co-TCM) copolymers at MMA contents of (a) 90, (b) 85, (c) 80, (d) 70 and (e) 60 mol%.
and thus lower hydrogen bonding content. However, at constant
80, 70 and 60 mol% of MMA, the fractions of hydrogen-bonded
carbonyl stretching of the composition of 80-16-4, 70-24-6 and
60-32-8 is comparable to that of 80-20-0, 70-30-0 and 60-40-0,
respectively, indicating that small replacement of TCM for MAAM
does not reduce the Tg of terpolymers. Decreasing small amount of
hydrogen bond donor does not decrease the fraction of hydrogen-
bonded carbonyl stretching of terpolymers substantially. However
the fraction of hydrogen-bonded carbonyl stretching of terpoly-
mers is decreased upon the excess addition of TCM units. Upon
increasing the replacement of TCM for MAAM, the fraction of inter-
associated hydrogen bonding between esters and amides decreases
slowly but the fraction of self-associated hydrogen bonding in
MAAM decreases sharply, indicating that the rigid bulky tricyclo-
decyl group of TCM units actually plays a role of inert diluent
segment to convert into inter-associative hydrogen bonding
between ester groups and amide groups from self-associative
hydrogen bonding in amide groups.
PMAAM
PMMA
The fraction of inter-associative hydrogen bonding between
polymer chains can affect the Tg [14] and the miscibility of a binary
polymer blend [15–17]. Upon increasing the fraction of inter-
associative hydrogen bonding in a binary polymer blend, the Tg can
be raised and the miscibility also can be enhanced [14,16].
Furthermore, the steric hindrance of bulky side group on hydrogen
bonding interaction not only reduces the fraction but also weakens
of hydrogen bond association [18,19]. To further understand the
effect of bulky TCM units in details, three compositions of 85-15-0,
80-16-4 and 60-16-24 possess similar MAAM and similar NH2
contents, implying that they have similar hydrogen-bonding donor
PTCM
1800
1750
1700
1650
1600
1550
Wavenumber (cm-1)
Fig. 2. IR spectra, displaying the range 1550–1800 cmꢁ1, of pure PMMA, PMAAM, and
PTCM.