Mono-acrylated isosorbide as a bio-based monomer for the improvement of thermal and mechanical properties of poly(methyl methacrylate)

Article abstract of DOI:10.1039/c9ra07548h

Despite its optical clarity and good weatherability, poly(methyl methacrylate) (PMMA) cannot meet the needs of special occasions due to its deficient thermal and mechanical properties. To overcome these shortcomings, a type of novel bio-based monomer, mono-acrylated isosorbide, was used as a comonomer for the poly(methyl methacrylate) via a solution polymerization process. The chemical structure, the thermal and mechanical properties of the copolymerized PMMA were characterized. When the molar content of the mono-acrylated isosorbide was increased from 0% to 15%, the glass transition temperature T_g of the copolymerized PMMA was increased from 151.2 °C to 172.5 °C, and the initial decomposition temperature (T_5%) was increased from 323.1 °C to 396.3 °C. Moreover, the impact strength of copolymerized PMMA increased from 10.59 kJ m^-2 to 17.19 kJ m^-2 and the tensile strength improved from 84.02 MPa to 97.56 MPa when the mono-acrylated isosorbide was incorporated with different contents. The incorporation of rigid and thermally stable isosorbide could contribute to the improved thermal and mechanical properties of PMMA, which would find important applications in the military and aeronautical materials under harsh service environments.

Full text of DOI:10.1039/c9ra07548h

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PAPER
Mono-acrylated isosorbide as a bio-based
monomer for the improvement of thermal and
mechanical properties of poly(methyl
methacrylate)
Cite this: RSC Adv., 2019, 9, 35532
a
Juan Zhao,b Wenjuan Wang,b Jingjie Qia and Yi Hub
*
Dinghua Yu,
Despite its optical clarity and good weatherability, poly(methyl methacrylate) (PMMA) cannot meet the
needs of special occasions due to its deficient thermal and mechanical properties. To overcome these
shortcomings,
a type of novel bio-based monomer, mono-acrylated isosorbide, was used as
a comonomer for the poly(methyl methacrylate) via a solution polymerization process. The chemical
structure, the thermal and mechanical properties of the copolymerized PMMA were characterized. When
the molar content of the mono-acrylated isosorbide was increased from 0% to 15%, the glass transition
temperature Tg of the copolymerized PMMA was increased from 151.2 ꢀC to 172.5 ꢀC, and the initial
decomposition temperature (T5%) was increased from 323.1 ꢀC to 396.3 ꢀC. Moreover, the impact
strength of copolymerized PMMA increased from 10.59 kJ mꢁ2 to 17.19 kJ mꢁ2 and the tensile strength
improved from 84.02 MPa to 97.56 MPa when the mono-acrylated isosorbide was incorporated with
different contents. The incorporation of rigid and thermally stable isosorbide could contribute to the
improved thermal and mechanical properties of PMMA, which would find important applications in the
military and aeronautical materials under harsh service environments.
Received 18th September 2019
Accepted 15th October 2019
DOI: 10.1039/c9ra07548h
rsc.li/rsc-advances
inorganic nanoller. In addition, a difficult blending process is
required to acquire the even-distributed composite. Therefore,
Introduction
the copolymerization modication with a special comonomer
could be a promising protocol to improve the thermal and
mechanical performance without sacricing the optical
properties.
Since the early 20th century, plastic materials have become
increasingly indispensable, and are widely used in all aspects of
modern life because of their outstanding properties.1,2 As a type
of optical functional polymer, poly(methyl methacrylate)
(PMMA) has been extensively employed in various applications,
such as batteries, electromagnetic shielding, optics, light-
emitting devices, and corrosion-resistant coating. These wide
applications are mainly due to the outstanding properties of the
PMMA materials, such as excellent optical clarity, exceptional
dimensional stability, chemical resistance, and good weather-
ability.3 However, it has relatively weak thermal stability and
decient mechanical properties, which have been huge stum-
bling blocks for extending its further applications.4 In order to
overcome these shortcomings, many types of research have
incorporated nanoparticles in a polymeric matrix. The used
nanoller includes carbon nanotube,5–7 montmorillonite,8 and
SiO2 nanoparticles.9 Although the nanoller could improve the
mechanical performance, the optical clarity and other proper-
ties of PMMA could deteriorate with the introduction of the
Being the focus of the polymer industry for the last decade,
the utilization of bio-renewable feedstocks has produced many
renewable building blocks with a special structure, which could
be used to create novel polymer materials. For example, 2,5-
furandicarboxylic acid derived from carbohydrates can substi-
tute petroleum-derived terephthalic acid and be used to
synthesize bio-based plasticizers and polyesters with many
outstanding properties.10,11 Bio-based long-chain diacid and
diamine are also type of important monomers for bio-based
polyamide, which has attracted broad interest due to
numerous outstanding advantages, such as high strength,
toughness, corrosion resistance and wears resistance.12–14
Therefore, bio-renewable feedstocks, including carbohydrates,
triglycerides, and proteins, could bring new opportunities for
the development of a novel functional polymer.15,16
1,4:3,6-Dianhydro-D-glucitol isosorbide can be produced
from starch via chemical–biological processes, including enzy-
matic hydrolysis to glucose, chemical hydrogenation to sorbitol
and chemical dehydration to isosorbide. Due to the typical
advantages, such as rigidity, high thermal stability, renewability
aCollege of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University,
Nanjing 211816, China. E-mail: yudh@njtech.edu.cn; Fax: +86-25-58139389; Tel:
+86-25-58139386
bCollege of Pharmaceutical Science, Nanjing Tech University, Nanjing 211816, China
35532 | RSC Adv., 2019, 9, 35532–35538
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and non-toxicity, isosorbide has been used to prepare poly- phase liquid was separated and dried by anhydrous calcium
esters, polyethers, polyurethanes, polycarbonates, poly- chloride. Other reagents were used as received without further
phosphonates, polytriazoles, and so on.17–24 For example, purication.
because of its non-toxicity, isosorbide has been used as
a substitution for bisphenol A in polycarbonates and epoxy
resins particularly for applications in contact with food.25 In
Synthesis of mono-acrylated isosorbide
other applications, isosorbide has been used as a comonomer
As shown in Scheme 1, the direct esterication of isosorbide
to increase the glass transition temperature (Tg) and thermal
was performed using p-toluenesulfonic acid as a catalyst in
stability of polyesters such as PET and PBS,23 which could
a typical Dean-Stark apparatus. In order to minimize the poly-
broaden the high-temperature applications of polyesters such
merization of acrylic acid itself, hydroquinone was used as the
as the moulded parts or packaging materials.
inhibitor. In a typical experiment, a given amount of puried
Comparing with the direct use as a diol and cross-linking
isosorbide and toluene (water carrier) were added into a round
monomer, mono-vinyl isosorbide derivatives have been re-
bottom ask. Aer isosorbide has melted aer heating, 1.8% of
ported only in a few works of literature.26–32 These mono-vinyl
p-toluenesulfonic acid (wt% based on total reactants) was added
isosorbide monomers are especially useful and could nd
into the ask. Then, the acrylic acid containing 0.1% hydro-
important applications in the construction of polymers with
quinone (wt%) was added dropwise into the ask. In order to
designed architectures through chain-growth polymerizations.
minimize the di-acrylated isosorbide formation, the molar ratio
For example, Beghdadi et al.31 reported that the substitution of
of the acrylic acid to isosorbide was xed at 1 : 1. The reaction
the vinyl triazole moiety at either the endo- or exo-position had
proceeded at 100 ꢀC for 4 h. Aer cooling to room temperature,
a signicant effect on the glass transition temperature Tg and
the crude products were washed using a saturated solution of
solubility of the polymer. Polymers prepared from a monomer
NaHCO3 to remove unreacted acrylic acid, isosorbide, hydro-
with the vinyl triazole group at the ꢀexo-position were insoluble
quinone and p-toluenesulfonic acid, and the oil phase was
in water and possessed a Tg ¼ 118 C, whereas those prepared
further washed by saturated NaCl solution and dried over
from a monomer with vinyl triazole at the endo-position were
anhydrous Na2SO4. The crude product was further puried via
water-soluble and showed a Tg ¼ 71 ꢀC. However, there are few
ash column chromatography (eluent: methanol/acetone ¼
reports on PMMA modied with mono-vinyl isosorbide for
3 : 1, v/v). The typically isolated yield based on isosorbide was
improving the thermal and mechanical performance.
82.5–85.6%.
In this study, the special bio-based mono-vinyl monomer,
mono-acrylated isosorbide (MAI), was synthesized through
direct esterication of the isosorbide and acrylic acid with p-
toluenesulfonic acid as the catalyst. Then, the copolymerized
Free radical polymerization of MAI and MMA
As shown in Scheme 2, mono-acrylated isosorbide was used as
a comonomer for copolymerization with the puried MMA.
During the solution polymerization, chloroform was used as the
solvent. In a typical experiment, 0.1 mol puried methyl
methacrylate and a given amount of mono-acrylated isosorbide
(mol%, based on MMA) was dissolved into 50 mL chloroform,
and the solution was transferred into a round bottom ask.
Aer the reactants solution was heated to 70 ꢀC, 1% benzoyl
peroxide initiator (wt% based on total reactants) of chloroform
solution was added slowly. Then, the reactant mixtures were
PMMA samples were prepared through solution polymerization
with different molar contents of mono-acrylated isosorbide. The
polymer structures were studied by Fourier transform infrared
1
spectroscopy (FTIR) and H nuclear magnetic resonance spec-
troscopy (NMR) techniques. The thermal and mechanical
properties of the copolymerized PMMA materials were charac-
terized by simultaneous thermal analysis, differential scanning
calorimetry (DSC), dynamic mechanical analysis (DMA), impact
strength and tensile strength experiments. The potential rela-
tionship between structure and performance was discussed.
ꢀ
heated to 80 C and remained for 5 h. The un-reacted mono-
mers and chloroform in the solution were rotary evaporated
under vacuum. The acquired solid products were rinsed by
acetone and methanol for three times and were dried at 40 C
Experimental methods
Materials
ꢀ
under vacuum. Typically the isolated yield of the polymer based
on the total monomer weight is 85.8–89.3%. Similar to the
parent PMMA, copolymerized PMMA samples with mono-
acrylated isosorbide show the 90–92% transmittance in the
visible region (400–700 nm).
Isosorbide (98%) was obtained from the Hongbaifeng Industry
and trade Co., Ltd. (Jinan, China). Sodium chloride, sodium
bicarbonate, acrylic acid (99%, inhibited with 200 ppm mono-
methyl ether hydroquinone) and methyl methacrylate (98%,
inhibited with 250 ppm mono-methyl ether hydroquinone)
(MMA) were bought from Aladdin Co. Shanghai, China. p-Tol-
uenesulfonic acid, chloroform, benzoyl peroxide, hydroqui-
none, methanol, acetone, toluene, and CDCl3 were acquired
from Sinopharm Chemical Reagent Co., Ltd. Prior to the
experiments, isosorbide was puried through ethyl acetate
recrystallization. Methyl methacrylate was washed to remove
the inhibitor by a 5% solution of sodium hydroxide. The oil Scheme 1 Synthesis of mono-acrylated isosorbide.
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Mechanical properties. The Charpy impact strength was
evaluated using an impact test machine (XCJ-4, Chengde,
China) according to ISO 179-1-2001. The experimental impact
strength was 1 J, and the specimens span was 40 mm. Each
sample was determined repeatedly for ve times, and the
average impact strength value was the nal result.
The tensile strength was determined on the universal
mechanical tester (Instron Co. Shimadzu GE-I). The standard
dumbbell-shaped specimens were prepared via casting
methods. The experimental speed was 5 mm minꢁ1. Each
sample was determined repeatedly for ve times to obtain the
reliable average value.
Scheme 2 Free radical copolymerization of methyl methacrylate and
mono-acrylated isosorbide.
Results and discussion
Structural analysis of mono-acrylated isosorbide
The structure of mono-acrylated isosorbide was characterized
via FTIR and 1H NMR, and the corresponding results are shown
in Fig. 1. In order to compare the characteristic absorption, di-
acrylated isosorbide (DAI) is also shown in Fig. 1(A). As shown in
Fig. 1(A), the characteristic peak at 1730 cmꢁ1 could be ascribed
to the stretching vibration of –C]O bond, and the absorption at
1270 cmꢁ1 and 1180 cmꢁ1 could be ascribed to the stretching
vibration of –C–O–C– bond, which indicates that ester bond was
formed. The C]C bond stretching vibration of the acrylate
groups was observed at 1635 cmꢁ1, and the absorption at
3080 cmꢁ1 could be induced by the –C–H stretching vibration of
Properties characterization
Structure characterization. The molecular weight and poly-
dispersity index (PDI) of copolymerized PMMA were determined
via gel permeation chromatography (GPC), which was per-
formed on Wyatt system equipped with an SSI 1500 pump and
a Waters Styragel HR 2.5 mm, 300 mm ꢂ 7.8 mm column.
Chloroform (1.0 mL minꢁ1) was used as the eluent at 30 ꢀC
using commercial polystyrene standards for calibration.
1H NMR (600 MHz) spectra were recorded on a Bruker
Avance-III600 spectrometer in CDCl3 with tetramethylsilane
(TMS) as the internal reference.
FTIR spectra were recorded on an Avatar 360 FTIR spec-
trometer from Nicolet with DTGS KBr as the detector. The
sample was mixed together with KBr powder and tableted into
a thin round piece. The piece was then scanned in the range of
4000–400 cmꢁ1
.
Thermal properties. Differential scanning calorimetry was
performed using a dynamic scanning calorimeter (PerkinElmer,
DSC/DSC7). The material was coꢁol1ed down from ambient to
ꢁ30 ꢀC with a ramp of ꢁ5 ꢀC min and maintained at ꢁ30 ꢀC
for 30 min to ensure its thermal equilibrium. Then, the analysis
was registered under air at a heating rate of 5 C minꢁ1. The
ꢀ
glass transition temperature (Tg) of these copolymerized PMMA
samples was obtained from the peak of the heat ow curves.
The simultaneous thermal analysis was performed using
a thermogravimetric analyzer (TGA) from Netzsch Instruments
(NETZSCH, 409PC). Samples of 5–10 mg were placed in a plat-
ꢁ1
ꢀ
ꢀ
ꢀ
inum pan and heated from 20 C to 800 C at a 10 C min
ramp under an inert N2 atmosphere.
The dynamic mechanical analysis was evaluated using
a dynamic mechanical analyzer (TA Instruments, DMA Q800).
The rectangular specimen (20.0 mm (L) ꢂ 5.0 mm (W) ꢂ
0.1 mm (T)) was made by casting the polymers in a mould. The
DMA spectra were recorded in the temperature range of 30–
300 ꢀC at a 5 ꢀC minꢁ1 ramp. The mechanical loss factor (tan d)
has been recorded as a function of temperature. All the
measurements were performed at a frequency of 1 Hz. The glass
transition temperature (Tg) of this modied PMMA has been
acquired from the peak of the loss factor curves.
Fig. 1 FTIR and 1H NMR spectra of mono-acrylated isosorbide. (A)
FTIR; (B) H NMR.
1
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–C]C–H groups, which demonstrates that an acrylate group velocity and the nal polymer molecular weights. Therefore, the
has been introduced into the products. Comparing with DAI effect of the ratio of MAI to MMA on molecular weight and PDI
monomer, the MAI monomer showed an obvious absorption has been studied by the GPC method and the corresponding
peak at 3500 cmꢁ1, which could be ascribed to the –O–H results have been listed in Table 1. Comparing with the parent
stretching vibration of isosorbide.
PMMA, the copolymerized PMMA samples with mono-acrylated
The 1H NMR results shown in Fig. 1(B) demonstrate the isosorbide showed lower molecular weights and higher PDI
structure of mono-acrylated isosorbide. The chemical shi at values. On the other hand, with the increase in the mono-
6.40–6.43 ppm, 5.77–5.81 ppm, and 6.01–6.06 ppm could be acrylated isosorbide content, the copolymerized samples
ascribed to the proton 1, 2 and 3 of the vinyl group. The showed a decrease in the molecular weight and increase in the
chemical shi at 5.43–5.48 ppm, 4.29–4.34 ppm, 4.17–4.19 ppm, PDI value, which indicates that MAI has lower reactivity than
3.39–3.52 ppm and 4.79–4.81 ppm could be induced by the MMA.
protons located at the isosorbide rings. The chemical shi at
1H NMR technique was used to study the structure of the
4.7–4.73 ppm could be ascribed to the proton of free hydroxyl parent and copolymerized PMMA, and the corresponding
from the mono-acrylated isosorbide. These results indicate that results are shown in Fig. 3. From Fig. 3(A), the chemical shi at
mono-acrylated isosorbide was synthesized successfully.
0.80–0.89 ppm and 0.92–1.01 ppm could be ascribed to the
proton 1 and 2 of the methylene group in the parent PMMA. The
broad chemical shi at 1.8–2.0 ppm could be ascribed to the
proton of the methyl group. The strong chemical shi at 3.56–
3.60 ppm could be induced by the protons of methyl linked to
the ester bond. In comparison, Fig. 3(B) shows more compli-
cated chemical shi peaks. The chemical shi at 4.43–4.45 ppm
could be ascribed to the proton 1 of the isosorbide hydroxyl
group. The chemical shi at 3.84–3.86 ppm and 3.98–4.00 ppm
could be ascribed to the proton 2 and 5 of the isosorbide ring.
The chemical shi at 4.51–4.53 ppm could be ascribed to the
proton 3 of the methylene group in isosorbide. These results
demonstrate that the copolymer of MAI and MMA was synthe-
sized successfully. According to the qualitative calculation, the
actual content of mono-acrylated isosorbide is 7.12% in the
PMMA-8%MAI samples, lower than the theoretical value, which
could be induced by the slower polymerization rate of the
mono-acrylated isosorbide.
Polymer structural analysis
In order to demonstrate the incorporation of mono-acrylated
isosorbide, FTIR and 1H NMR were used to study the struc-
ture of polymers. As shown in Fig. 2, the strong absorption at
1735 cmꢁ1 could be ascribed to the stretching vibration of –C]
O bonds, and the absorption at 1150 cmꢁ1 could be ascribed to
the stretching vibration of –C–O–C bonds, which indicates that
the ester bonds exist in the polymer. Two samples did not show
absorption at 1635 cmꢁ1, which is the typical absorption of –C]
C, indicating that the acrylate monomers have been polymer-
ized totally. The absorption at 2990 cmꢁ1 could be ascribed to
saturated C–H stretching vibration, and the absorption at
1470 cmꢁ1 and 1390 cmꢁ1 could be ascribed to the deformation
vibration of –CH2–CH2– and –CH3. It is a remarkable fact that
there was a new medium absorption peak at 3630 cmꢁ1 for
PMMA-8%MAI sample, compared with the parent PMMA. This
absorption peak could be ascribed to the stretching vibration of
the hydroxyl group located in the MAI monomer, which
demonstrates that the MAI monomer was introduced into the
skeleton of PMMA.
Thermal properties
Fig. 4 shows the TG and the corresponding DTG curves of the
parent and copolymerized PMMA samples. The weight loss
value of 5% was chosen as the reasonable criterion to evaluate
the onset of the thermal degradation of each sample, and the
results are listed in Table 2.
Mono-acrylated isosorbide could copolymerize with other
vinyl monomers through free radical polymerization, but the
rigid block of isosorbide could inuence the polymerization
It was observed from the TG curves in Fig. 4(A) that all of the
PMMA samples were thermally stable in the N2 atmosphere
below 250 ꢀC and were seen to undergo a one-stage thermal
degradation process above this temperature. According to
Czech's report,33 the PMMA could degrade via a homolytic
Table
1 Experimental molecular weight of PMMA-MAI polymer
samples
Samples
n(MAI) : n(MMA)
Mw
Mn
PDI
PMMA
0
78 326
74 213
69 856
70 684
76 358
71 426
73 892
55 799
54 152
51 974
55 736
50 657
1.02
1.33
1.29
1.36
1.37
1.41
PMMA-2%MAI
PMMA-5%MAI
PMMA-8%MAI
PMMA-10%MAI
PMMA-15%MAI
2 : 100
5 : 100
8 : 100
10 : 100
15 : 100
Fig. 2 FTIR spectra of parent PMMA and PMMA-8%MAI.
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Table 2 Glass transition temperature and thermal stability of parent
PMMA and PMMA-MAI samples
Tg (ꢀC)
(DMA)
Tg (ꢀC)
(DSC)
PMMA-MAI polymers
T5% (ꢀC)
Tmax (ꢀC)
PMMA
151.2
158.4
163.6
164.7
167.3
172.5
152.0
158.6
164.2
165.1
168.0
173.0
323.1
341.9
360.0
378.5
388.1
396.3
370.2
390.5
400.7
421.4
429.9
445.1
PMMA-2%MAI
PMMA-5%MAI
PMMA-8%MAI
PMMA-10%MAI
PMMA-15%MAI
mechanisms due to the incorporation of isosorbide structure
blocks.
From Fig. 4 and the data in Table 2, T5% and Tmax for the
parent PMMA was about 323 ꢀC and 370.2 ꢀC under the classical
temperature ramp b of 10 C minꢁ1, respectively. For general
ꢀ
commercial resins, Tmax is higher than 400 ꢀC to meet polymer
processing requirements.34,35 With the increase in the amount
of mono-acrylated isosorbide from 2% to 5%, 8%, 10% and
15%, the corresponding degradation temperature T5%
increased from 342 ꢀC to 360 ꢀC, 379 ꢀC, 388 ꢀC and 396 ꢀC.
Moreover, the maximum degradation temperature Tmax has
Fig. 3 1H NMR spectra of samples. (A) Parent PMMA; (B) PMMA-8%
MAI.
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
increased from 370 C to 391 C, 401 C, 421 C, 430 C, and
ꢀ
445 C. These results indicate that the thermal stability of the
copolymerized PMMA with the mono-acrylated isosorbide has
obviously improved, which could be ascribed to the high
thermal stability of the isosorbide. More signicantly, these
results demonstrate clearly that the copolymerization with
mono-acrylated isosorbide could improve the thermal stability
of the PMMA resins, meeting the thermal stability requirement
of high-temperature commercial resins.
Fig. 5 shows the DSC curves of the parent and copolymerized
PMMA samples, and the calculated glass transition temperature
(Tg) are listed in Table 2. From Fig. 5, all of the samples showed
a similar peak shape regardless of the MAI amount, and the
tendency to shi to a higher temperature has been observed.
Fig. 4 Thermal analysis profiles of parent PMMA and PMMA-MAI.
polymer chain cleavage, followed by monomer unzipping.
Comparing with the sharp downstream decomposition curve of
the parent PMMA sample, the copolymerized PMMA samples
showed gentle downstream decomposition curves and the
typical narrower decomposition temperature ranges, which
indicate that the copolymerized PMMA samples have under-
gone complicated decomposition via different decomposition
Fig. 5 DSC profiles of parent PMMA and PMMA-MAI.
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Table 3 Mechanical properties of parent PMMA and PMMA-MAI
samples
As shown in Table 2, the glass transition temperature (Tg)
has increased from 152.0 ꢀC to 158.6 ꢀC, 164.2 ꢀC, 165.1 ꢀC,
ꢀ
ꢀ
168.0 C and 173.0 C with the MAI increasing from 0 to 15%.
The dynamic mechanical analysis was employed to investi-
gate the variation of the Tg and mechanical properties of the
parent PMMA and copolymerized PMMA as the temperature
changes, and the results are shown in Fig. 6. As usual, the
temperature corresponding to the tan d peak maximum is taken
as Tg, and the results are listed in Table 2. From Table 2, the
glass transition temperature (Tg) calculated from the DMA and
DSC curves are very similar. The introduction of mono-acrylated
isosorbide could enhance the intermolecular interactions of
PMMA chains and increase the free volume of PMMA. There-
fore, the incorporation of the mono-acrylated isosorbide
decreased the mobility of the PMMA chains, which presented as
the increase of glass transition temperature Tg. According to
Jannasch's viewpoint,36 the improved glass transition tempera-
ture (Tg) value for the polymers containing mono-vinyl iso-
sorbide could originate from the combination of the rigid
bicyclic structure and the hydrogen bond of the isosorbide
monomers. As shown in Fig. 6, it is clear that each sample has
only one tan d peak, indicating that the copolymerized PMMA is
a thermodynamically compatible copolymer. Besides, the peak
width of tan d could be related to the miscibility between the
comonomers, and the narrow peak indicates good miscibility
between different blocks of copolymers. From the DMA curves
in Fig. 6, the tan d peak becomes gentler and wider with the
increase in the MAI amount, indicating that mono-acrylated
isosorbide with the PMMA chain has lower miscibility, which
could be induced by the free hydroxyl group of isosorbide.
Samples
Impact strength/kJ mꢁ2
Tensile strength/MPa
PMMA
10.59 ꢃ 0.85
13.24 ꢃ 0.6
15.08 ꢃ 0.78
16.51 ꢃ 0.89
16.97 ꢃ 1.21
17.19 ꢃ 0.93
84.02 ꢃ 2.83
89.13 ꢃ 3.25
93.19 ꢃ 2.49
95.76 ꢃ 4.22
94.26 ꢃ 3.68
92.3 ꢃ 3.82
PMMA-2%MAI
PMMA-5%MAI
PMMA-8%MAI
PMMA-10%MAI
PMMA-15%MAI
95.76 MPa. According to Wissinger's standpoint,37 a higher
tensile strength could originate from denser polymer chain
packing and stronger intramolecular interactions. When the
MAI monomer was copolymerized with MMA, the hydroxyl
group of the isosorbide block enhanced further interaction
among the polymer chains, which could contribute to the
improved tensile strength. When the MAI content was improved
further to 10% and 15%, the tensile strength of the copoly-
merized PMMA decreased to 94.26 MPa and 92.3 MPa. The
introduction of excessive MAI monomer to the PMMA chain
could induce the highly branched PMMA chains, increased the
distance between the polymer chains, and weakened the inter-
actions between the chains, which could contribute to the
decreased tensile strength.
From Table 3, the impact strength of the parent PMMA was
observed as 10.59 kJ mꢁ2, and the copolymerized PMMA-2%
MAI showed 13.24 kJ mꢁ2, increased by 25.02%. When the MAI
amount was improved further from 5% to 8%, 10%, and 15%,
the copolymerized PMMA samples showed an improved impact
strength from 15.08 kJ mꢁ2 to 16.51 kJ mꢁ2, 16.97 kJ mꢁ2, and
17.19 kJ mꢁ2, respectively. Comparing with the linear PMMA
chain, the incorporation of MAI with the free hydroxyl group
increased the intramolecular interactions via a hydrogen bond.
These enhanced interactions could inhibit the chain cleavage,
improve impact strength, and contribute to a better toughness,
which are in agreement with the results reported by Tu et al.38 In
addition, the introduction of a fused ve-member rings of iso-
sorbide into the PMMA linear chains has increased the free
volume of the polymer chains, which could further improve the
PMMA toughness.
Mechanical properties
The mechanical properties of the parent and copolymerized
PMMA are presented in Table 3. As shown in Table 3, the parent
PMMA showed a tensile strength of 84.02 MPa. Interestingly,
the tensile strength of the copolymerized PMMA-2%MAI was
89.13 MPa, which increased by 6.08%. With the increase in the
mono-acrylated isosorbide from 5% to 8%, the tensile strength
of the copolymerized PMMA increased further to 93.19 MPa and
Conclusion
In summary, a novel bio-based mono-vinyl monomer was
synthesized with isosorbide as the core scaffold. With the
mono-acrylated isosorbide as a comonomer, the thermal and
mechanical properties of PMMA could be improved obviously.
The introduction of the isosorbide block as PMMA side chains
could inhibit the polymer chain exibility, and enhance the
interactions among PMMA chains via a hydrogen bond,
increasing the free volume of PMMA chains, which could
contribute to the improved thermal and mechanical properties.
Overall, the results of this study show that the mono-vinyl
monomer of isosorbide can be used to improve the thermal
and mechanical properties of PMMA, which could nd
Fig. 6 DMA profiles of parent PMMA and PMMA-MAI samples.
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Conflicts of interest
There are no conicts to declare.
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Acknowledgements
The authors are grateful for the nancial support by the
National Natural Science Foundation of China (No. 21376120),
the National Key Technology R&D Program (No.
2012BAD32B08), and Six Talent Peaks Project in Jiangsu Prov-
ince (No. 2018-GDZB-196).
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35538 | RSC Adv., 2019, 9, 35532–35538
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