Thermal Decomposition and Glass Transition Temperature of Poly(methyl Methacrylate) and Poly(isobutyl Methacrylate)

Abstract

The thermal decomposition and the glass transition temperatures of poly(methyl methacrylate) (PMMA) and poly(isobutyl methacrylate) (PiBuMA) were studied with a differential scanning calorimeter (DSC). The undecomposed and decomposed polymers were analyzed by gel permeation chromatography (GPC) for molecular weight distributions and by DSC for changes in the thermal properties and glass transition temperatures, T. In the isothermal decomposition of PMMA and PiBuMA, depolymerization reactions exclusively are operative. During low temperature decompositions, longer PMMA chains depolymerize first. These are followed by the shorter chains. In the case of PiBuMA, the shorter chains depolymerize first. Some of these undergo chain recombinations to yield very high molecular weight products. For identical values of weight loss, the respective decomposition temperatures for PiBuMA are 40 to 70 K lower than those for PMMA. The activation energies of decomposition (42 kJ/mol for PMMA and 67 kJ/mol for PiBuMA) have been found to be lower than those reported in the literature. Although T_g∞ of PiBuMA (331 K) agrees well with the literature value (326 K), T_g∞ of atactic PMMA (394 K) is higher than the reported value (378 K).     

Poly(phenyl methacrylate) and poly(1‐naphthyl methacrylate) prepared in microemulsions

Phenyl methacrylate and 1‐naphthyl methacrylate were polymerized in microemulsions using stearyltrimethylammonium chloride, cetyltrimethylammonium bromide, and a mixture of nonionic Triton surfactants to form latexes that were 20–30 nm in diameter. A temperature of 70 °C was needed to obtain polymers using thermal initiation. The tacticities of poly(phenyl methacrylate) (PPhMA) (55% rr) and poly(1‐naphthyl methacrylate) (P‐1‐NM) (47% rr) were the same as those of the polymers prepared in toluene solutions. The weight average molecular weights were 1 × 10⁶ and 5 × 10⁵ g/mol for PPhMA and P‐1‐NM prepared in microemulsions with very broad distributions. PPhMA samples from microemulsions and solution had the same T_g = 127 °C. P‐1‐NM from microemulsions had T_g = 145–147 °C compared with T_g = 142 °C for P‐1‐NM from solution. The molecular weights and the glass‐transition temperatures of both PPhMA and P‐1‐NM from microemulsions are substantially higher than any previously reported. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 519–524, 2001     

Additive Effects of Lithium Salts with Various Anionic Species in Poly (Methyl Methacrylate)

We report that lithium salts in lithium-ion batteries effectively modify the physical properties of poly (methyl methacrylate) (PMMA). The glass transition temperature (T_g) is an indicator of the heat resistance of amorphous polymers. The anionic species of the salts strongly affected the glass transition behavior of PMMA. We focused on the additive effects of various lithium salts, such as LiCF₃SO₃, LiCOOCF₃, LiClO₄, and LiBr, on the T_g of PMMA. The large anions of the former three salts caused them to form macroscopic aggregates that acted as fillers in the PMMA matrix and to combine the PMMA domains, increasing T_g. On the other hand, LiBr salts dispersed microscopically in the PMMA matrix at the molecular scale, leading to the linking of the PMMA chains. Thus, the addition of LiBr to PMMA increased T_g as well as the relaxation time in the range of glass to rubber transition.     

Poly(methyl methacrylate) copolymers containing multiple,pendent plasticizing groups

New ether dimer (ED‐Eh) and diester (EHDE) derivatives of α‐(hydroxymethyl)acrylate, each having two 2‐ethylhexyl side chains, and an amine‐linked di(2‐ethylhexyl)acrylate (AL‐Eh), having three 2‐ethylhexyl side chains, were synthesized and (co)polymerized to evaluate the effects of differences in the structures of the monomers on final (co)polymer properties, particularly glass transition temperature, T_g. The free radical polymerizations of these monomers yielded high‐molecular–weight polymers. Cyclopolymer formation of ED‐Eh and AL‐Eh was confirmed by ¹³C NMR analysis and the cyclization efficiencies were found to be very high (～100%). Copolymers of ED‐Eh, EHDE, and AL‐Eh with methyl methacrylate (MMA) showed significant T_g decreases over poly(methyl methacrylate) (PMMA) due to 2‐ethylhexyl side groups causing “internal” plasticization. Comparison of the T_g's of the copolymers of 2‐ethylhexyl methacrylate, ED‐Eh, EHDE, and AL‐Eh with MMA revealed that the impacts of these monomers on depression of T_g's are identical with respect to the total concentration of the pendent groups. This is consistent with an earlier study involving copolymers of monomers comprising one and two octadecyl side groups with MMA. That is, the magnitude of decrease in T_g's was quantitatively related to the number of the 2‐ethylhexyl pendent groups in the copolymers rather than their placement on the same or randomly incorporated repeat units. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2302–2310, 2010     

Synthesis and Properties of Novel Poly（amine ether）s

Using aromatic bis（4-bromophenyl） ether and various aromatic diamines as the monomers, a series of novel poly（amine ether）s （PAEs） have been synthesized via palladium-catalyzed aryl amination, which is the Hartwig-Buchwald polycondensation reaction. Their structures were characterized by means of elemental analysis, FT-IR, 1^H NMR and UV-Vis spectroscopy. The results show a good agreement with the proposed structures. Their general properties were studied by DSC and TG and it＇s obvious that they show high glass transition temperatures （Tg〉200 ℃）, good thermal stability with high decomposition temperatures （TD〉500℃） and excellent solubility. The mechanical behavior of these polymers suggested that they could be considered a new class of high-performance polymers.     

聚芳亚胺的合成、结构与性能

以不同的二碘化合物和芳香二胺为单体,通过两种不同的方法经缩聚反应得到了系列高分子量、低分布的聚芳亚胺。其结构由FT-IR, 1H NMR1和元素分析表征。由DSC和TG测定结果可知,该系聚合物具有较高的玻璃化转变温度(Tg＞150℃)和良好的热稳定性(TD＞400℃)。另外,该系聚合物还表现出良好的溶解性能。     

PHOTOPOLYMERS: SYNTHESIS AND CHARACTERIZATION OF POLY(4-CINNA-MOYLPHENYL METHACRYLATE) WITH GLYCIDYL METHACRYLATE

Copolymers of 4-cinnmoylphenyl methacrylate (CPMA) with glycidyl methacrylate were synthesized in methyl ethyl ketone solution using benzoyl peroxide as initiator at 70 ± 1°C. They were characterized by UV, IR, ¹H-NMR, and ¹³C-NMR spectra. Their compositions were determined by ¹H-NMR technique. The monomer reactivity ratios were determined by the Fineman-Ross and Kelen-Tüdös methods. The molecular weights ([Mbar]_w and [Mbar]_n) of the polymers were determined by GPC technique. Thermogravimetric analysis of the copolymers were carried out in air. The T_g of the polymers were determined by differential scanning calorimetry. The photocrosslinking properties of the homo and copolymers were also discussed.     

Vitamin C Functionalized Poly(Methyl Methacrylate) for Free Radical Scavenging

Abstract

In the present work, a strategy was developed to use mild and highly selective enzymatic methods to covalently couple the primary hydroxyl group of vitamin C with methyl methacrylate monomer, followed by a second enzymatic reaction catalyzed by horseradish peroxidase to polymerize the vinyl monomer yielding a vitamin C functionalized poly(methyl methacrylate) (PMMA). Vitamin C, L‐ascorbyl methylmethacrylate and PMMA, when used at concentrations up to 133 µM, fully scavenged 2,2‐diphenyl‐1‐picryl hydrazyl free radicals (0.2 mM). Thus, the formation of vinyl polymers with active pendent antioxidant compounds, in this case vitamin C, retained an ability to scavenge radicals while in polymeric form. The functionalized antioxidant on a PMMA backbone has implications for consumer‐related applications like foods, pharmaceuticals, and personal care products.     

Argon sorption and partial molar volume in poly(ethyl methacrylate) above and below the glass transition temperature

Sorption and dilation isotherms for argon in poly(ethyl methacrylate) (PEMA) are reported for pressures up to 50 atm over the temperature range 5–85°C. At temperatures below the glass transition (T_g=61°C), sorption isotherms are well described by the dual-mode sorption model; and isotherms above T_g follow Henry's law. However, isotherms for dilation due to sorption are linear in pressure at all temperatures over the range investigated. Partial molar volumes of Ar in PEMA are obtained from these isotherms. The volumes are approximately constant above T_g (about 40 cm³/mol), whereas the volumes below T_g are smaller and dependent on both temperature and concentration (19–26 cm³/mol). By analyzing the experimental data according to the dual-mode sorption and dilation model, the volume occupied by a dissolved Ar molecule and the mean size of microvoid in the glass are estimated to be 67 129 ų, respectively. The cohesive energy density of the polymer is also estimated as 61 cal/cm³ from the temperature dependence of the dual-mode parameters.     

Poly(methylene sebacate): Synthesis and characterization

The synthesis of poly(methylene sebacate) was carried out via the reaction of cesium sebacate with bromochloromethane in N-methylpyrrolidone over a range of temperatures (55–130°C). A number of polymers having limiting viscosity numbers in the range of 0.29–0.94 dL g^?1 (CHCl₃; 25°C) were characterized by elemental analyses, ¹H- and ¹³C-NMR, DSC, and GPC techniques. The polymerization was found to be very rapid at 100°C, being complete in ca. 15 min. and was relatively insensitive to the stoichiometric ratio of the monomers. As high molecular weight polymers were produced without the quantitative conversion of the reactants, the polymerization is considered to be occurring by an interfacial mechanism.     

Poly(methyl methacrylate)/Methacryl-POSS Nanocomposites with Excellent Thermal Properties

Poly(methyl methacrylate) (PMMA) nanocomposites containing (methacryloxy)propyl polyhedral oligomeric silsesquioxane (methacryl‐POSS) were prepared by bulk‐polymerization process. The structures of the products were characterized by FTIR, solid‐state NMR, TEM, XRD, DSC, TGA, XPS and UV‐Vis spectra. The hybrid materials were found to be largely homogeneous. DSC and TGA results indicate that the thermal properties of PMMA nanocomposites are significantly improved. The glass transition temperature (T_g) and thermal decomposition temperature (T_dec) of the nanocomposites increased by 58 and 110°C, respectively. The bulk hybrid material maintains excellent optical transparency in visible region.     

NOTE: Synthesis and Characterization of a Poly(acrylamide) with Pendant 1,4-piperazine-2,5-dione Moieties via Post-polymerization Cyclization

A poly(acrylamide) was synthesized from N ^α -Boc-N ^? -acrolyl-l-lysylglycine methyl ester via radical polymerization. This polymer typically had Mn ～ 100,000 g/mol, Mw ～ 300,000 g/mol, and a T_g of 93°C. Removal of Boc with TFA and cyclization with DABCO? in DMSO at 65°C afforded a soluble piperazinedione-containing polymer that had a T_g of 157°C and thermal stability up to 300°C. These results demonstrate a viable and efficient synthetic route to piperazinedione-containing polyacrylamides of high molecular weight. Related polymers that incorporate substituted indane moieties could be useful high T_g materials for fabrication of LC and NLO devices.     

Synthesis,Thermal Properties,and Thermoresponsive Behaviors of Cyclic Poly(2‐(dimethylamino)ethyl Methacrylate)s

This study aims at physicochemical properties of thermo‐ and pH/CO₂‐responsive cyclic homopolymers. Three examples of cyclic poly(2‐(dimethylamino)ethyl methacrylate)s (PDMAs) are synthesized by combining the reversible addition–fragmentation chain transfer process and the Diels–Alder ring‐closure reaction. After cyclization, the glass transition temperature significantly increases (ΔT_g = 51.8–59.7 °C) due to the different configurational entropy and end groups, and the maximum decomposition temperature to lose the pendent groups is drastically decreased from 309 to 278 °C. Effects of polymerization degree, polymer concentration, additive of NaCl, and pH/CO₂ on lower critical solution temperature behaviors of PDMA aqueous solutions are investigated. The cloud points (T_c) of ring PDMAs are usually higher than their linear precursors, and the ΔT_c values obtained under a fixed condition can reach up to 20.7 °C, revealing the crucial role of the topology effect. This study paves the way for unique properties and applications of smart cyclic polymers and their derivatives.

     

Effect of Tacticity of Poly(Methyl Methacrylate) on Conductivity of Poly(Ethylene Oxide)-Poly(Methyl Methacrylate) Blend-Based Polymeric Electrolytest

Abstract

Polymer electrolytes based on blends of poly(ethylene oxide) (PEO) with various stereoisomers of poly(methyl methacrylate) (PMMA) were studied by means of impedance spectroscopy and DSC. It was found that isotactic poly(methyl methacrylate) (1PMMA)-based electrolytes exhibit ambient temperature conductivities at least one order of magnitude higher than the electrolytes containing other stereoisomers of PMMA. The highest value of room temperature conductivity equal to 9 × 10^?5 S/cm was measured for a sample containing 30 wt% IPMMA. The effect observed results from the presence of a flexible amorphous phase in PEO-IPMMA blends which is favorable for fast ionic transport. A small increase of ionic conductivity with decreasing molecular weight of the added atactic poly(methyl methacrylate) was also observed.     

Longitudinal volume viscosity of poly(methyl methacrylate)

Volume flow of poly(methyl methacrylate) (PMMA) (M?_n = 43,000 and T_g = 384) has been measured in an Instron Capillary Rheometer. Elastic modulus of the longitudinal wave, longitudinal volume viscosity, initial longitudinal volume viscosity, and retardation times are described at temperatures above T_g (418–483K) and compression rates of about 1.00–200.00 × 10⁵ s^?1. An initial increase followed by a decrease in longitudinal volume viscosity has been observed as the compression rate increases and the volume deformation decreases, this last behavior being at the lowest values of the compression rate (6.0 and 30.0 × 10^?5 s^?1) a typical nonequilibrium one. η_L also increases with increasing temperature (T_g decreases 0.18°C/MPa), and volume flow activation energy decreases as the volume deformation increases.     

Poly(Alkyl Glycidate Carbonate)s as Degradable Pressure‐Sensitive Adhesives

Insertion of CO₂ into the polyacrylate backbone, forming poly(carbonate) analogues, provides an environmentally friendly and biocompatible alternative. The synthesis of five poly(carbonate) analogues of poly(methyl acrylate), poly(ethyl acrylate), and poly(butyl acrylate) is described. The polymers are prepared using the salen cobalt(III) complex catalyzed copolymerization of CO₂ and a derivatized oxirane. All the carbonate analogues possess higher glass‐transition temperatures (T_g=32 to ?5 °C) than alkyl acrylates (T_g=10 to ?50 °C), however, the carbonate analogues (T_d≈230 °C) undergo thermal decomposition at lower temperatures than their acrylate counterparts (T_d≈380 °C). The poly(alkyl carbonates) exhibit compositional‐dependent adhesivity. The poly(carbonate) analogues degrade into glycerol, alcohol, and CO₂ in a time‐ and pH‐dependent manner with the rate of degradation accelerated at higher pH conditions, in contrast to poly(acrylate)s.     

Synthesis,Characterization, and Functionalization of Hyperbranched Poly(ether ether ketone)s with Phenoxypheyl Side Group

Novel fluoride‐teminated hyperbranched poly(ether ether ketone) with 4‐phenoxyphenyl side group (HPEEK‐F) was prepared from 2‐(4‐phenoxyphenyl)‐1,4‐diphenol (A₂) and 1,3,5‐tris[4‐(4‐flourobenzoyl) phenoxy]benzene (B₃). An end‐capping approach was used to synthesize tertiary amino‐terminated fluorescent (HPEEK‐DMA) and phenyl ethynyl‐terminated self‐crosslinking poly(ether ether ketone)s (HPEEK‐PEP). These three polymers have the same backbone structure and degree of branching (DB=0.67), and different terminal groups. The nature of the terminal group was shown as the influences of the glass transition temperature (T_g) and decomposition temperature (T_d) of polymers. The T_g of HPEEK‐F and HPEEK‐DMA are 30°C lower than HPEEK‐PEP, whereas the T_d of HPEEK‐F are 90°C and 50°C higher than HPEEK‐DMA and HPEEK‐PEP, respectively. The HPEEK‐DMA fluoresce blue‐green in solid and in solution. This kind of hyperbranched polymer contains a large amount of terminal chromophore groups which can easily lead to the formation of intramolecular excimers. The fluorescence signal was decreased with increasing acidity, furthermore, the two peaks at 466 nm and 507 nm indicated a blue shift occurred. After curing, the HPEEK‐PEP displayed a T_g at 235.5°C, which is 100°C higher than original polymers. Thermally cured samples show good anti‐chemical corrodibility in DMF, THF, DMAc and NMP solvents.     

Synthesis and Photosensitive Properties of Poly(aryl imino) Containing Azobenzene Group (PAI-A)

Using 4,4′‐dibromobenzophenone and 4,4′‐diaminoazobenzene as monomers, poly(aryl imino) containing azobenzene unit (PAI‐A) was synthesized via palladium‐catalyzed amination, and structurally characterized by means of FT‐IR, ¹H NMR spectra and elemental analysis, the results of which show an agreement with the proposed structure. The UV absorption spectra were tested under different conditions. Additionally, differential scanning calorimetry (DSC) and thermogravimetric (TG) measurements show that PAI‐A possesses high glass transition temperature (T_g>176°C) and good thermal stability with high decomposition temperatures in nitrogen atmosphere (T_D>410°C).     

Activation of stable polymeric esters by using organo‐activated acyl transfer reactions

In this study, we succeeded in the in situ activation of nonactivated ester moieties embedded in polymer structures. Although poly(pentafluorophenyl methacrylate) (PPFPMA) can react with 2‐ethylhexylamine at 50 °C in the presence of proton scavenger such as NEt₃, such conditions were not suitable for poly(phenyl methacrylate) (PPhMA). Nevertheless, the combination of organo‐activating agents, namely 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) and 1,2,4‐triazole (TZ) led to a facile conversion from ester to amide for PPhMA. The reaction between PPhMA and 2‐ethylhexylamine was conducted at 120 °C in the presence of one equivalent of TZ and three equivalents of DBU and yielded >99% ester conversion to afford corresponding polymethacrylamide derivatives as confirmed by FT‐IR and ¹H NMR measurements. In addition, poly(2,2,2‐trifluoroethyl methacrylate) (PTFEMA) and poly(methyl methacrylate) (PMMA) were also allowed to react with amines in the presence of the organo‐activating agents with dramatically increased conversions (>70%). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1353–1358     

Poly(phenylethylnorbornene)s and their Hydrogenated Derivatives

Ring‐opening metathesis polymerization (ROMP) was used to synthesize novel ring‐opened poly[5‐(2‐phenylethylnorbornene)]. Hydrogenation can produce two different saturated derivatives, with the phenyl groups either preserved or saturated to cyclohexyl groups. These two different hydrogenated products allowed us to compare the effect of replacing the pendant phenyl groups with cyclohexyl groups on properties such as the glass transition temperature (T_g). We found that T_g decreased by only 2 °C (from 28 to 26 °C) upon replacement of the phenyl groups. This contrasts with the effect of saturating the phenyl groups in the addition polymer of 5‐(2‐phenylethylnorbornene), where the T_g increased by 34 °C, from 215 to 249 °C, a remarkable difference in magnitude and direction compared with the ROMP polymers.