Synthesis and thermal properties of poly(methyl methacrylate)‐poly(L‐lactic acid)‐poly(methyl methacrylate) tri‐block copolymer

Poly(methyl methacrylate)‐poly(L ‐lactic acid)‐poly(methyl methacrylate) tri‐block copolymer was prepared using atom transfer radical polymerization (ATRP). The structure and properties of the copolymer were analyzed using infrared spectroscopy, gel permeation chromatography, nuclear magnetic resonance (¹H‐NMR, ¹³C‐NMR), thermogravimetry, and differential scanning calorimetry. The kinetic plot for the ATRP of methyl methacrylate using poly(L ‐lactic acid) (PLLA) as the initiator shows that the reaction time increases linearly with ln[M]₀/[M]. The results indicate that it is possible to achieve grafted chains with well‐defined molecular weights, and block copolymers with narrowed molecular weight distributions. The thermal stability of PLLA is improved by copolymerization. A new wash‐extraction method for removing copper from the ATRP has also exhibits satisfactory results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polymerization‐induced phase separations in branched poly(methyl methacrylate) synthesis

Methyl methacrylate and ethylene glycol dimethacrylate or 1,6‐hexanediol dimethacrylate (HDDMA) were copolymerized in the presence of a nonsolvent (heptane) for poly(methyl methacrylate) (PMMA) to examine the phenomenon of polymerization‐induced phase separations (PIPS) in branched PMMA synthesis. The process was dependent upon the amount of nonsolvent and crosslinker in the reaction mixture. Gel particles were obtained in the majority of phase‐separated systems, and their formation was promoted by the preferential partition of monomer and crosslinker into the precipitated polymer phase during the phase separation process. Experimental data showed that, because of its lower solubility parameter, HDDMA can be used as crosslinker to minimize gel particle formation in systems where PIPS is present. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1462–1468, 2005     

Characterization by dilute solution and rheological methods of polystyrene and poly(methyl methacrylate) produced with a tetrafunctional peroxide initiator

Polystyrene (PS) and poly(methyl methacrylate) (PMMA) samples produced by the bulk homopolymerization of styrene and methyl methacrylate with a tetrafunctional peroxide initiator (JWEB50) are characterized in detail by various solution and rheological methods. For comparison purposes, “linear” PS and PMMA samples were produced under similar conditions with a monofunctional initiator (TBEC). The four sample types were characterized by size exclusion chromatography (SEC) setups to determine molecular weight, radius of gyration, and intrinsic viscosity distributions. Contraction factors were calculated and indicated evidence of branching for polystyrene produced with JWEB50 while no such effects were observed with PMMA. The rheological behavior of the samples was subsequently investigated by performing oscillatory shear and creep experiments. Compared to the “linear” material, samples produced with JWEB50 exhibited a reduction in zero‐shear viscosity that was attributed to long‐chain branching. Retardation spectra were calculated based on creep data and converted to dynamic compliances that were then combined with the oscillatory data. This provided master curves spanning a much wider frequency range than could be obtained experimentally. Examination of various viscoelastic functions showed evidence of long‐chain branching for both polystyrene and poly(methyl methacrylate) samples produced with JWEB50. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1340–1355, 2007     

Synthesis and characterization of poly(methyl methacrylate) using monofunctional polyhedral oligomeric silsesquioxane as an initiator

POSS/PMMA composite was synthesized by atom transfer radical polymerization (ATRP) at 110 °C using commercial POSSCl as an initiator and CuCl/2,2′-bipyridine as catalyst system. The structures of POSS/PMMA and POSSCl were characterized by Fourier transfer infrared spectroscopy, Nuclear magnetic resonance spectroscopy, Ger permeation chromatography, X-ray diffraction and X-ray photoelectron spectroscopy, which confirmed that Si–Cl bond on POSS cage could successfully initiate the ATRP of methyl methacrylate, so there is only one POSS unit in a PMMA chain. The thermal properties of POSS/PMMA were investigated by Differential scanning calorimetry and Thermogravimetric analysis, the results show that the incorporation of POSS cage results in the enhancement of the glass transition temperature and the decomposition temperature of PMMA, which is mainly attributed to the mono-dispersion of POSS in PMMA matrix at molecular lever.     

Surface‐initiated atom‐transfer radical polymerization (SI‐ATRP) of methyl methacrylate from carbon fibre

Surface modification of carbon fibre (CF) by well‐defined polymer brushes was carried out using the ‘grafting from’ method. Poly(methyl methacrylate)‐grafted carbon fibre (CF‐PMMA) was successfully prepared by surface‐initiated atom‐transfer radical polymerization (SI‐ATRP) of methyl methacrylate (MMA) from the macro‐initiator, bromo‐acetic ester‐modified carbon fibre (CF‐BrA), with the complex of 1,10‐phenanthroline and Cu(I)Br as catalyst. The percentage of grafting (PG%) and the conversion of monomer (C%) increased linearly with increasing of polymerization time, and reached 24.0 % and 6.7 %, respectively, after a polymerization time of 6 h, calculated from the elemental analyses (EA). The structural and surface morphological analyses were conducted with Fourier‐transform infrared (FTIR) spectroscopy, X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Copyright © 2005 Society of Chemical Industry     

悬浮聚合法制取不同分子量级别的聚甲基丙烯酸甲酯

采用粉状MgCO3 作为分散剂 ,悬浮聚合制取了分子量从 2 4× 10 4 ～ 2 5 4× 10 4 的聚甲基丙烯酸甲酯。考察了温度、引发剂种类和浓度、分子量调节剂、转化率对聚合物分子量的影响规律 ,用粘度法测量了聚合物聚甲基丙烯酸甲酯 (PMMA)的分子量。结果表明 :温度的升高、引发剂浓度的增大、分子量调节剂的加入都会导致分子量的减小 ,随着转化率的提高 ,聚合物的分子量增大。在同等条件下 ,引发剂过氧化苯甲酰 (BPO)聚合所得的分子量较偶氮二异丁腈 (AIBN)高。通过实验 ,得到了满足作者需求的分子量 (96× 10 4 ～ 10 0× 10 4 )的聚合物的聚合条件为 :分散剂MgCO3 用量 1% ,单体∶水相 =1∶2 5 (质量比 ) ,引发剂BPO浓度 0 5 % ,反应温度 70℃ ,反应时间 3h。     

Synthesis and properties of poly(methyl methacrylate)/carbon nanotube composites covalently integrated through in situ radical polymerization

Poly(methyl methacrylate) (PMMA)/single‐walled carbon nanotube (SWNT) composites were synthesized by the grafting of PMMA onto the sidewalls of SWNTs via in situ radical polymerization. The free‐radical initiators were covalently attached to the SWNTs by a well‐known esterification method and confirmed by means of thermogravimetric analysis and Fourier transform infrared spectroscopy. Scanning electron microscopy and transmission electron microscopy were used to image the PMMA–SWNT composites; these images showed the presence of polymer layers on the surfaces of debundled, individual nanotubes. The PMMA–SWNT composites exhibited better solubility in chloroform than the solution‐blended composite materials. On the other hand, compared to the neat PMMA, the PMMA–SWNT nanocomposites displayed a glass‐transition temperature up to 6.0°C higher and a maximum thermal decomposition temperature up to 56.6°C higher. The unique properties of the nanocomposites resulted from the strong interactions between the SWNTs and the PMMA chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Increased sensitivity of multiwalled carbon nanotube network by PMMA functionalization to vapors with affine polarity

Multiwalled carbon nanotube network (MWCNT‐N)/poly(methyl methacrylate) (PMMA ) composite is prepared by solution radical polymerization. The entangled multiwall carbon nanotube network (MWCNT‐N) is obtained by vacuum filtration and functionalized by allyl isocyanate to form polymerizable vinyl groups on a nanotube surface. The solution polymerization binds PMMA covalently to these groups and yields MWCNT‐N/PMMA composite manifesting electrical conduction and selective chemical vapor sensing. The latter property is evaluated in terms of affinity of organic solvent vapor and PMMA polarities. It is found that the affinity of acetone polarity with polarity of PMMA improves significantly the sensitivity of the composite to this solvent while the sensitivity to methanol is the same and to iso‐pentane even decreased in comparison with the corresponding property of MWCNT‐N. The composite selective response is favorable for a possible composite use as a sensing element and/or vapor switch. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and characterization of poly(methyl methacrylate) grafted sago starch using potassium persulfate as redox initiator

In this article, the graft copolymerization of methyl methacrylate (MMA) onto sago starch (AGU) was carried out in aqueous medium using potassium persulfate (PPS) under nitrogen gas atmosphere. The maximum percentage of grafting achieved was 90% under optimized conditions of reaction temperature, monomer, PPS, AGU, and reaction period corresponding to 50°C, 47 mmol, 1.82 mmol, 6.17 × 10^?3 mol L^?1, and 1.5 h, respectively. The grafting of MMA onto sago starch was confirmed by the differences in infrared spectroscopy. The viscosity measurement and the average molecular weight determination were estimated using Huggin's and Mark Houwink's equations, respectively. This material may have application as a biodegradable plastic. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1891–1897, 2004     

Synthesis and characterization of poly(methyl methacrylate)/montmorillonite nanocomposites by in situ bulk polymerization

Poly(methyl methacrylate)/montmorillonite (MMT) nanocomposites were prepared by in situ bulk polymerization. The results showed that the silicone coupling agent affected the structure and properties of hybrid materials. XRD analysis showed that the dispersion of clay in nanocomposites with silicone‐modified organophilic MMT was more ordered than that in nanocomposites with unmodified organophilic MMT. The glass transition temperature (T_g) of the nanocomposites was 6–15°C higher and the thermal decomposition temperature (T_d) was 100–120°C higher than those of pure PMMA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2256–2260, 2003     

Preparation and characterization of poly(vinylidene fluoride) nanocomposites containing multiwalled carbon nanotubes

Poly(vinylidene fluoride) (PVDF) nanocomposites with different loadings of multiwalled carbon nanotubes (MWNT) were prepared by melt‐compounding technique. A homogeneous dispersion of MWNT throughout PVDF matrix was observed on the cryo‐fractured surfaces by scanning electron microscopy. Thermogravimetric analysis results indicated that the thermal stability of neat PVDF was improved with the incorporation of MWNT. Dynamic mechanical analysis showed a significant improvement in the storage modulus over a temperature range from ?125 to 75°C with the addition of MWNT. The melt‐rheological studies illustrated that incorporating MWNT into PVDF matrix resulted in higher complex viscosities (|η*|), storage modulus (G′), loss modulus (G″), and lower loss factor (tan δ) than those of neat PVDF. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Graft copolymerization of methyl methacrylate upon gelatin initiated by benzoyl peroxide in aqueous medium

The graft copolymerization of methyl methacrylate upon gelatin was studied using benzoyl peroxide as an organic initiator in aqueous medium. The grafting reactions were carried out within the 65–90°C temperature range, and the effect of monomer and initiator concentrations on the graft yield were also investigated. The maximum graft yield was obtained at a benzoyl peroxide concentration of 0.20 × 10⁻² mol/L and the optimum temperature was 80°C. Thermogravimetric analysis showed that the thermal stability of gelatin increased as a result of grafting. Further, such changes in the properties of methyl methacrylate‐grafted gelatin as density, moisture regain, and water uptake were also determined. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1547–1556, 1999     

Grafting of partially hydrolysed poly(methyl methacrylate) onto mesylated cellulose acetate

A new synthetic route to cellulose graft polymers by nucleophilic displacement of mesylate groups from mesyl cellulose acetate (MCA) by the polystyrylcarboxylate anion has been recently reported by us. This approach to cellulosic graft polymers overcomes the drawbacks of the radical polymerization methods and allows for precise control of parameters such as the molecular weight and molecular weight distribution of the grafted side chains, higher degree of substitution on the cellulose backbone, the number and nature of grafted side chains and overall better control and reproducibility of the grafting process. In this report, partially hydrolysed poly(methyl methacrylate) was successfully grafted on to mesylated cellulose acetate in excellent yields by nucleophilic displacement of mesylate groups in less than 60 min at 75°C.     

Grafting of poly(methyl methacrylate) or polyacrylonitrile onto polystyrene using ATRP technique

One of the most useful methods for synthesizing the graft and well‐defined copolymers is the atom transfer radical polymerization (ATRP) method. The polymerization was initiated by polystyrene (PS) carrying chloroacetyl groups as macroinitiator, in the presence of copper chloride (CuCl) and bipyridine (bpy). The macroinitiator (chloroacetylated PS) was prepared by successive chloroacetylation of PS under mild conditions and these reaction conditions overcome the problem of gelation and crosslinking in polymers. Successful graft copolymerizations were performed with methyl methacrylate (MMA) in toluene at 80°C and with acrylonitrile (AN) in tetrahydrofuran/ethylenecarbonate (62.5/37.5 v/v %) mixed solvent at 55°C. The characterization of the copolymers was investigated by ¹H‐NMR and FT‐IR spectroscopices. Gel permeation chromatography measurement indicated an increase of the molecular weight of the graft copolymers, as compared to that of the macroinitiator. This measurement also indicated the monomodal molecular weight distribution. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2619–2627, 2006     

Poly(methyl methacrylate)-block-polysulfide-block-poly(methyl methacrylate) copolymers obtained by free-radical polymerization combined with oxidative coupling

Summary Poly(methyl methacrylate)-block-polysulfide-block-poly(methyl methacrylate) copolymers were synthesized for the first time through a new method involving the free radical polymerization of MMA in the presence of a thiocol oligomer as a chain transfer agent, followed by chemical oxidation of the remaining SH end-groups. The chain transfer constant of the SH end-groups of the thiocol was estimated from the rate of consumption of the thiol groups versus the rate of consumption of the monomer (C_T=0.67). The triblock copolymers synthesized were characterized by SEC and ¹H NMR measurements.     

Comparison of the phase behaviour of the liquid-crystalline polymer/poly(methyl methacrylate) and poly(vinyl acetate)/poly(methyl methacrylate) blends

The phase behaviour of blends of a liquid-crystalline polymer (LCP) and poly(methyl methacrylate) (PMMA), as well as the phase state of blends of PMMA and poly(vinyl acetate) (PVA) has been investigated using light scattering and phase-contrast optical microscopy. The blends of LCP and PMMA have been obtained by coagulation from ternary solutions. The cloud point curves were determined. It was established that both pairs demix upon heating, ie have an LCST. In the region of intermediate composition, the phase separation proceeds according to a spinodal mechanism; however for LCP/PMMA blends, the decomposition proceeds according to a non-linear regime from the very onset. In the region of small amounts of LCP, the phase separation follows a mechanism of nucleation and growth. For PMMA/PVA blends, the spinodal decomposition proceeds according to a linear regime, in spite of the molecular mobility that PVA chains develop at lower temperatures. Only after prolonged heat treatment does the process transit to a non-linear regime. The data show a similarity between the phase behaviour of blends of liquid-crystalline and of flexible amorphous polymers. The distinction consists of the absence of a linear regime of decomposition for LCP-PMMA blends. © 1999 Society of Chemical Industry     

Preparation and characterization of poly(methyl methacrylate) beads

The phase behavior of Poly(ethylene terephthalate)/Poly(ethylene‐2,6‐naphthalate)/Poly(ethylene terephthalate‐co‐ethylene‐2,6‐naphthalate) (PET/PEN/P(ET‐co‐EN)) ternary blends in molten state was evaluated from differential scanning calorimetry (DSC) and NMR results as well as optical microscopic observations. Copolymer of ethylene terephthalate and ethylene‐2,6‐naphthalate was prepared by a condensation polymerization, which was a random copolymer with an intrinsic viscosity (IV) of 0.3 dL/g. The phase diagram of the ternary blends revealed that the miscibility of ternary blends in molten state was dependent on the fraction of P(ET‐co‐EN) in the blends and holding time of the blends at high temperatures above 280°C. With increase in the holding time, the fraction of copolymer in the blends necessary to induce the immiscible to miscible transition decreased. For the blends with longer holding time at 280°C, the phase diagram in molten state was irreversible against the temperature, although a reversibility was found for the blends with short holding time of 1 min at 280°C. The irreversibility of phase behavior was not explained simply by the increase of copolymer content produced during heat treatment. Complex irreversible physical and chemical interactions between components and change of phase structure of the blend in the molten state might influence on the irreversibility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

聚苯乙烯-聚甲基丙烯酸甲酯核-壳粒子的制备

由种子乳液聚合法制备了聚苯乙烯-聚甲基丙烯酸甲酯核-壳粒子。以过硫酸钾(KPS)为引发剂,辛基酚聚氧乙烯醚(OP-10)为乳化剂,合成了聚苯乙烯(PS)种子核;连续滴加甲基丙烯酸甲酯(MMA),在核表面富集MMA,制备了粒径范围在0.16~0.67μm的核-壳粒子;当单体苯乙烯与甲基丙烯酸甲酯(St/MMA)的比为30∶70(质量比)时,所得粒径在0.18μm,粒径分布为0.012。差示扫描量热(DSC)研究显示,复合粒子的玻璃化转变温度(Tg)为97.2℃,峰形单一,表现出良好的热性能。     

Phase behavior and properties of poly(methyl methacrylate)/poly(vinyl acetate) blends prepared via in situ polymerization

Polymer blends composed of poly(methyl methacrylate) (PMMA) and poly(vinyl acetate) (PVAc) were prepared via radical-initiated polymerization of methyl methacrylate (MMA) in the presence of PVAc. Differential scanning calorimetry and dynamic mechanical analysis were employed to investigate the miscibility and phase behavior of the blends. The PMMA/PVAc blends of in situ polymerization were found to be phase separated and exhibited a two-phase structure, although some chain transferring reaction between the components occurred. The phase separation resulted from the solvent effect of MMA during the in situ polymerization, which was confirmed by the investigation of phase behavior based on solution cast blending. Solubility analysis of the polymerized blends indicated that some chain transferring reaction between the components occurred during the polymerization. An abrupt increase in gel content from 21.2 to 72.4 wt % was observed when the inclusion of PVAc increased from 30 to 40 wt %, and the gel component consisted of the component polymers as shown by infrared spectroscopy studies. The thermogravimetric analysis study indicated that the inclusion of a small amount of PVAc gives rise to a marked stabilization effect on the thermal stability. The PMMA/PVAc blends exhibited increased notched impact properties with the inclusion of 5 wt % PVAc. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 675–684, 1998     

Effect of tacticity of poly(methyl methacrylate) on the miscibility with poly(vinyl pyrrolidone)

Isotactic, atactic, and syndiotactic poly(methyl methacrylates) (PMMA) (designated iPMMA, aPMMA, and sPMMA) with approximately the same molecular weight were mixed separately with poly(vinyl pyrrolidone) (PVP) primarily in chloroform to make three polymer blend systems. Differential scanning calorimetry (DSC) was used to study the miscibility of these blends. The results showed that the tacticity of PMMA has a definite impact on its miscibility with PVP. The aPMMA/PVP and sPMMA/PVP blends were found to be miscible because all the prepared films showed composition-dependent glass-transition temperatures (T_g). The glass-transition temperatures of the aPMMA/PVP blends are equal to or lower than weight average and can be qualitatively described by the Gordon–Taylor equation. The glass-transition temperatures of the other miscible blends (i.e., sPMMA/PVP blends) are mostly higher than weight average and can be approximately fitted by the simplified Kwei equation. The iPMMA/PVP blends were found to be immiscible or partially miscible based on the observation of two glass-transition temperatures. The immiscibility is probably attributable to a stronger interaction among isotactic MMA segments because its ordination and molecular packing contribute to form a rigid domain. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3190–3197, 2001