Poly(methyl methacrylate) membranes

Uniform and symmetric membranes were formed from poly(methyl methacrylate) (PMMA) by making use of the stereocomplex phenomenon which characteristically occurs in the solution of a mixture of isotactic PMMA and syndiotactic PMMA. The water permeability of the membrane was very high compared to a commercially available cellulosic membrane, whereas their NaCl permeabilities were the same. The permeabilities of the membranes are explained by a simple capillary model. By varying the tacticity of the polymer it was found that the finest membrane structure is formed at the isotactic polymer ratio of ca. 30%. This shows the close relationship between complex formation and membrane permeability.     

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.     

聚甲基丙烯酸甲酯包覆纳米CaCO3改性聚氯乙烯研究

研究了聚甲基丙烯酸甲酯(PMMA)包覆纳米CaCO3复合粒子填充聚氯乙烯(PVC)复合材料的加工塑化和力学性能，并与未改性纳米CaCO3的改性效果进行比较。结果发现，填充纳米CaCO3使PVC平衡扭矩和平衡熔融温度均会有所提高，填充未改性碳酸钙增加更大，填充PMMA包覆CaCO3使材料冲击性能提高的幅度大于填充未改性纳米CaCO3，而拉伸强度下降幅度较小。当PMMA包覆CaCO3填充量为8％时缺口冲击强度增加到未改性PVC的194％。冲击缺口断面形态分析表明，采用PMMA包覆CaCO3时，纳米CaCO3在PVC基体中分散均匀、团聚少。     

Characterization and Properties of Poly(methyl methacrylate)/Graphene,Poly(methyl methacrylate)/Graphene Oxide and Poly(methyl methacrylate)/p-Phenylenediamine-Graphene Oxide Nanocomposites

In this study, poly(methyl methacrylate)/p-phenylenediamine-graphene oxide, poly(methyl methacrylate)/graphene, and poly(methyl methacrylate)/graphene oxide nanocomposite series were prepared using simple solution blending technique. In poly(methyl methacrylate)/p-phenylenediamine-graphene oxide series, graphene oxide modified with p-phenylenediamine was used to improve its dispersion and interfacial strength with matrix. Morphology study of poly(methyl methacrylate)/p-phenylenediamine-graphene oxide nanocomposite revealed better dispersion of p-phenylenediamine-graphene oxide flakes and gyroid patterning of poly(methyl methacrylate) over the filler surface. Due to nonconducting nature of graphene oxide, there was no significant variation in the thermal or electrical conductivity of these nanocomposites. Thermal conductivity of poly(methyl methacrylate)/p-phenylenediamine-graphene oxide 1.5 was 1.16 W/mK, while the electrical conductivity was found to be 2.3 × 10^?3 S/cm.     

Poly(vinylidene fluoride) - poly(methyl methacrylate) blends

A dynamic mechanical study of four blends of PVdF and PMMA plus the constituent homopolymers indicates that these two polymers are partly compatible, but that a crystalline PVdF phase also exists. The pure PVdF sample showed four transitions at ?95°, ?25° 75° and 100°C which are ascribed to a restricted chain motion of the Schatzki type, to a crystalline phase transition, to the glass transition and to premelting of poorly formed crystallites respectively. A longitudinal sonic velocity versus composition plot is interpreted in terms of the overall morphology of the blends whilst differential scanning calorimetry measurements are used to study crystalline melting.     

Relaxation of damped debye lattices: Poly(methyl methacrylate)

The damped Debye lattice model has been helpful in structuring molecular interpretations of viscoelastic relaxation in the primary transition region. Here, this model has been applied to the viscoelastic behavior of plasticized poly(methyl methacrylate) PMMA samples in the primary transition region. More than 25 samples using 11 different plasticizer systems were studied. The steepness indices of these samples remain experimentally indistinguishable from 1.0 inspite of the fact that substantial changes in characteristic temperatures were observed. These results on diluted PMMA lead to the conclusion that intermolecular interactions are dominant in these systems. If this is true, the model clearly predicts that further plasticization will be accompanied by a very distinctive variation of steepness index with plasticizer concentration.     

聚甲基丙烯酸甲酯热降解行为研究

采用热损失法研究了不同的工艺条件对聚甲基丙烯酸甲酯熟降解的影响和热降解动力学的研究,结果表明,聚甲基丙烯酸甲酯在氮气氛下热降解为1级反应.平均活化能为195.36 kJ/mol;在氧气氛下热降解分为2个阶段,反应前期为1.5级反应,反应中后期为1级反应.升温速率对2段式反应的温度划分有较大的影响.随着升温速率的提高,1.5级反应的温度区域增大.     

自聚甲基丙烯酸甲酯的结构及性能

通过核磁共振波谱、热失重分析仪、差示扫描量热仪及凝胶渗透色谱研究了自聚甲基丙烯酸甲酯(PMMA)的分子链结构、热稳定性、相对分子质量及其分布,并对PMMA的自引发聚合机理进行了探讨。结果表明,与引发剂引发合成PMMA相比,自聚PMMA的相对分子质量更高,分布更宽;自聚PMMA分子链内均含有热不稳定的过氧键,致使其在130 ℃便开始降解,但它对PMMA的热稳定性没有影响;自聚合是由氧与甲基丙烯酸甲酯单体（MMA）反应形成低相对分子质量过氧化物引发的。     

Poly(methyl methacrylate) and polyacrylonitrile dispersions stabilized by gelatin

Methyl methacrylate was polymerized in an aqueous medium in the presence of gelatin using potassium persulfate as initiator. The dispersion mode of polymerization, when the monomer is completely miscible with water, was investigated and compared with an emulsion process, which proceeds at higher monomer concentration. Spherical and relatively uniform polymer particles were formed. Macroscopic precipitation of polymer is prevented by combination of the steric stabilization by grafted gelatin and of repulsive electrostatic interactions from the initiator residues attached to the particle surface. Static and dynamic light scattering have been used to determine the molar mass (molar mass of the whole dispersion particle, M_wD ～ 10⁸-10⁹ g mol^?1) and hydrodynamic radius (R_hD ～ 50-120 nm) of the particles. The number of particles per unit volume does not depend on overall monomer concentration, and it is higher, and therefore the particle size is smaller, than that observed for the soapless emulsion polymerization. The addition of gelatin may be thus used to modify the particle size. Acrylonitrile dispersions were prepared under similar conditions. Unlike methyl methacrylate, this monomer does not swell the polymer particles. While poly(methyl methacrylate) particles are spherical and relatively uniform, the polyacrylonitrile dispersions consist of polydisperse aggregates of tiny polymer particles.     

Poly(methyl methacrylate) nanoparticles prepared through microwave emulsion polymerization

The emulsifier‐free emulsion polymerization of methyl methacrylate (MMA) was conducted with microwave irradiation. Superfine and monodisperse poly(methyl methacrylate) (PMMA) microspheres were obtained. Microwave irradiation notably promoted the polymerization reaction. This phenomenon was ascribed to the acceleration of the initiator [potassium persulfate (KPS)] decomposition by microwave irradiation. The experimental results revealed that the apparent activation energy of KPS decomposition decreased from 128.3 to 106.0 kJ/mol with microwave irradiation. The average particle size of the prepared PMMA latex was mainly controlled with the MMA concentration; it increased linearly from 103 to 215 nm when the MMA concentration increased from 0 to 0.3 mol/L and then remained almost constant at MMA concentrations of 0.3–1.0 mol/L. The KPS concentration had no effect on the average particle size, but the particle size dispersity was significantly reduced by a high KPS concentration. With a mixed polymerization phase (water/acetone = 1:3 v/v) or a redox initiation system, PMMA nanoparticles were obtained with an average particle size of 45 or 67 nm, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2815–2820, 2004     

Poly(methyl methacrylate)–epoxy vitrimer composites

In this study, we synthesized poly(methyl methacrylate) (PMMA) epoxy vitrimer composites by doping methyl methacrylate (MMA) and benzoyl peroxide into a curing system of epoxy resin and citric acid. The vitrimer composites were characterized with dynamic mechanical thermal analysis, scanning electron microscopy, and stress‐relaxation and lap‐shear testing. The test results show that with increasing amount of MMA, the existence of PMMA in the epoxy vitrimer matrix in the form of intermiscible, slightly soluble, and phase separation became more evident. When the doping amount of PMMA reached 10–25 wt %, the bonding strength of the PMMA–epoxy vitrimer composites was about two times that of the epoxy vitrimer (from 2.3 to 4.3 MPa). This showed that the self‐healing strength of the vitrimer composites was better than that of the pure vitrimer. When the PMMA in the epoxy matrix was in a slightly soluble form, the linear PMMA improved the mechanical properties of the epoxy vitrimer by physical winding. At the same time, the doping of PMMA promoted the transesterification rate of the epoxy vitrimer and enhanced the bonding strength of the composites without lowering the epoxy vitrimer glass‐transition temperature. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46307.     

Damping Properties of Polyorganosiloxane/Poly(methyl methacrylate) Interpenetrating Networks

Interpenetrating polymer networks (IPNs) based on polyorganosiloxane/poly(methyl methacrylate) were prepared via sequential polymerization and the damping and mechanical properties of these materials were studied. The effects of crosslinking in both the first‐ and second‐formed networks were investigated. The experimental results show that the extent of damping of the IPNs was decreased and shifted to higher temperature as the content of poly(methyl methacrylate) was increased; the mechanical properties such as tensile strength and hardness (Shore A) were increased with increasing poly(methyl methacrylate) (PMMA) content. The loss factor peak becomes narrower with increasing crosslinker level in the first‐formed network (polysiloxane network), while increasing crosslinker content in the second‐formed network (PMMA network) results in a broadening of the IPN transition peak and moves the IPN transition to higher temperatures as well.     

Synthesis and Surface Properties of Poly(methyl methacrylate)/Poly(ethylene glycol) Binary Brushes

A new kind of binary polymer brushes was synthesized from two immiscible polymers, PMMA and PEG, on GPS‐modified silicon wafers. Surface composition, layer thickness, coverage, chain density, wetting ability, morphology and protein adsorption of the binary brushes were investigated by XPS, ellipsometry, AFM and contact angle measurements. The results show that both PMMA and PEG were successfully grafted onto the surface. The surface coverage and the chain density of PMMA and PEG brushes can be controlled by modulating the reaction temperature and time. This kind of binary polymer brushes exhibits a distinct microphase‐separated structure and excellent protein‐preventing property.

     

Physical Properties of Plasticized Poly(vinyl chloride) Blended with Poly(methyl methacrylate) Nanoparticles Synthesized by Differential Microemulsion Polymerization

In this work, poly(methyl methacrylate) (PMMA) nanoparticles synthesized by differential micro emulsion polymerization were used to improve the physical properties of plasticized poly(vinyl chloride) (PVC). PVC, plasticizer (40 phr), heat stabilizer (2 phr), and lubricant (0.2 phr) were melt-mixed with varied amount of the PMMA nanoparticles (3, 5, 7, and 9 phr) on a two-roll mill, followed by compression molding. The results showed that the tensile strength, Young's modulus, tear strength, and thermal stability were improved, but the elongation at break deteriorated with increased PMMA content. Moreover, the flammability of the plasticized PVC was not improved by the PMMA nanoparticles.     

抗冲击改性剂ACR增韧有机玻璃的研究

通过熔融共混的方法在PMMA中混入不同用量的抗冲击改性剂ACR,制得PMMA/ACR共混物,并进行了力学性能和断面形态分析.结果表明,随着ACR用量的增加,改性PMMA的缺口冲击强度不断增加,而拉伸强度和弯曲强度则成下降趋势.当ACR质量分数为5%时,改性PMMA的缺口冲击强度比未改性的提高了42.42%.     

线型低密度聚乙烯溶液接枝聚甲基丙烯酸甲酯

用溶液接枝聚合的方法在线型低密度聚乙烯(LLDPE)上接枝聚合极性单体甲基丙烯酸甲酯(MMA)制备LLDPE-g-PMMA,研究了反应时间、单体用量和引发剂用量对接枝反应的影响。结果表明,随着引发剂和单体量的增加,聚合物的接枝率增加,当引发剂质量分数为0.48%,单体比率为150%时,接枝率将达到26.1%。利用红外光谱(FTIR)、核磁共振碳波谱仪(13C-NMR)对其进行结构表征,证明PMMA分子链被接枝聚合到LLDPE上。使用X射线衍射仪(XRD)、差示扫描量热仪(DSC)对接枝聚合物的结晶性能进行了分析,发现接枝聚合没有改变晶型,但结晶焓由61.39 J/g降低到47.18 J/g。     

含磷不饱和酯改性有机玻璃的制备及性能

以磷酸三乙酯、乙二醇和甲基丙烯酸为原料,通过脱烷基化和酯化两步法合成含磷不饱和酯,并利用红外光谱对这种含磷不饱和酯进行结构表征。将这种含磷不饱和酯以不同比例加入到甲基丙烯酸甲酯单体中制备改性有机玻璃,并对这种有机玻璃的透光率、极限氧指数、冲击强度、玻璃化温度进行测试。结果表明:改性后的有机玻璃的阻燃性能大幅提高,且随着含磷不饱和酯含量的增大而增高;冲击强度和玻璃化温度随着不饱和酯含量的增大先增高后降低。     

Poly(methyl methacrylate) as masking material for microelectromechanical system (MEMS) fabrication

In the present study direct current (dc) sputtered poly(methyl methacrylate) (PMMA) films deposited on silicon substrates were evaluated as masking materials for anisotropic etching of silicon in aqueous potassium hydroxide (KOH) and tetramethyl ammonium hydroxide (TMAH) solutions. Sputtered PMMA films were characterized by FTIR to ascertain the bonding, by X‐ray photoelectron spectroscopy (XPS) for the elemental composition, and by the contact angle for measuring the adhesion of the film with the substrate. FTIR and XPS data showed the presence of a poly(tetrafluoroethylene)‐like film on the silicon substrate. The interfacial tension was calculated from the contact angle value, which was 0.82 dyne/cm, confirming good adhesion of the film and the substrate. A pattern was lithographically transferred through the masking material on the silicon substrate, and the etch rate of the masking layer was calculated from the masking time data of the films. The etch rate value of 4 Å/min obtained for the masking material is low compared to the etch rate of the conventional masking materials (60 Å/min for SiO₂ and 8 Å/min for Si₃N₄). © 2006 Wiley Periodicals Inc. J Appl Polym Sci 102: 2094–2098, 2006     

Clay Nanotube/Poly(methyl methacrylate) Bone Cement Composites with Sustained Antibiotic Release

Orthopedic‐grade PMMA bone cement, admixed with prophylactic antibiotics, is widely used in hip and knee replacement surgery. There is a critical need to improve its structural integrity and to control antibiotic release. In this study, clay nanotubes are loaded with the antibiotic gentamicin sulfate and the cement is doped with 5–8 wt% nanotubes. The halloysite nanotubes isolate the drug from the cement monomers and serve as nanocontainers for sustained release of the antibiotic. Gentamicin‐loaded clay nanotubes admixed in PMMA cement provide sustained release up to 300–400 h and with enhanced release at cement cracks. The PMMA/halloysite/gentamicin composite tensile strength does not deteriorate as compared with pure cement and its adhesion to bone is significantly increased.

     

Poly(ethylene oxide)/poly(methyl methacrylate) blends: Influence of tacticity of poly(methyl methacrylate) on blend structure and miscibility

The influence of different configurations of poly(methyl methacrylate) on the miscibility and superstructure of poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blends was examined using small-angle X-ray scattering and differential scanning calorimetry. The blends prepared by solution casting were isothermally crystallized at 48°C. The miscibility, the melting behaviour, the glass transition temperature and the structural parameters of the blends were strongly dependent on the tacticity and blend composition. The small-angle X-ray intensity profiles were analysed using a recently developed methodology. For the poly(ethylene oxide)/atactic poly(methyl methacrylate) (PEO/APMMA) and poly(ethylene oxide)/syndiotactic poly(methyl methacrylate) (PEO/SPMMA) blends, the long period and the amorphous and transition region thicknesses increased with increase of PMMA content, whereas for the poly(ethylene oxide)/isotactic poly(methyl methacrylate) (PEO/IPMMA) blends they are independent of composition. The structural properties of the blends were attributed to the presence of non-crystallizable material in the interlamellar or interfibrillar regions, depending on PMMA tacticity. From the glass transition and melting temperatures, it has been supposed that one homogeneous amorphous phase is present in the case of PEO/APMMA and PEO/SPMMA blends and that the PEO/IPMMA amorphous system is phase-separated. The free-volume contribution to the energy of mixing for the various tactic PMMAs is hypothesized to be responsible for the difference in mixing behaviour.