Study of poly(methyl methacrylate)/poly(ethylene oxide) blends in solution. I

Determination of polymer-polymer interaction parameters (b₂₃) has been made by viscometry for poly(methyl methacrylate)/poly (ethylene oxide) blends, in solution, of a wide range of molecular weights of both polymers. The results obtained show that the compatibility of the polymer pair PMMA/PEO in 1.2-dichloroethane depends not only on the molecular weight of the samples used but also on the concentration of one polymer in relation to another.     

Compatibility studies of natural rubber/poly(methyl methacrylate) blends by viscometry and phase separation techniques

The compatibility of binary blends of natural rubber (NR) and poly(methyl methacrylate) (PMMA) has been analysed from the viscosity behaviour. For this, the equations developed by both Krighbaum and Wall, and their modified forms by Williamson and Wright, were used. The interaction between polymers in solution has been interpreted qualitatively based on the heat of mixing (ΔH) and interaction parameter (X1). Viscometry and spectroscopy studies and calculation of the heat of mixing and the interaction parameter indicated the heterogeneous nature of NR/PMMA blends. The effects of graft copolymer of natural rubber and poly(methyl methacrylate) (NR-g-PMMA) as an emulsifying agent on the interfacial properties of NR/PMMA blends were studied based on the phase separation behaviour. The demixing behaviour is found to be a function of graft copolymer concentration, mode of mixing, nature of solvent and molecular weight of homopolymers and graft copolymers. The demixing behaviour has been studied by noting the phase separation time and volume of the phase separated region. The addition of graft copolymer decreases the demixing behaviour of the blends. This revised version was published online in November 2006 with corrections to the Cover Date.     

嵌段共聚物增容共混聚合物的相形貌及胶束迁移行为研究

主要研究了对称性的聚苯乙烯-聚甲基丙烯酸甲酯嵌段共聚物(PS-b-PMMA,简称SM)对聚甲基丙烯酸甲酯/聚甲基丙烯酸环己酯(PMMA/PCHMA)熔融共混体系的增容。采用透射电子显微镜(TEM)表征了SM和PMMA分子量对共混体系微观相形态和胶束迁移行为的影响。研究表明,SM分别在PMMA与PCHMA均聚物中形成不同结构的胶束,当SM在PMMA/PCHMA界面上形成"湿刷"时,SM在PCHMA相中形成的胶束才能迁移到PMMA相中。SM的加入改善了PMMA与PCHMA之间的相容性,但其增容效果取决于SM的分子量。随着分散相PMMA分子量从19kg/mol增加到39kg/mol,PMMA粒子的平均粒径逐渐增加。     

Nonspherical dented poly(methyl methacrylate)/poly(styrene-co-divinylbenzene) particles formed in seeded soap-free emulsion copolymerization

In this study, nonspherical poly(methyl methacrylate)/poly(styrene-co-divinylbenzene) [PMMA/P(St-co-DVB)] particles having multiple dents on the surface were prepared by seeded soap-free emulsion copolymerization of St and DVB (used as a crosslinker) on spherical linear PMMA seed particles. The effect of various polymerization parameters on particle morphology, as well as polymerization kinetics and morphological evolution, were investigated in detail. It was found that, to prepare this kind of nonspherical particles, it was necessary to conduct the polymerization at a relatively low temperature, using batch monomer addition mode and PMMA seed of relatively high molecular weight. The formation of the nonspherical particles was attributed to the phase separation between the second-stage monomers and the crosslinked P(St-co-DVB) network being formed during polymerization.     

Lens epithelial cell response to atmospheric pressure plasma modified poly(methylmethacrylate) surfaces

Selective control of cellular response to polymeric biomaterials is an important consideration for many ocular implant applications. In particular, there is often a need to have one surface of an ophthalmic implant capable of promoting cell attachment while the other needs to be resistant to this effect. In this study, an atmospheric pressure dielectric barrier discharge (DBD) has been used to modify the surface region of poly(methyl methacrylate) (PMMA), a well established ocular biomaterial, with the aim of promoting a controlled response to human lens epithelial cells (LEC) cultured thereon. The DBD plasma discharge environment has also been employed to chemically graft a layer of poly(ethylene glycol) methyl ether methacrylate (PEGMA) onto the PMMA and the response to LEC likewise determined. Two different molecular weights of PEGMA, namely 1000 and 2000 MW were used in these experiments. The LEC response to DBD treated polystyrene (PS) samples has also been examined as a positive control and to help to further elucidate the nature of the modified surfaces. The LEC adhered and proliferated readily on the DBD treated PMMA and PS surfaces when compared to the pristine polymer samples which showed little or no cell response. The PMMA and PS surfaces that had been DBD grafted with the PEGMA₁₀₀₀ layer were found to have some adhered cells. However, on closer inspection, these cells were clearly on the verge of detaching. In the case of the PEGMA₂₀₀₀ grafted surfaces no cells were observed indicating that the higher molecular weight PEGMA has been able to attain a surface conformation that is capable of resisting cell attachment in vitro.     

Microspherical poly(methyl methacrylate)/multiwalled carbon nanotube composites prepared via in situ dispersion polymerization

In this study, microspherical poly(methyl methacrylate)/multi-walled carbon nanotube (PMMA/ MWCNT) composites were directly prepared by in situ dispersion polymerization using poly (N-vinylpyrrolidone) in methanol media. PMMA/MWCNT microspheres having a diameter of 2.6 approximately 3.9 microm and a molecular weight of 58,000 approximately 65,000 g/mol with a 15.7 approximately 19.5% coefficient of variation (Cv) were synthesized. The morphology of the synthesized composite was investigated using scanning electron microscopy and transmission electron microscopy. The experimental results demonstrated that MWCNTs are well dispersed and embedded in the final PMMA/MWCNT microspheres. The prepared PMMA/MWCNT microspheres were investigated in terms of their capacity to serve as an electrorheological (ER) materials.     

两亲接枝共聚物PMMA-g-PEO溶液性质及在反相乳液聚合中的应用

核磁共根(^1H—NMR)、透射电镜(TEM)和粘度测定法的结果表明两亲接枝共聚物聚甲基丙烯酸甲酯接枝聚氧乙烯(PMMA—g—PEO)在甲苯中可形成胶束，PMMA—g-PEO的浓度和体系的温度决定量胶束的大小及CMC值。将PMMA—g-PEO应用于丙烯酰胺的反相乳液聚合，结果表明，可形成稳定的乳液。PMMA—g—PEO用量越大，丙烯酰胺的聚合速率越快，乳液粒径和稳定性越大。     

Processing and properties of poly(methyl methacrylate)/carbon nanofiber composites

Single wall carbon nanotubes, multiwall carbon nanotubes, as well as carbon nanofibers (CNF) are being used for reinforcing polymer matrices. In this study, poly(methyl methacrylate) (PMMA) nanocomposites have been processed by melt blending, containing two different grades (PR-21-PS and PR-24-PS) of CNF manufactured by Applied Sciences Inc. The amount of nanofibers used was 5 and 10% by weight, respectively. The PMMA/CNF composites were processed into 4 mm diameter rods and 60 μm diameter fibers using the small-scale melt processing fiber spinning equipment. At 5 wt% CNF, composite rods as well as fibers show over 50% improvement in axial tensile modulus as compared to the control PMMA rod and fibers, respectively. The reinforcement efficiency decreased at 10 wt% CNFs. The PMMA/CNF nanocomposite fibers also show enhanced thermal stability, significantly reduced shrinkage and enhanced modulus retention with temperature, as well as improved compressive strength. CNF reinforcement efficiency has been analyzed using the modified Cox model.     

Preparation of hydroxyapatite/poly(methyl methacrylate) and calcium silicate/poly(methyl methacrylate) interpenetrating hybrid composites

Hydroxyapatite/poly(methyl methacrylate) (HAp/PMMA) and calcium silicate/poly(methyl methacrylate) (CS/PMMA) composites were prepared by interpenetrating bulk polymerization of methyl methacrylate (MMA) monomer in porous structures of HAp and CS. The porous HAp and CS templates were prepared by mixing their calcined powders with poly(vinyl alcohol) (PVA) solution, shaping by uniaxial pressing and then firing at 1,100 °C for HAp and 900 °C for CS. The templates were soaked in the solution mixture of MMA monomer and 0.1 mol% of benzoyl peroxide (BPO) for 24 h. The pre-composites were then bulk polymerized at 85 °C for 24 h under nitrogen atmosphere. The microstructures of the composites showed the interpenetrating of PMMA into the porous HAp and CS structures. Thermogravimetric analysis indicated that the PMMA content in the HAp/PMMA and CS/PMMA composites were 13 and 26 wt%, respectively. Weight average molecular weights ( ) of PMMA were about 491,000 for HAp/PMMA composites and about 348,000 for CS/PMMA composites. Compressive strengths of these composites were about 90–131 MPa in which they were significantly higher than their starting porous templates.     

Fabrication and characterization of carbon nanotube reinforced poly(methyl methacrylate) nanocomposites

Multiwall carbon nanotube (CNT) reinforced poly(methyl methacrylate) (PMMA) nanocomposites have been successfully fabricated with melt blending. Two melt blending approaches of batch mixing and continuous extrusion have been used and the properties of the derived nanocomposites have been compared. The interaction of PMMA and CNTs, which is crucial to greatly improve the polymer properties, has been physically enhanced by adding a third party of poly(vinylidene fluoride) (PVDF) compatibilizer. It is found that the electrical threshold for both PMMA/CNT and PMMA/PVDF/CNT nanocomposites lies between 0.5 to 1 wt% of CNTs. The thermal and mechanical properties of the nanocomposites increase with CNTs and they are further increased by the addition of PVDF For 5 wt% CNT reinforced PMMA/PVDF/CNT nanocomposite, the onset of decomposition temperature is about 17 degrees C higher and elastic modulus is about 19.5% higher than those of neat PMMA. Rheological study also shows that the CNTs incorporated in the PMMA/PVDF/CNT nanocomposites act as physical cross-linkers.     

Holographic characterization of azo-dye doped poly (methyl methacrylate) films

Many holographic techniques have been developed for non-destructive studies and characterization of materials. In this paper, discussion will be made about the employed holographic technique to characterize the poly(methyl methacrylate) (PMMA) matrices doped with azo-dyes. In this manner we were able to study the effect of the thickness of the samples, the effect of concentration of the azo-dyes and of PMMA and the effect of aging (storage time) on the holographic efficiency (diffraction efficiency) of these materials. Auto-erasable holographic gratings have been successfully recorded on azo-dye doped PMMA films and the dynamic diffraction efficiency was monitored with light different from that used for the recording.     

Optical properties of poly(vinyl chloride)/poly(ethylene oxide) blend

The relatively high dielectric constant poly(vinyl chloride) (PVC) was blended with poly(ethylene oxide) (PEO) polymer electrolytes to improve their electrical conductivity from the optical spectra of the given polymeric system. The optical properties in the UV–visible region of PVC polymer containing 0%, 20%, 50% and 70% by weight PEO are reported. The optical results obtained were analyzed in terms of the absorption formula for non-crystalline materials. The absorption coefficient and the optical band energy gap (E_opt) have been obtained from direct allowed transitions in k-space at room temperature. The width of the tail of localized states in the band gap (ΔE) was evaluated using the Urbach-edges method. It was found that both (E_opt) and (ΔE) vary with the concentration of the PEO complex in the polymer matrix. In addition, a correlation between the energy gap and the ac-conductivity as a function of PEO complex concentration is also reported.     

水包油(O/W)型乳液静电纺丝

将不同质量的聚氧乙烯(PEO)加入到由乳液聚合而得到的均匀的聚甲基丙烯酸甲酯(PMMA)/水乳液中,制备了稳定、质量分数分别为10%、15%、20%的PEO/乳液,并将其作为纺丝液进行静电纺丝。通过纳米粒径分析仪、粘度计、溶液电导率测试仪分析了纺丝液的性质;应用电子显微镜(SEM)分析了纺丝液浓度、纺丝电压、丝液流速对纤维形貌的影响。结果表明,采用乳液静电纺丝法可以制备具有芯-鞘结构的纳米颗粒及纳米纤维。     

Electrospun poly(methyl methacrylate) nanofibers and microparticles

Electrospinning at relatively low polymer concentrations results in particles rather than fibers. This particle-formation process can be termed as electrospray. So electrospinning/electrospray is a highly versatile method to process fibers and particles with different morphologies. In this work, poly(methyl methacrylate) (PMMA) micro- and nanostructures with different morphologies (fibers, spheres, cup-like, and ring-like) have been produced by a facile electrospinning/electrospray method. PMMA was electrospun into various morphologies from only DMF without any other solvents. Field emission scanning electron microscope (FESEM) images demonstrate the different morphologies and prove this technique to be an effective method for obtaining morphology-controllable polymer materials by changing the processing parameters. These micro- and nanostructured polymer materials may find applications in drug delivery and filtration media.     

两嵌段共聚物PMMA-b-PHEMA的合成与表征

采用分步法合成了两嵌段共聚物聚甲基丙烯酸甲酯-b-聚甲基丙烯酸-2-羟乙酯.首先以AIBN为引发剂,FeCl<,3>/PPh<,为>催化体系,通过甲基丙烯酸甲酯(MMA)的反向原子转移自由基聚合,得到端基含Cl的聚合物PMMA-Cl,其分子量分布为1.36;然后以此为大分子引发剂,FeCl<,2>/PPh<,3>为催化...     

Graphite oxide/poly(methyl methacrylate) nanocomposites prepared by a novel method utilizing macroazoinitiator

Graphite oxide (GO)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared by a novel method utilizing macroazoinitiator (MAI). The MAI, which has a poly(ethylene oxide) (PEO) segment, was intercalated between the lamellae of GO to induce the inter-gallery polymerization of methyl methacrylate (MMA) and exfoliate the GO. The morphological, conductivity, thermal, mechanical and rheological properties of these nanocomposites were examined and compared with those of intercalated nanocomposites prepared by polymerization with the normal radical initiator, 2,2′-azobisisobutyronitrile. The improvement in conductivity by GO was more evident in exfoliated nanocomposites compared to that of intercalated nanocomposites. For example, a conductivity of 1.78 × 10⁻⁷ S/cm was attained in the exfoliated nanocomposite prepared with 2.5 parts GO per 100 parts MMA, which was about 50-fold higher than that of the intercalated nanocomposite. The thermal, mechanical and rheological properties also indicate that thin GO with a high aspect ratio is finely dispersed and effectively reinforced the PMMA matrix in both exfoliated and intercalated nanocomposites.     

Double-phase morphology of high molecular weight poly(methyl methacrylate)-epoxy blend

The double-phase morphology of 5 wt% high molecular weight poly(methyl methacrylate) (PMMA) modified epoxy system was investigated by optical and scanning electron microscopic (SEM) techniques. PMMA-epoxy blend cured at 100 °C revealed that a bicontinuous secondary phase separation was observed in both epoxy and PMMA phases in the early stages of curing. Epoxy-rich particles were dispersed in the PMMA-rich phase, while PMMA-rich particles were segregated in the epoxy-rich phase, leading to double-phase bicontinuous morphology. The spinodal decomposition mechanism could probably be responsible for this secondary phase separation. From the SEM analysis, a morphology consisting of a rough striated continuous phase along with large smooth regions was observed. Rough striated domains are ascribed to the PMMA-rich phase and the smooth domains are assigned to the epoxy-rich phase, thus confirming the secondary phase separation. The PMMA-epoxy blend showed a slight increase in flexural properties and about 20% improvement in the fracture toughness.     

Utilization of polymer degradation to modify electrical properties of poly(l-lactide)/poly(methyl methacrylate)/carbon filler composites

This research attempts to utilize polymer degradability in modifying electrical properties of poly(l-lactide) (PLLA)/poly(methyl methacrylate) (PMMA)/carbon fillers composites. Three kinds of carbon particles, i.e. carbon black, vapor-grown carbon fiber, and carbon nanotube, were compounded with PLLA/PMMA blend, followed by hydrolytic degradation of the composites, resulted in degradation of PLLA molecular chain from the surface of samples, with PMMA and carbon particles remained undegraded. By controlling degradation rate, it was possible to prepare samples with low surface resistivity, yet at the same time exhibited high value of volume resistivity. It was also found that final electrical properties of degraded composites depend on the size and the shape of the fillers.     

Temperature dependence of the dielectric permittivity of poly(methyl methacrylate) filled with metal nanoparticles

The temperature dependence of the dielectric constant of composites based on a dielectric poly(methyl methacrylate) (PMMA) matrix containing stabilized nanoparticles of silver has been studied. The Cole-Cole diagrams of PMMA-Ag composites at various temperatures have been constructed and analyzed.     

Processing and properties of poly(methyl methacrylate)/carbon nano fiber composites

Single wall carbon nanotubes, multi-wall carbon nanotubes, as well as carbon nano fibers (CNF) are being used for reinforcing polymer matrices. In this study, poly(methyl methacrylate) (PMMA) nanocomposites have been processed by melt blending, containing two different grades (PR-21-PS and PR-24-PS) of CNF manufactured by Applied Sciences Inc. The amount of nano fibers used was 5 and 10 wt%, respectively. The PMMA/CNF composites were processed into 4 mm diameter rods and 60 μm diameter fibers using small-scale melt spinning equipment. At 5 wt% CNF, composite rods as well as fibers show over 50% improvement in axial tensile modulus as compared to the control PMMA rod and fibers, respectively. The reinforcement efficiency decreased at 10 wt% CNF. The PMMA/CNF nanocomposite fibers also show enhanced thermal stability, significantly reduced shrinkage and enhanced modulus retention with temperature, as well as improved compressive strength. The CNF reinforcement efficiency has been analyzed using the modified Cox model.