Absorption and photoluminescence of Buriti oil/polystyrene and Buriti oil/poly(methyl methacrylate) blends

This work reports the preparation and characterization of Buriti (Mauritia flexuosa L.) oil/polystyrene (PS) and Buriti oil/poly(methyl methacrylate) blends. The Buriti is an abundant palm tree of the Amazon region. This oil was used because of its chemical composition (high concentrations of oleic acid, tocopherols and carotenoids, especially β-carotene) and interesting optical properties, such as absorption and photoluminescence. The incorporation of the vegetable oil in the PS and PMMA matrices renders orange-colored blends, which were verified to absorb UV-Vis radiation and emit light in the green region. The intensity of these properties is proportional to the oil content in the samples. Micrographs of the blends showed that the oil is located in cavities distributed in the polymeric matrices. This work shows that it is possible to employ the Buriti oil, a cheaper and abundant natural resource, to improve absorption and light emission properties of PS and PMMA polymers.     

Preparation and characterization of microporous PVDF/PMMA composite membranes by phase inversion in water/DMSO solutions

PMMA/PVDF composite membranes were prepared by isothermal immersion-precipitation of dope solutions consisting of PMMA, PVDF, and DMSO into both harsh and soft nonsolvent baths. The effects of PMMA and DMSO contents on the membrane morphology, crystal structure, thermal behavior and tensile strength of the formed membrane were investigated. For a PMMA-free casting dope immersed in a harsh bath, such as pure water, the formed membrane exhibited a typical asymmetric morphology characterized by skin, finger-like macrovoids, and cellular pores. In contrast, when a soft 70% DMSO bath was adopted, PVDF crystallized to form a membrane packed by spherulitic globules. Incorporation of PMMA gave rise to interesting morphological features; e.g., PVDF globules were observed to adhere to the interlocked polymer branches coexisting with the continuous porous channels, as revealed by high resolution FESEM imaging. XPS analysis of the surfaces of the composite membranes suggested the occurrence of a surface segregation phenomenon, wherein PVDF preferentially migrated to the top surface region of the membrane such as to minimize the interfacial energy. XRD analyses indicated that PVDF crystallized into ‘α’ structure in both PVDF and PMMA/PVDF composite membranes. The crystallinity of the membranes was found to decrease with increasing PMMA content, which was confirmed by DSC thermal analyses. The latter results also indicated a significant decrease in membrane’s melting temperature as the PMMA content was increased. Tensile strengths of the membranes were improved by inclusion of PMMA in either harsh or soft baths. However, elongation at break showed a reversed trend.     

Poly(methyl methacrylate)-induced Microstructure and Hydrolysis Behavior Changes of Poly(L-lactic acid)/Carbon Nanotubes Composites

Poly(L-lactic acid)(PLLA)-based composites exhibit wide applications in many fields.However,most of hydrophilic fillers usually accelerate the hydrolytic degradation of PLLA,which is unfavorable for the prolonging of the service life of the articles.In this work,a small quantity of poly(methyl methacrylate)(PMMA)(2 wt%-10 wt%)was incorporated into the PLLA/carbon nanotubes(CNTs)composites.The effects of PMMA content on the dispersion of CNTs as well as the microstructure and hydrolytic degradation behaviors of the composites were systematically investigated.The results showed that PMMA promoted the dispersion of CNTs in the composites.Amorphous PLLA was obtained in all the composites.Largely enhanced hydrolytic degradation resistance was achieved by incorporating PMMA,especially at relatively high PMMA content.Incorporating 10 wt%PMMA led to a dramatic decrease in the hydrolytic degradation rate from 0.19%/h of the PLLA/CNT composite sample to 0.059%/h of the PLLA/PMMA-10/CNT composite sample.The microstructure evolution of the composites was also detected,and the results showed that no crystallization occurred in the PLLA matrix.Further results based on the interfacial tension calculation showed that the enhanced hydrolytic degradation resistance of the PLLA matrix was mainly attributed to the relatively strong interfacial affinity between PMMA and CNTs,which prevented the occurrence of hydrolytic degradation at the interface between PLLA and CNTs.This work provides an alternative method for tailoring the hydrolytic degradation ability of the PLLA-based composites.     

Effect of inorganic phase on polymeric relaxation dynamics in PMMA/silica hybrids studied by dielectric analysis

Dielectric relaxation spectroscopy was used to investigate the effect of the inorganic phase on the polymeric relaxation dynamics in PMMA/silica hybrids synthesized in situ via sol-gel processes. It was found that the large-scale molecular motions of PMMA were influenced by the addition of silica, inducing longer mean relaxation times, more heterogeneous relaxing environments and the higher activation energy. Explanations based on hydrogen-bond interactions between two phases and a fraction of entrapped chain segments in silica networks were proposed to understand the influence of the silica.     

Click chemistry meets polymerization: Controlled incorporation of an easily accessible ruthenium(II) complex into a PMMA backbone via RAFT copolymerization

The copper(I)-catalyzed azide-alkyne cycloaddition provided an easy and efficient access to a functionalized heteroleptic ruthenium(II) complex monomer. A grafted copolymer with the heteroleptic ruthenium(II) complex and methyl methacrylate (MMA) as comonomer was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. The product was characterized by means of ¹H NMR spectroscopy, UV/vis spectroscopy and size exclusion chromatography coupled with a photodiode array detector. The RAFT process itself led to a grafted copolymer with a low polydispersity index.     

聚甲基丙烯酸甲酯微流控芯片分离DNA片段的初步研究

自从1995年Mathies^[1]首次将微流控芯片毛细管凝胶电泳用于基因测序研究以来,DNA片段的分离已成为微流控芯片应用的重要领域之一.最早应用于DNA分析的微流控芯片是玻璃芯片,聚合物微流控芯片以其品种多、成本低、易于加工,与玻璃芯片相比具有封接温度大大降低,微通道内电渗流显著减小等特点,已被成功应用于DNA片段的分离^[2,3].     

The role of the trivalent metal in an LDH: Synthesis, characterization and fire properties of thermally stable PMMA/LDH systems

Two layered double hydroxides (LDHs), calcium aluminum undecenoate (Ca₃Al) and calcium iron undecenoate (Ca₃Fe), have been prepared by the co-precipitation method. XRD analysis of these LDHs reveals that they are layered materials and FT-IR and TGA confirmed the presence of the undecenoate anions in the material produced. The PMMA composites were prepared by bulk polymerization and the samples were characterized by XRD, TEM, TGA and cone calorimetry. Both additives greatly enhance the thermal stability of PMMA, while the calcium aluminum LDH gives better results when the fire properties were examined using the cone calorimeter.     

A novel method for encapsulation of a liquid crystal in monodisperse micron-sized polymer particles

Liquid crystals (LCs) encapsulated in monodisperse micron-sized polymer particles were prepared to control the size and size distribution of LC droplets in polymer-dispersed LCs. The poly(methyl methacrylate) (PMMA) seed particles were swollen with the mixture of liquid crystal, monomers (methyl methacrylate and styrene) and initiator by using a diffusion-controlled swelling method. A single LC domain was produced by the phase separation between PMMA and LC through polymerization. The optical microscopy and scanning electron microscopy showed that the particles are highly monodisperse with core–shell structure. Moreover, monodisperse LC core domains were confirmed from polarized optical microscope observations. The final particle morphology was influenced by the cross-linking of the seed particle. When linear PMMA particles, which are not cross-linked, were used as a seed, the microcapsules were distorted after annealing for a few days; however, in the case of cross-linked PMMA particles, the core–shell structure was sustained stably after annealing. Received: 22 November 2000 Accepted: 12 March 2001     

Radiation degradation of poly(methyl methacrylate) in the soft x-ray region

The molecular weight distribution change has been measured for the photoresist poly(methyl methacrylate) [PMMA] after in-vacuo exposure to monochromatic soft x-rays from the Canadian Synchrotron Radiation Facility [CSRF]. The experimental changes in the mo-lecular weight distribations derived from gel permeation chromatography [GPC], were compared to a simple Monte Carlo simulation model that assumes random main chain scission. Using this model a scission radiation chemical yield of G(S) = 1.28± 0.10 at room temperature was found to give the best fit at a photon energy of 621 eV. This value is similar to values reported previously in the literature using electron beam and γ-ray sources, but significantly larger than those reported for fast neutrons, α-particles, or energetically charged particles. It was found that in this soft x-ray energy regime, that degradation of PMMA involves primarily a random scission process of the main chain. The results of a least-squares fit of this soft x-ray G(S) data and all available literature values from other radiation sources, to the linear energy transfer [LET] dE/dx are discussed. © 1993 John Wiley & Sons, Inc.     

Studies on Poly(Methyl Methacrylate) (PMMA) and Thermoplastic Polyurethane (TPU) Blends

Blends of poly(methyl methacrylate) (PMMA) and thermoplastic polyurethane (TPU) in different compositions viz., 95/5, 90/10, 85/15 and 80/20 (by wt/wt, % of PMMA/TPU) were blended by melt mixing using a twin‐screw extruder. All the PMMA/TPU blends have been characterized for physico‐mechanical properties such as density, melt flow index, tensile behavior and izod impact strength. The impact strength of the PMMA/TPU blends were found to increase significantly with an increase in the percentage of TPU up to 20%, by retaining the tensile strength of PMMA. The effect of chemical aging on the performance of blends has been studied.     

Light scattering studies of stereocomplex formation of stereoregular poly(methyl methacrylate) in solutions

The structure and stereocomplex formation of multi-stereoblock poly(methyl methacrylates) in three different solvents, acetone, tetrahydrofuran (THF) and chloroform, corresponding to strongly-, weakly- and non-complexing solvent, respectively, were investigated by a combination of static and dynamic laser light scattering. Our results revealed that the stereocomplex was caused by weak interactions, and could be melted at higher temperatures. In THF, the intermolecular and intramolecular interactions could be clearly separated at lower temperatures, and the structure of aggregated chains was linear. In acetone, a more compact structure was obtained, which was corroborated by the fact that the stereocomplex had a higher melting temperature than in THF.     

Ricinus communis agglutinin I functionalisation of poly(methyl methacrylate) (PMMA) as a substrate for microfluidic device

We report a functionalisation strategy which is able to generate Ricinus communis agglutinin I (RCA 120) modified PMMA microfluidic device for binding and culturing living cells. The functionalisation is achieved by standard amine-aldehyde (Schiff base) reaction through the cross-linker, glutaraldehyde. To prove the ability of the RCA 120 modified PMMA surface, the PC 12 cell line (rat pheochromocytoma cells) has been captured and cultured by the microfluidic device. In the presence of tunicamycin, the dose/time-dependence on decreasing of binding affinity of RCA 120 modified device with PC 12 cell is also observed. The experimental results demonstrate that the lectin-functionalized microfluidic device can be employed as efficient cell culturing platform, and has a great promise of being used as a powerful tool for monitoring the interaction of drug with living cell.     

Chemical recycling of poly(methyl methacrylate) by pyrolysis. Potential use of the liquid fraction as a raw material for the reproduction of the polymer

Pyrolysis of poly(methyl methacrylate) (PMMA) was studied as an effective way to recycle this polymer and recover its monomer methyl methacrylate (MMA). Experiments were carried out in a laboratory fixed bed reactor using either a model polymer or a commercial product based on PMMA as feedstock. Gaseous and liquid products obtained from polymer degradation were analysed and it was found that the oil fraction constituted mainly of the MMA monomer. Thus, the possibility of directly using the liquid product for the reproduction of the polymer was further investigated. Polymerizations accomplished in a differential scanning calorimeter using azo-bis-isobutyronitrile as initiator and different reaction temperatures. Results obtained were compared to corresponding data from polymerization of neat monomer. It was found that the pyrolysis liquid fraction can be polymerized and produce a polymer similar to the original PMMA. However, even small amounts of other organic compounds (mainly methyl esters) included in this fraction act as non-ideal reaction retarders, altering the reaction rate curve and lowering the glass transition temperature and the average molecular weight of the polymer produced.     

Synthesis of nano-ZnO/poly(methyl methacrylate) composite microsphere through emulsion polymerization and its UV-shielding property

Nano-ZnO/poly(methyl methacrylate)(PMMA) composite latex microspheres were synthesized by in-site emulsion polymerization. The interfacial compatibility between nano-ZnO particles and PMMA were improved by treating the surface of nano-ZnO particles hydrophobically using methacryloxypropyltrimethoxysilane (MPTMS). TEM indicated that nano-ZnO particles present in nanosphere and have been encapsulated in the PMMA phase. FT-IR confirmed that MPTMS reacted with the nano-ZnO particle and copolymerized with MMA. It was clearly found from SEM that ZnO nanoparticles can be homogeneously dispersed in the PVC matrix. The absorbance spectrum of the nanocomposite polymer suggested that increasing the amount of nano-ZnO in composite particles could enhance the UV-shielding properties of the polymers. The nano-ZnO/PMMA composite particle could eliminate aggregation of ZnO nanoparticle and improve its compatibility with organic polymer. This means that the composite particles can be widely applied in lots of fields.     

Methyl methacrylate in poly(methyl methacrylate)--validation of direct injection gas chromatography

Gas chromatography (GC) was investigated for the determination of residual methyl methacrylate (MMA) in heat-processed poly(methyl methacrylate) (PMMA) denture base material emphasizing recovery and validation. Standard solutions of MMA and emulsion-polymerized PMMA in dichloromethane were analysed, before and after distillation by a room-temperature air stream into a liquid nitrogen trap, and in the presence of PMMA by direct injection. Quantitative NMR analysis using dimethyl sulphoxide as internal calibration standard in deuterated chloroform solutions provided validation. Good concordance was observed between results under all conditions; no problems arose from direct injection of PMMA solution for GC. Good straight line responses in log-log plots were generally observed. For GC and MMA: log-log calibration curve (slope: 0.9552 +/- 0.0051, r2: 0.9992, n = 32) indicated some non-linearity (t = 8.875, p approximately 4 x 10(-10)). Distillation gave slope: 0.9751 +/- 0.0213 (NS versus unity; t = 1.172, p > 0.25). For PMMA solutions, distillation (r2: 0.9301) gave greater scatter than direct injection (r2: 0.9704). For NMR: log-log plot of calculated versus actual MMA (slope: 0.9363 +/- 0.0157, r2: 0.9969, n = 13) again indicated non-linearity (t = 4.0682, p = 0.0019). PMMA solutions gave slope: 0.9477 +/- 0.0328, r2 = 0.9858 (NS versus unity; t = 1.5941, p = 0.13). Determination of MMA in PMMA by GC is recommended.     

Preparation of poly(methyl methacrylate) microcapsules by in situ polymerization on the surface of calcium carbonate particles

Poly(methyl methacrylate) (PMMA) microcapsules were prepared by the in situ polymerization of methyl methacrylate (MMA) and N,N′-methylenebisacrylamide on the surface of calcium carbonate (CaCO₃) particles, followed by the dissolution of the CaCO₃ core in ethylenediaminetetraacetic acid solution. The microcapsules were characterized using fluorescence microscopy, atomic force microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy. The average sizes of the CaCO₃ particles and PMMA capsules were 3.8 ± 0.6 and 4.0 ± 0.6 μm, respectively. A copolymer consisting of MMA and rhodamine B-bearing MMA was also used to prepare microcapsules for fluorescent microscopy observations. Fluorescein isothiocyanate-labeled bovine serum albumin was enclosed in the PMMA microcapsules and its release properties were studied.     

Twisted nematic LC mode with high electro-optical performance and high thermal endurance formed using IB-irradiated poly(methyl methacrylate) as an alignment layer

We obtained homogeneously aligned liquid crystals (LCs) on ion beam (IB) irradiated poly(methyl methacrylate) (PMMA) by controlling the IB energy. We then examined the LC alignment state using polarized optical microscopy and conducted thermal stability testing. We obtained homogeneous LC alignment at IB energies above 1,400 eV, indicating that strong IB energy facilitates the alignment of LCs on the PMMA surface. This surface was analyzed by atomic force microscopy, and the contact angles (CAs) were measured to elucidate the mechanism of LC alignment. The increased surface energy strengthened the van der Waals interaction between the surface and LCs, thereby inducing stable, homogeneous LC alignment. Electro-optical (EO) characteristics were measured using twisted nematic (TN) LC mode. Compared to LC cells with conventionally used rubbed polyimide (PI), the LC cells with IB-irradiated PMMA exhibited higher thermal budgets and good electro-optical characteristics. These new LC cells have promising potential for advanced LC displays.     

Structural characterization of a poly(methacrylic acid)-poly(methyl methacrylate) copolymer by nuclear magnetic resonance and mass spectrometry

Mass spectrometry (MS) and nuclear magnetic resonance (NMR) have been combined to achieve the complete microstructural characterization of a poly(methacrylic acid)-poly(methyl methacrylate) (PMAA-PMMA) copolymer synthesized by nitroxide-mediated polymerization. Various PMAA-PMMA species could be identified which mainly differ in terms of terminaisons. ¹H and ¹³C NMR experiments revealed the structure of the end-groups as well as the proportion of each co-monomer in the copolymers. These end-group masses were further confirmed from m/z values of doubly charged copolymer anions detected in the single stage mass spectrum. In contrast, copolymer composition derived from MS data was not consistent with NMR results, obviously due to strong mass bias well known to occur during electrospray ionization of these polymeric species. Tandem mass spectrometry could reveal the random nature of the copolymer based on typical dissociation reactions, i.e., water elimination occurred from any two contiguous MAA units while MAA-MMA pairs gave rise to the loss of a methanol molecule. Polymer backbone cleavages were also observed to occur and gave low abundance fragment ions which allowed the structure of the initiating end-group to be confirmed.     

聚甲基丙烯酸甲酯与苯乙烯-丙烯腈共聚物混合体系相分离初期的固体NMR研究

本文用氢谱宽线固体NMR技术研究了聚甲基丙烯酸甲酯(PMMA)和苯乙烯-丙烯腈共聚物(SAN)混合体系不稳相分离初期阶段, 得到了在分相过程中弛豫谱的变化规律, 测定了相分离增长速率。结果指出: 随着退火时间的增加, 两相体系形成; 大分子扩散方式是由浓度低的区域向浓度高的区域扩散, 扩散系数为负值; 相分离增长速率的数量级与用光散射研究的结果相同; 分子相互作用的相关距离为46.5 nm。     

Crystallization behavior and hydrophilicity of poly(vinylidene fluoride) (PVDF)/poly(methylmethacrylate) (PMMA)/poly(styrene-<Emphasis Type="Italic">co</Emphasis>-acrylonitrile) (SAN) ternary blends

Compatibilization of the partially miscible poly(vinylidene fluoride) (PVDF)/poly(styrene-co-acrylonitrile) (SAN) pair by a third homopolymer, i.e., poly(methyl methacrylate) (PMMA), was investigated in relation to cross section morphology, crystallization behaviors and hydrophilicity of the polyblends. Scanning electron microscopy showed a more regular and homogeneous morphology when more than 15 wt.% PMMA was incorporated. The samples presented only α phase regardless of PMMA content in the blend. As the PMMA content increased in the blends, the interactions between each component were enhanced, and the crystallization of PVDF was limited, leading to a decreasing of the crystallinity and the crystallite thickness. Besides, the hydrophilicity of PVDF was further improved by PMMA addition. The sample containing 15 wt.% PMMA showed a more hydrophilic property due to the more polar part of surface tension induced by PMMA addition. Observed from the cross section of the blends, the miscibility of partially miscible PVDF/SAN blends were efficiently improved by PMMA incorporation.