Summary: The effect of polymer end group on the morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA) composite particles was investigated on the basis of experimental observations and theoretical predictions. Both polymers with potassium persulfate (KPS)-derived hydrophilic end group(s) and 2,2′-azobis(isobutyronitrile) (AIBN)-derived hydrophobic end group(s) were synthesized by emulsifier-free emulsion polymerizations and solution polymerizations, respectively. Composite particles with the same end groups were prepared by release of toluene from PS/PMMA/toluene (1/1/24, w/w/w) droplets dispersed in an aqueous solution of sodium dodecyl sulfate (SDS). At a low SDS concentration, when the polymers with KPS-derived end group(s) were employed, acornlike particles were formed. On the other hand, when the polymers with AIBN-derived end group(s) were used, particles having a dimple were obtained. The interfacial tensions between toluene solutions of the polymers and SDS aqueous medium were lower for KPS-derived end group(s) than for AIBN-derived end group(s), and the difference was much larger for PS phase than PMMA phase. The predicted morphologies obtained from calculation of the minimum total interfacial free energy using the interfacial tensions agreed well with the experimentally observed morphologies in both cases. Moreover, the morphology of PS/PMMA composite particles with different end groups was also examined. 相似文献
Summary: Polystyrene nanosize particles have been synthesized by a differential microemulsion polymerization process involving the use of a small amount of poly(methyl methacrylate) as the seeds. Sodium dodecyl sulfate and ammonium persulfate were used as the surfactant and initiator, respectively. The effects of various reaction conditions on the particle size have been investigated. Particle sizes of less than 20 nm have been achieved at milder conditions than those previously reported in the literature.
Poly(methyl methacrylate)(PMMA)/polystyrene(PS)/carbon black(CB)and poly(ethyl methacrylate)(PEMA)/PS/CB ternary composite films were obtained using solution casting technique to investigate double percolation effect.In both PMMA/PS/CB and PEMA/PS/CB ternary composite films,the CB particles prefer to locate into PS phase based on the results of calculating wetting coefficient,which is also confirmed by SEM images.The conductivity of the films was investigated,and the percolation threshold(￠c)of both ternary composite films with different polymer blend ratios was determined by fitting the McLachlan GEM equation.Conductivity of PMMA/PS/CB ternary composite films showed a typical double percolation effect.However,due to the double emulsion structure of PEMA/PS polymer blends,the PEMA/PS/CB ternary composite films(PEMA/PS=50/50)showed a higher￠c,even CB only located in PS phase,which conflicts with the double percolation effect.A schematic diagram combined with SEM images was proposed to explain this phenomenon. 相似文献
Multiresponsive polymers that can respond to several external stimuli are promising materials for a manifold of applications. Herein, a facile method for the synthesis of triple-responsive (pH, temperature, CO2) poly(N,N-diethylaminoethyl methacrylamide) by a post-polymerization amidation of poly(methyl methacrylate) (PMMA) is presented. Combined with trivalent counterions ([Fe(CN)6]3−) both an upper and lower critical solution temperature (UCST/LCST)-type phase behavior can be realized at pH 8 and 9. PMMA and PMMA-based block copolymers are readily accessible by living anionic and controlled radical polymerization techniques, which opens access to various responsive polymer architectures based on the developed functionalization method. This method can also be applied on melt-processed bulk PMMA samples to introduce functional, responsive moieties at the PMMA surface. 相似文献
Summary: Submicron core-shell particles of polystyrene (PS) and polystyrene-co-poly(methyl methacrylate) (PS-co-PMMA) coated with PMMA were obtained by emulsion photopolymerization. The seeds of PS or PS-co-PMMA were prepared by emulsion polymerization with or without emulsifier and a ratio of functional monomer and crosslinker (SVBS/EDGMA) in order to obtain different surfaces for the subsequent coating with PMMA. At each stage, the evolution of the average particle size were monitored by using photon correlation spectroscopy (DLS) and the final polymer particles was analyzed via transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The core-shell morphology was identified as the increase of the average particle size in the second stage by DLS technique and by the direct observation by TEM of the differentiation between PS core and PMMA shell, and by the presence of two glass transition temperatures (Tg) as a consequence of the existence of two partially miscible phases. 相似文献
Anisotropic polymer particles such as Janus particles have attracted significant attention in recent years because of their unique properties and unusual self‐assembly behavior. Most anisotropic polymer particles synthesized so far, however, only have different chemical regions compartmentalized on the particles. It remains a great challenge to fabricate anisotropic polymer particles with different shapes within a single particle. A novel approach is developed to prepare anisotropic polymer particles that contain two hemispheres with different curvatures by annealing polystyrene microspheres on poly(vinyl alcohol) films. During the annealing process, the polymer microspheres gradually sink into the polymer films and transform to asymmetric polymer particles, driven by the surface and interfacial tensions of the polymers. Selective removal techniques are also used to confirm the morphologies of the asymmetric particles.
The effect of di-tert-butylhydroxylamine on polymerization of methyl methacrylate and styrene under conditions of radical initiation, similar to the commercial synthesis conditions, was studied. 相似文献
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 Tg∞ of PiBuMA (331 K) agrees well with the literature value (326 K), Tg∞ of atactic PMMA (394 K) is higher than the reported value (378 K). 相似文献
The stereoregularity of poly(methyl methacrylate) obtained with complex bases in various solvents was determined by 1H-NMR spectroscopy. Polymethyl methacrylates produced by complex bases are mostly hetero and/or syndiotactic and obey Bernoullian statistics. 相似文献
The uniformity, light fastness, heat resistance, radiation hardness, and antistatic properties of poly(methylmethacrylate) prepared in the presence of metal sulfoxide complexes were studied. 相似文献
A novel water insoluble, multifunctional poly(ethylene glycol), poly(hydrazide ethylene glycol‐co‐benzyl glycidyl ether) (P(HZ‐co‐BnGE)), is synthesized via thiol‐ene click reaction of poly(allyl glycidyl ether‐co‐benzyl glycidyl ether) (P(AGE‐co‐BnGE)). The base polymer P(AGE‐co‐BnGE) is previously prepared by anionic ring‐opening copolymerization of the corresponding monomers. To demonstrate utility, bicompartmental microspheres and microcylinders containing P(HZ‐co‐BnGE) in one of the compartments are prepared via electrohydrodynamic (EHD) co‐jetting. Next, spatially controlled surface reactivity toward sugars is demonstrated by selective binding of 2α‐mannobiose to the P(HZ‐co‐BnGE) compartment only, as confirmed by a carbohydrate‐lectin‐binding assay. These sugar‐reactive hydrazide‐presenting microparticles have potential applications for glyco‐targeted drug delivery.
