Compatibility of binary systems of poly(methyl methacrylate), poly(vinyl chloride) and poly(vinyl acetate)

The influence of the thermal treatment on the stability in time of the dispersion degree of films containing binary polymer mixtures, poly(vinyl chloride)/poly(methyl methacrylate), poly(vinyl chloride)/poly(vinyl acetate) and poly(vinyl acetate)/poly(methyl methacrylate), was studied by thermogravimetry and optical microscopy with phase contrast. The dispersion degree depends particularly on the composition of the polymer mixture and can be improved by thermal treatment at temperatures above the glass temperatures of both homopolymers. It seems that this thermal treatment yields exclusively metastable structures with a general tendency to phase separation in a short time after thermal treatment, the heterogeneity mixtures (as film) being more pronounced.     

Connection of poly(methyl methacrylate) microgel particles dispersed in poly(vinyl alcohol) matrix by seed polymerization

Poly(methyl methacrylate) microgels covered with poly(hydroxyethyl methacrylate) thin layer was dispersed in poly(vinyl alcohol) matrix. Homogeneous and regular arrangement of the microgel particles was suggested by Bragg diffraction for the films prepared by varying the PVA/microgel ratio (from 6/4 to 3/7 (w/w)). It was proved that the regular arrangement and connection of the microgels by seeded polymerization in poly(vinyl alcohol) were possible. © 1996 John Wiley & Sons, Inc.     

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.     

Reaction of aluminium chloride with poly(divinyl benzene) particles--a reaction kinetic study using infrared spectroscopy

Porous poly(para-divinylbenzene) and poly(meta-divinylbenzene) particles were synthesised from para-divinylbenzene and meta-divinylbenzene monomers with toluene and 2-ethylhexanoic acid as porogens. The residual vinyl groups in the particles were thereafter reacted using aluminium chloride with dichlorobenzene as a catalyst. The conversion of vinyl groups was followed by analysing polymer particles taken from the reaction mixture at different time intervals. Infrared spectroscopy both in the mid and near infrared region was used as the analytical technique. The intensity changes in the overtone absorption at 1628 nm due to the vinyl bonds were used as the basis for the quantification of the vinyl group consumption. Infrared spectra of the particles in the mid IR were also measured to understand changes taking place in the polymer matrix during the reaction. The results indicated that residual vinyl groups in these polymer particles were consumed during the reaction with aluminium chloride. The reaction of aluminium chloride with the polymer matrix was explained by proposing mechanisms for the formation of different products during the reaction. The complex formed between aluminium chloride and the residual vinyl groups seemed to induce addition of HCl to the vinyl group or leads to crosslinking and/or cyclisation in the case poly(para-DVB) particles. The reaction of aluminium chloride with poly(meta-DVB) takes place to a lesser extent.     

The estimation of phase modifications in polymers by the method of “molecular probes” in gas chromatography—III. Glass transition behaviour and compatibility in mixtures of poly(methyl methacrylate) with poly(vinyl chloride)

Using the method of “molecular probes” in gas chromatography, glass-transitions in mixtures of poly(methyl methacrylate) with poly(vinyl chloride) are found. The strong variation of T_g for poly (methyl methacrylate) in mixtures with more than 20% of that polymer suggests interactions although T_g for poly(vinyl chloride) remains constant. The existence of a single T_g in mixtures with less than 20% poly(methyl methacrylate), on the other hand, suggests possible compatibility in these mixtures.     

THE COMPATIBILITY OF BLENDS OF POLY(VINYL CHLORIDE) OR CHLORINATED POLY(VINYL CHLORIDE) WITH POLY(METHYL METHACRYLATE)

IR spectral shifts of carbonyl vibrational absorption for ethyl acetate, which acts analogically as the structural unit of poly(methyl methacrylate), in cyclohexane, chloroform, chlorinated paraffins, poly(vinyl chloride) and chlorinated poly(vinyl chloride) were measured. The results suggest that there are specific interactions between the carbonyl groups and the chlorinated hydrocarbons which could be responsible for the apparent compatibility of poly(vinyl chloride)—poly(methyl methacrylate) and chlorinated poly(vinyl chloride)—poly(methyl methacrylate) blends. Additionally, the effects of the preparation mode of blend films on phase separation and observed compatibility are discussed.     

The morphology of composite polymer particles produced by multistage soapless seeded emulsion polymerization

 Composite polymer particles which contain poly(methyl methacrylate) (PMMA) and polystyrene (PS) components (PMMA/PS composite particle) were synthesized by the method of multistage soapless seeded emulsion polymerization. In this study, the process of multistage soapless seeded emulsion polymerization included two-stage polymerization, three-stage polymerization or four-stage polymerization. The morphologies of the PMMA/PS composite particles were studied. The kinetic factor was the main force to control the morphology of the linear PMMA–PS composite particles which were synthesized by the method of two-stage reaction. Both the kinetic factor and the thermodynamic factor decide the morphology of the linear composite particles which were synthesized by the method of either three-stage or four-stage reaction. However, the thermodynamic factor cannot influence the morphology of the PMMA/PS composite particles with a cross-linked structure which were synthesized by the method of three-stage reaction. The cross-linked composite polymer particles had the morphology of a multilayer structure, which showed that the polymer layers accumulated in their order of production. Received: 9 January 2001 Accepted: 14 June 2001     

The role of initiation in the synthesis of silica/poly(methyl methacrylate) nanocomposite latex particles through emulsion polymerization

Silica/poly(methyl methacrylate) nanocomposite latex particles have been synthesized by emulsion polymerization of methyl methacrylate using a nonionic surfactant: nonylphenol poly(oxyethylene) and three different initiators, namely: 2,2′-azobis(2-amidinopropane) dihydrochloride (AIBA), potassium persulfate (KPS) and azobis(isobutyronitrile) (AIBN), being cationic, anionic and nonionic, respectively. A silica sol with an average diameter of 68 nm was used as the seed. The polymerization reaction was conducted under alkaline conditions in order to evaluate the role of the surface charge of the hydrophilic silica on the coating reaction. AIBA was found to be adsorbed on the silica surface owing to electrostatic interactions of the amidine function of the cationic initiator with the silanolate groups of the oxide surface, while the anionic and the nonionic initiators did not adsorb on silica under the same conditions. Nonetheless, whatever the nature of the initiator, polymerization took place on the silica particles as evidenced by transmission electron microscopy. The extent of interaction between the inorganic surface and the polymer particles was quantified by means of ultracentrifugation and a material balance. As much as 65% by weight of the total polymer formed was found to be present at the silica surface using AIBA, while only 40% for KPS and 25% for AIBN was found to cover the silica particles under alkaline conditions. We demonstrate that by using a cationic initiator and by controlling the pH of the suspension it is possible to significantly decrease the amount of free polymer. Coating of the silica particles took place through a kind of in situ heterocoagulation mechanism. Received: 8 December 2000 Accepted: 22 February 2001     

Friedel–crafts reactions of pendant vinyl groups in macroporous monosized poly(meta‐divinylbenzene) and poly(para‐divinylbenzene) particles

Residual vinyl groups in macroporous monosized polymer particles of poly(meta‐DVB) and poly(para‐DVB) prepared with toluene and 2‐EHA as porogens have been reacted with aluminum chloride as Friedel–Crafts catalyst with and without the presence of lauroyl chloride. In the reaction between aluminum chloride and pendant vinyl groups a post‐crosslinking by cationic polymerization takes place. A reaction occurring simultaneously is the addition of HCl to the double bonds. The progress of these reactions was studied by characterization of vinyl group conversion, pore size distribution, specific surface area, morphology, and swelling behavior. In the reaction with aluminum chloride the poly(para‐DVB) particles showed a substantially higher conversion of pendant vinyl groups than the particles made of poly(meta‐DVB) independent of porogen type. The reaction with aluminum chloride led to a reduced swelling in organic solvents and an increased rigidity of the particles prepared with toluene as porogen. This is confirmed by an increase in the total pore volume in the dry state and a change in the pore size distribution of these particles. Also in the reaction with lauroyl chloride poly(para‐DVB) particles have shown a higher conversion of pendant vinyl groups than poly(meta‐DVB) particles and the acylation was almost complete at the early stage of the reaction. The swelling in organic solvents is reduced as a result of the incorporation of acyl groups into the particles prepared with toluene as porogen. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1366–1378, 2000     

Preparation and application of cross-linked core-shell PBA/PS and PBA/PMMA nanoparticles

This paper reports the preparation of cross-linked core-shell poly(butyl acrylate)/polystyrene (PBA/PS) and poly(butyl acrylate)/poly(methyl methacrylate) (PBA/PMMA) nanoparticles via seeded emulsion polymerization and their application in nylon-based composites. A highly cross-linked structure was formed in both the cores and the shells by using a cross-linking agent, which could prevent the migration of hydrophobic PS shells to the inside of particles. There were covalent bonds on the interfaces between the cores and the shells of both particles. The average particle sizes were 40–50 nm, and the size distributions were narrow. The kinetics of polymerization was investigated. Well-defined core-shell structure and narrow particle size distribution could be achieved under starved conditions of monomer feeding. Furthermore, PBA/PMMA particles were used to fill nylon 6, good dispersion was obtained because of the strong interfacial interaction between the nanoparticles and the nylon 6 matrix and the good deformation ability of nanoparticles, and the toughness and rigidity of the composites were improved evidently. __________ Translated from Acta Polymerica Sinica, 2005, (6) (in Chinese)     

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     

Preparation of micron-size monodisperse poly(2-hydroxyethyl methacrylate) particles by dispersion polymerization

Dispersion polymerization of 2-hydroxyethyl methacrylate using four categories of polymeric stabilizers in a mixture of good and poor solvents was performed to produce polymeric particles. The stabilizers employed were methyl methacrylate and styrene homopolymers, methacryloyl-terminated poly(methyl methacrylate) and polystyrene macromonomers, an amphiphilic poly(methyl methacrylate-co-methacrylic acid-graft-styrene), and polybutadiene derivatives containing reactive vinyl groups. Dispersion copolymerization with a small amount of the macromonomer gave micron-size particles with relatively narrow size distribution. The amphiphilic graft copolymer and the polybutadiene derivatives also afforded monodisperse particles. The mixed ratio between good and poor solvents greatly affected the particle size and size distribution. © 1996 John Wiley & Sons, Inc.     

Thermal and electrochemical characteristics of plasticized polymer electrolytes based on poly(acrylonitrile-co-methyl methacrylate)

The thermal and electrochemical characteristics of plasticized polymer electrolytes composed of poly(acrylonitrile-co-methyl methacrylate) [P(AN-co-MMA)], a plasticizer [a mixture of ethylene carbonate and propylene carbonate], and LiCF₃SO₃ were investigated. The incorporation of a MMA unit into the matrix polymer was effective for an increase in the compatibility between the matrix polymer and the plasticizer. The comparative investigation of the interfacial resistance of the Li/polymer electrolyte/Li cell for the PAN-based and the P(AN-co-MMA)-based polymer electrolytes showed that the MMA unit could improve the stability of the polymer electrolyte toward the Li electrode, which is probably due to the enhanced adhesion of the polymer electrolyte to the Li electrode. Received: 14 July 1997 / Accepted: 14 May 1998     

Synthesis of cross-linked poly(methyl methacrylate) via dispersion polymerization in supercritical carbon dioxide

Cross-linked poly(methyl methacrylate) particles were prepared via dispersion polymerization in supercritical carbon dioxide (scCO₂) using poly(heptadecafluorodecyl methacrylate) (PHDFDMA) and 2,2′-azobisisobutyronitrile as the dispersant and the initiator, respectively. The following chemicals were used as cross-linking agents: ethylene glycol dimethacrylate (EGDMA), 1,4-buthanediol di(meth)acrylate (1,4-BD(M)A), and trimethylolpropane trimethacrylate. PHDFDMA was synthesized by solution polymerization in scCO₂. We investigated the effect of the chemical structure, concentration of the cross-linking agents, reaction pressure, and CO₂ density on the morphology, the polydispersity, and the cross-linking density of polymer particles. The resulting polymer particle was characterized by field emission SEM, differential scanning calorimetry, and thermal gravimetric analysis. The cross-linked PMMA particles is more agglomerate as the cross-linking agent concentration increased and as pressure decreased at constant temperature. Glass-transition temperature (T _g) of the resulting polymer increased as the cross-linking agent increased with temperature and pressure increasing at the same CO₂ density. Decomposition temperature is slightly increased as 1,4-BDA concentration increased. From these results, we can confirm that the thermal stability of the polymer increased as the cross-linking agent and EGDMA is the best cross-linking agent in term of the thermal stability.     

The influence of core-shell structured modifiers on the toughness of poly (vinyl chloride)

The core-shell structured grafted copolymer particles of polybutadiene grafted polymethyl methacrylate (PB-g-PMMA, MB) were prepared by emulsion polymerization. The MB particles were used to modify poly (vinyl chloride) (PVC) by melt blending. The mechanical properties of the PVC blends were investigated. The micro-morphology of the PVC blends was observed by scanning electron microscopy (SEM). The results indicated that the samples with the best impact strength could be obtained when the core-shell weight ratio of PB to PMMA is lower than 93:7, the mechanical properties correlated well with SEM morphologies, the addition of modifier with the ratio core to shell of 93:7 could reduce the domain size of the dispersed phase. Furthermore, the compatibility and properties of the blends were greatly enhanced and improved. The modifier particles could be well dispersed in the PVC matrix.     

Preparation of poly(4-butyltriphenylamine) particles by chemical oxidative dispersion polymerization

Photoconductive poly(4-butyltriphenylamine) particles were prepared by a chemical oxidative dispersion polymerization. The utilization of statistical copolymer of methyl methacrylate with 2-hydroxyethyl methacrylate (30:70) as a dispersant afforded particles with the narrowest distribution when the other experimental conditions such as the rate of monomer feed, and the dispersant concentration were appropriately selected. Porous particles were obtained at 40 °C using poly(vinyl pyrrolidone) as a dispersant.     

Persistent interactions between hydroxylated nanoballs and atactic poly(2-hydroxyethyl methacrylate)(PHEMA)

The incorporation of self-assembled nanoparticles, a.k.a. hydroxylated nanoballs, into poly(2-hydroxyethyl methacrylate)(PHEMA) gives rise to a cross-linked network/hydrogel with enhanced interfacial interaction, whereas its inclusion in poly(methyl methacrylate)(PMMA) results in plasticization.     

Effects of organoclays on morphology and thermal and rheological properties of polystyrene and poly(methyl methacrylate) blends

Morphology, thermal and rheological properties of polymer‐organoclay composites prepared by melt‐blending of polystyrene (PS), poly(methyl methacrylate) (PMMA), and PS/PMMA blends with Cloisite® organoclays were examined by transmission electron microscopy, small‐angle X‐ray scattering, secondary ion mass spectroscopy, differential scanning calorimetry, and rheological techniques. Organoclay particles were finely dispersed and predominantly delaminated in PMMA‐clay composites, whereas organoclays formed micrometer‐sized aggregates in PS‐clay composites. In PS/PMMA blends, the majority of clay particles was concentrated in the PMMA phase and in the interfacial region between PS and PMMA. Although incompatible PS/PMMA blends remained phase‐separated after being melt‐blended with organoclays, the addition of organoclays resulted in a drastic reduction in the average microdomain sizes (from 1–1.5 μm to ca. 300–500 nm), indicating that organoclays partially compatibilized the immiscible PS/PMMA blends. The effect of surfactant (di‐methyl di‐octadecyl‐ammonia chloride), used in the preparation of organoclays, on the PS/PMMA miscibility was also investigated. The free surfactant was more compatible with PMMA than with PS; the surfactant was concentrated in PMMA and in the interfacial region of the blends. The microdomain size reduction resulting from the addition of organoclays was definitely more significant than that caused by adding the same amount of free surfactant without clay. The effect of organoclays on the rheological properties was insignificant in all tested systems, suggesting weak interactions between the clay particles and the polymer matrix. In the PS system, PMMA, and organoclay the extent of clay exfoliation and the resultant properties are controlled by the compatibility between the polymer matrix and the surfactant rather than by interactions between the polymer and the clay surface. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 44–54, 2003     

Production of submicron-sized poly(methyl methacrylate) particles by dispersion polymerization with a poly(dimethylsiloxane)-based azoinitiator in supercritical carbon dioxide

 Submicron-sized, comparatively monodisperse poly (methyl methacrylate) particles were produced by dispersion polymerization of methyl methacrylate with a poly(dimethylsiloxane)-based azoinitiator in supercritical carbon dioxide at 30 MPa for 24 h at 65 °C. The initiator operated not only as a radical initiator but also as a colloidal stabilizer, and was named an “inistab”. Received: 13 February 2001 Accepted: 20 June 2001     

Poly(methyl methacrylate) hollow particles by water-in-oil-in-water emulsion polymerization

Poly(methyl methacrylate) particles having hollow structures were produced by water-in-oil-in-water (W/O/W) emulsion polymerization where sorbitan monooleate (Span80) was used as a primary surfactant and sodium laurylsulfate and Glucopen (APG, polypeptide derivative) were used as secondary surfactants. Urethane acrylate having a molecular structure with a hard segment in the molecular backbone, a long soft segment in the middle, and vinyl groups at both ends was employed as a reactive viscosity enhancer. At low concentration of urethane acrylate, only a few particles contained a void in the polymer phase. However, as the concentration of urethane acrylate increased, the number of the particles containing the void increased. This was because urethane acrylate increased the viscosity of the monomer mixture and helped to form the stable W/O/W emulsion droplets, which possibly restricted droplet coalescence during emulsion polymerization. Moreover, at high concentration of urethane acrylate (above 7 wt%), multi-hollow-structured particles were obtained. It is believed that the increase in the lyophilicity of the monomer mixture caused by urethane acrylate led to stronger interfacial activity of the primary surfactant (Span80) and finally resulted in many internal aqueous droplets. Received: 31 July 1998 Accepted: 13 October 1998