Effective dispersion of fullerene with methacrylate copolymer in organic solvent and poly(methyl methacrylate)

Dispersion of fullerene, C₆₀, by addition of polymethacrylate dispersant in methyl methacrylate (MMA) and incorporation of C₆₀ into poly(methyl methacrylate) (PMMA) were investigated. Copolymers synthesized by radical copolymerization of MMA and 2-naphthyl methacrylate (NMA), poly(MMA-co-NMA), effectively dispersed C₆₀ in MMA to form clusters of 20?nm. In these cases, addition of minimal 110 naphthyl groups per unit C₆₀ molecule afforded to give clusters with minimum of 20?nm sizes. Furthermore, block copolymers, poly(MMA-b-NMA) with MMA/NMA mole ratio from 12:1 to 20:1, also efficiently dispersed C₆₀ to give formation of clusters of 20?nm size by addition of minimal 40 naphthyl groups per unit C₆₀ molecule, which was corresponding to approximate nine layers of naphthyl group in block copolymer adsorbed on the surface of the cluster. Hybrid films of C₆₀/PMMA, prepared by casting of C₆₀-dispersed solution containing PMMA, exhibited absorbance at 400?nm linearly increased with C₆₀ content.     

Characterization and degradation of the poly(methylphenylsiloxane)–poly(methyl methacrylate) graft copolymer

Poly(methylphenylsiloxane)–poly(methyl methacrylate) graft copolymers (PSXE-g-PMMA) were prepared by condensation reaction of poly(methylphenylsiloxane)-containing epoxy resin (PSXE) with carboxyl-terminated poly(methyl methacrylate) (PMMA), and they were characterized by gel permeation chromatography (GPC), infrared (IR), and ²⁹Si and ¹³C nuclear magnetic resonance (NMR). The microstructure of the PSXE-g-PMMA graft copolymer was investigated by proton spin–spin relaxation T₂ measurements. The thermal stability and apparent activation energy for thermal degradation of these copolymers were studied by thermogravimetry and compared with unmodified PMMA. The incorporation of poly(methylphenylsiloxane) segments in graft copolymers improved thermal stability of PMMA and enhanced the activation energy for thermal degradation of PMMA. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2521–2530, 1998     

Novel poly(methyl methacrylate)-based ionomers used as multifunctional aids to modify poly(vinyl chloride)

Poly(methyl methacrylate)(PMMA) based ionomers with different lanthanum(La(Ⅲ)) contents(PMMA-XLa) synthesized by free radical solution polymerization were applied to poly(vinyl chloride)(PVC) resins as a kind of multifunctional aids, and their performances were evaluated by measuring the static stability time, initial discoloration, transparency, fusion behavior and tensile strength of the modified PVC. The ionomers with proper lanthanum(La(Ⅲ)) contents show a better thermal stability efficiency in comparison with traditional stabilizer lanthanum stearate. Meantime, they can accelerate PVC plasticization more efficiently than PMMA. The rigid PVC products stabilized with the ionomers present good transparency and enhanced tensile strength.     

An amphiphilic graft copolymer as a surface-modifying additive for poly(methyl methacrylate)

An amphiphilic graft copolymer was prepared by transesterification of poly(2-ethylhexyl acrylate-co-methyl methacrylate) with poly(ethylene glycol) monomethyl ether (MPEG2000). The grafting reaction was performed in melt at 155°C. The purified graft copolymer was blended into poly(methyl methacrylate) in concentrations of 1.5-30 wt %, either by mixing in chloroform solution or by melt mixing by means of a twin-screw extruder or a Brabender blender. Films of the blends were prepared by solution casting onto glass plates or by hot pressing between polished Al plates. At concentrations up to 20% of the graft copolymer homogeneous blends were obtained. At higher concentrations the blends were heterogeneous, and side-chain crystallinity was detectable by DSC analysis. The surface properties of the films were studied by measurements of water contact angles. The surface accumulation of the graft copolymer was demonstrated as a large increase in the wetting angle hysteresis, and found to depend on the procedure for film preparation as well as the casting substrate. © 1995 John Wiley & Sons, Inc.     

Thermomechanical investigation of a thick film of aniline-formaldehyde copolymer and poly(methyl methacrylate)

A thick film of aniline-formaldehyde copolymer and PMMA is synthesized via dispersion of aniline-formaldehyde copolymer powder as filler particles in PMMA with two different concentrations. Variation of the complex elastic modulus and mechanical loss factor (tanδ) with temperature is studied. It is observed that the complex elastic modulus decreases with temperature owing to thermal expansion of films. On the other hand, tanδ increases up to a characteristic temperature beyond which it shows a decreasing trend toward melting. Transition temperature T _g of sample S₁ (pure PMMA) is found to be 80°C. In sample S₂ (1 wt % aniline formaldehyde copolymer), the peak of tanδ at a lower temperature (66°C) corresponds to glass transition temperature T _g of the PMMA matrix, while the peak of tanδ at a higher temperature (107.8°C) corresponds to T _g of a polymer chain restricted by filler particles of aniline-formaldehyde copolymer. A further increase (10 wt % aniline-formaldehyde copolymer) in the concentration of filler particles of aniline-formaldehyde copolymer results in a more compact structure and a shift of T _g to a higher temperature, 122.2°C. This shift in the glass transition temperature of thick films of aniline-formaldehyde copolymer and PMMA is dependent upon the concentration of filler particles in the sample.     

Surface and solution properties of polysiloxane–poly(methyl methacrylate) graft copolymer

A polysiloxane–poly(methyl methacrylate) (PMMA) graft copolymer was prepared by hydrosilylation reaction between a Si? H containing polysiloxane and an allyl-terminated PMMA. The obtained graft copolymer was blended with PMMA homopolymer. The addition of only 0.01 wt % of graft copolymer was sufficient to make PMMA surfaces hydrophobic. In acetone–cyclohexane mixed solvent, the graft copolymer formed a polymeric micelle by the aggregation of PMMA branches.     

Photodegradation of poly(methyl methacrylate)

The vacuum photodegradation at 30°C. of poly(methyl methacrylate) and copolymers with acrylaldehyde, methacrylaldehyde, and methyl acrylate has been studied. The polymers were examined in the form of expanded films as produced by a freeze-drying technique. At least one molecule of carbon monoxide is evolved for each chain scission. It is concluded that chain scission in poly(methyl methacrylate) is primarily the result of photoinduced aldehyde groups.     

Micellization in solutions of hybrid block copolymer of poly(methyl methacrylate) and hyperbranched perfluorinated poly(phenylene germane)

Fractions of the product resulting from the polymerization of methyl methacrylate in the presence of hyperbranched perfluorinated poly(phenylene germane) have been studied by dynamic and static light scattering and capillary viscometry in methyl ethyl ketone solutions. The hybrid product is obtained via the reaction of the chain transfer of methyl methacrylate propagating radicals to pentafluorophenyl groups. Eight fractions have been isolated by fractional precipitation, including fractions of the linear-dendrite block copolymer. Light scattering studies have shown that hybrid macromolecules containing 15–20 wt % hyper-branched fragments form micelles in solutions.     

Dynamics of adsorbed poly(methyl acrylate) and poly(methyl methacrylate) on silica

Deuterium NMR and modulated differential scanning calorimetry (MDSC) were used to probe the behavior of ultrathin adsorbed poly(methyl acrylate) (PMA). The spectra for the bulk methyl-labeled PMA-d₃ were consistent with the motions of the polymer segments being spatially homogeneous. For the polymers adsorbed on silica, multicomponent line shapes were observed. The segmental mobility of the surface polymers increased with increased adsorbed amounts. In contrast to the behavior of the polymers in bulk, the adsorbed lower-molecular-mass PMA-d₃ was less mobile than the adsorbed high-molecular-mass polymer. The presence of a polymer overlayer was sufficient to suppress the enhanced mobility of the more-mobile segments of the adsorbed (inner) polymer. MDSC studies on adsorbed poly(methyl methacrylate) showed that the glass-transition temperature of the thin polymer films increased and broadened compared to the behavior of the polymer in bulk. The presence of a motional gradient with the less-mobile segments near the solid-polymer interface and the more-mobile segments near the polymer-air interface was consistent with the experimental observations.     

Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with poly(butadiene-block-methyl methacrylate)

Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with butadiene-methyl methacrylate diblock copolymers has been investigated by transmission electron microscopy. When the diblock copolymers are added to the blends, the size of PB particles decreases and their size distribution gets narrower. In PB/PMMA7.6K blends with P(B-b-MMA)25.2K as a compatibilizer, most of micelles exist in the PMMA phase. However, using P(B-b-MMA)38K as a compatibilizer, the micellar aggregation exists in PB particles besides that existing in the PMMA phase. The core of a micelle in the PMMA phase is about 10 nm. In this article the influences of temperature and homo-PMMA molecular weight on compatibilization were also examined. At a high temperature PB particles in blends tend to agglomerate into bigger particles. When the molecular weight of PMMA is close to that of the corresponding block of the copolymer, the best compatibilization result would be achieved. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 85–93, 1998     

Methanol-induced opacity in poly (methyl methacrylate)

Methanol-induced opacity in poly (methyl methacrylate) (PMMA) is investigated subject to two cooling processes; furnace cooling and air cooling. The glass transition temperature of PMMA decreases with increasing time of exposure to methanol at 40–60°C and then increases during cooling, due to progressive desorption. Voids form during cooling as long as specimen temperature remains above its glass transition temperature. Since furnace cooling affords enough time for holes to expand larger than the light wavelengths, the transmittance of furnace-cooled PMMA is independent of wavelength. The transmittance of PMMA subjected to rapid cooling in the air is wavelength dependent due to scattering by holes smaller than light wavelengths. The transmittance of PMMA bearing a given weight gain of methanol (measured at absorption temperature) prior to cooling for furance cooling is lower than that for the same material subjected to air cooling. A sharp front between outer and inner regions is found in specimens removed quickly from the thermostated water bath to air at ambient temperature.     

Thermoluminescence of irradiated poly(methyl methacrylate)

Thermoluminescence of poly(methyl methacrylate) (PMMA) irradiated with x rays, has been studied in the temperature range 100 to 460°K. Two glow peaks with maxima at 136 and 368°K have been observed. These are analyzed by three methods and the results are compared. Both curves obey second order kinetics and correspond to activation energies of 0.17 and 0.88 eV, respectively. It is possible to identify the centers responsible for the two peaks by correlation with electron spin resonance and optical data obtained for the same samples irradiated under the same conditions. Spectral studies of the emission show that the low temperature peak has its maximum at 365 nm while the high temperature peak has its maximum at 480 nm.     

Micellar and surface properties of a poly(methyl methacrylate)-block-poly(N-isopropylacrylamide) copolymer in aqueous solution

Critical micelle concentrations (cmc) of aqueous solutions of poly(methyl methacrylate)-block-poly(N-isopropylacrylamide) were determined at several temperatures by surface tensiometry. Below the lower critical solution temperature (LCST), the low Delta mic H 0 determined can be assigned to the PMMA block being tightly coiled in the dispersed molecular state, so that the unfavorable interactions of hydrophobic entities with water are minimized. Above the LCST the cmc value was found to increase; an anomalous behavior that can be directly related to the micelle-globule transition of the hydrophilic block. Interestingly, above the LCST the surface tension of relatively concentrated solutions was found to depend weakly on temperature not following the usual strong decrease with temperature expected for aqueous solutions.     

Electron-beam charging of poly(methyl methacrylate)

The charging of bulk poly(methyl methacrylate) by irradiation with electrons of 2 MeV energy at room temperature in vacuum was studied. The experimental data obtained using the split Faraday cup are compared with the results of numerical simulation assuming one-dimensional geometry with allowance for the spatial distribution of dose rate and injected-electron current, nonlinear properties of radiation-induced conductivity in the prebreakdown electric-field region, and the intrinsic conductivity of poly(methyl methacrylate). It was shown that published data on the electric field strength measured by means of the electro-optical Kerr effect in electron-beam charged poly(methyl methacrylate) agree satisfactorily with the calculation results.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 3, 2005, pp. 183–189.Original Russian Text Copyright © 2005 by Sadovnichii, Tuytnev, Milekhin.     

Synthesis of poly(methyl methacrylate) macromonomer

Anionic polymerization of methyl methacrylate (MMA) was carried out in tetrahydrofuran (THF) or THF/toluene mixture at ?78°C initiated by triphenylmethyl sodium or lithium as initiators. Highly syndiotactic PMMA of low polydispersity (M _w/m _n = 1.11–1.17) could be prepared with triphenylmethyl lithium in THF or THF/toluene mixture at ? 78°C. Moreover, PMMA macromonomer having one vinylbenzyl group per polymer chain was prepared by the couplings of living PMMA initiated by triphenylmethyl lithium with p-chloromethyl styrene (CMS) at ?78°C. The coupling reaction of living PMMA initiated by triphenylmethyl sodium with CMS was scarcely occurred.     

Preparation of water dispersible poly(methyl methacrylate)-based vesicles for facile persistent antibacterial applications

We report a facile strategy for incorporating persistent and effective antibacterial property into a widely used polymer, poly(methyl methacrylate)(PMMA), by copolymerizing methyl methacrylate(MMA) with 2-(tert-butylamino)ethyl methacrylate(TA) in one pot via atom transfer radical polymerization(ATRP). The subsequent self-assembly of the resultant poly(methyl methacrylate)-block-poly[(2-tert-butylamino)ethyl methacrylate](PMMA20-b-PTA15) diblock copolymer affords well-defined water-dispersible vesicles, which can be facilely sprayed on the walls in hospitals for effective inhibition and killing of bacteria. 1H-NMR and gel permeation chromatography(GPC) studies confirmed the successful synthesis of welldefined copolymer. Transmission electron microscopy(TEM), atomic force microscopy(AFM) and dynamic light scattering(DLS) studies proved the formation of vesicles with narrow size distribution. DLS studies revealed the excellent stability of vesicles at various temperatures. Antibacterial tests showed effective antibacterial activities of polymer vesicles against both Gram-positive and Gram-negative bacteria. Moreover, this strategy may be extended for preparing a wide range of polymeric materials for facile antibacterial applications in many fields.     

Branching of anionic poly(methyl methacrylate)

A viscometric determination of the degree of branching γ, of poly(methyl methacrylate) obtained by anionic polymerization proved the reaction of the growing center of poly(methyl methacrylate) with the ester group of another polymer molecule, accompanied by the formation of a trifunctional branch point. This reaction occurs if the solution polymerization of methyl methacrylate is initiated: (1) with butyllithium at ?78°C only on attaining 100% conversion and after a long time or at +20°C immediately after the polymerization has set in; (2) with lithium tert-butoxide at +20°C after a long time. The degree of branching of poly(methyl methacrylates) obtained under similar conditions in the presence of tetrahydrofuran reaches higher values than for polymers prepared in toluene. The tacticity of polymers does not affect the experimentally determined γ values.