Summary: Poly(methyl methacrylate)s (PMMAs) containing a terminal hydroxy group or multiple hydroxy groups as pendants were grafted to multiwalled carbon nanotubes (MWNTs) by esterification in toluene at 100 °C. The recovered polymer with a low level of MWNTs and the PMMA‐g‐MWNTs with up to 12 wt.‐% grafted polymer were characterized using spectroscopic, microscopic, and thermogravimetric analyses. The percentage of polymer present in the PMMA‐g‐MWNT samples is very low based upon the concentration of the acid groups in the tubes.
The grafting of hydroxy‐terminated PMMA to MWNTs by esterification. 相似文献
Stereocomplexes formed in atactic poly(methyl methacrylate) (a-PMMA) films cast form different solvents were studied by means of Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The growth of stereocomplex was a function of annealing temperature and annealing time, respectively. 相似文献
Modulated differential scanning calorimetry has been used to quantify the glass transitions of small adsorbed amounts of poly(methyl methacrylate) (PMMA) on silica. While a relatively narrow, single glass transition was found for bulk PMMA, broader two-component transitions were found for the adsorbed polymer. A two-state model based on loosely bound polymer (glass transition similar to bulk) and more tightly bound polymer (glass transition centered around 156 degrees C) was used to interpret the thermograms. On the basis of this model, the amount of tightly bound polymer was found to be approximately 1.3 mg/m2, corresponding to a 1.1 nm thick layer. The change in heat capacity for the tightly bound polymer at the glass transition temperature was estimated to be about 16% of that of the bulk polymer. 相似文献
New electrospun (ES) sensory fibers consisted of poly(methyl methacrylate) (PMMA) core and poly(3-hexylthiophene-2,5-diyl) (P3HT) shell were successfully prepared using a two-fluid coaxial electrospinning process. Field-emission scanning electron microscope (FE-SEM) studies showed that the prepared ES fibers had diameters of 500–700 nm and worm-like surface structure of P3HT on the fiber. Red emission fibers were exhibited from the laser confocal microscope. Upon exposed to air under light for two weeks, significant blue-shifting on both absorption and luminescence spectra was found on the prepared ES fibers. It was probably due to the chain scission occurred in the P3HT and led to the reduced conjugated length. The sensitivity of the ES fibers was much better than that of the spin-coated P3HT film from the comparison on the variation of photophysical properties. Besides, the EPR result indicated the formation of the P3HT · O2 charge transfer complex (CTC), leading to the fiber conductivity of 10−6 S/cm without an external doping. The present study demonstrates that conjugated polymer based ES core-shell fibers may have potential applications for oxygen-sensing devices. 相似文献
The grafting of the potassium alkoxide derivative of poly(ethylene oxide) on poly(methyl methacrylate) in homogeneous solution in toluene was studied. The alkoxide was prepared by reaction with potassium metal with methanolic potassium methoxide, or with potassium naphthalene. The last was the most suitable for the systematic investigation of the grafting process. Soluble graft polymers were formed, and essentially the initial poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) participated in the production of graft polymer. The composition of the graft polymers and the frequency of grafting of the side chains were determined by NMR. The solubility of the graft polymers in methanol and water increased with increasing PEO contents, while the melting ranges decreased. Fractionation of the crude graft polymers showed that the grafting reaction was random, and graft polymers containing one PEO side chain per about 10–170 MMA units were obtained. 相似文献
The copolymers of methyl methacrylate (MMA) (or styrene (ST))/stearyl methacrylate (SMA) obtained from miniemulsion polymerization
were prepared and characterized. All the miniemulsions showed satisfactory colloidal stability upon aging due to the effectively
retarded Ostwald ripening by the reactive costabilizer SMA. In subsequent miniemulsion copolymerizations, monomer droplet
nucleation predominated in the particle formation process, but homogeneous nucleation could not be ruled out even at such
high levels of SMA (20–50 wt.%). The contact angle first increased rapidly and then leveled off when the SMA content increased
from 20 to 50 wt.% for both the copolymers of MMA/SMA and ST/SMA. At constant level of SMA, the copolymer of MMA/SMA with
a less hydrophobic composition showed a larger contact angle compared to the ST/SMA counterpart. The contact angle (103 ± 1°)
of the copolymer MMA/SMA (50/50 w/w) was comparable to that (104°) of PSMA. A schematic model was proposed to explain the experimental results. 相似文献
Graft copolymers of acrylonitrile and methyl methacrylate on bleached holocellulose and thiolated holocellulose were obtained by the use of ceric ions in aqueous medium at 29°C. The level and efficiency of grafting on the bleached holocellulose were significantly higher than on the thiolated holocellulse, but the molecular weights and number of grafted copolymer chains on both the unmodified and thiolated holocellulose were similar. The graft level and molecular weight of acrylonitrile graft copolymer were significantly lower than those for methyl methacrylate at comparable ceric ion and monomer concentrations. These results indicate the significance of the influence of the polarity of monomer on the extent of graft copolymer formation and lead to the suggestion that graft copolymerization may not result entirely from radicals generated on the cellulose substrate. 相似文献
Chain transfer constants to monomer have been measured by an emulsion copolymerization technique at 44°C. The monomer transfer constant (ratio of transfer to propagation rate constants) is 1.9 × 10?5 for styrene polymerization and 0.4 × 10?5 for the methyl methacrylate reaction. Cross-transfer reactions are important in this system; the sum of the cross-transfer constants is 5.8 × 10?5. Reactivity ratios measured in emulsion were r1 (styrene) = 0.44, r2 = 0.46. Those in bulk polymerizations were r1 = 0.45, r2 = 0.48. These sets of values are not significantly different. Monomer feed compcsition in the polymerizing particles is the same as in the monomer droplets in emulsion copolymerization, despite the higher water solubility of methyl methacrylate. The equilibrium monomer concentration in the particles in interval-2 emulsion polymerization was constant and independent of monomer feed composition for feeds containing 0.25–1.0 mole fraction styrene. Radical concentration is estimated to go through a minimum with increasing methyl methacrylate content in the feed. Rates of copolymerization can be calculated a priori when the concentrations of monomers in the polymer particles are known. 相似文献
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 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.
