Synthesis and characterization of Novel super-fine paricle-sized polymers

Abstract

The objectives of this research work are the synthesis and characterization of the super-fine particles of poly(styrene-co-methyl methacrylate) by a dispersion copolymerization technique. Dispersion copolymerization of styrene and methyl methacrylate was carried out in the mixed solvent of ethanol and n-hexane where poly(methyl vinyl ether) was used as a matrix polymer. The copolymer compositions were identified by NMR and EA, the particle sizes were characterized by SEM, the average-molecular weights by GPC, FT-IR was used to characterize the functional groups, XPS was used for the surface analysis and DSC, TG/DTA were for the thermal analysis. The effects of matrix polymer, feed ratios, solvent mixing ratios and reaction temperatures were also investigated. To study the effect of the matrix polymer, solution and bulk copolymerizations were also carried out under the same set of conditions in the absence of PMVE. The results indicated that all the dispersion copolymer particles were obtained in a spherical shape with the size range of 1-5µm. The average-molecular weights became lager in the smaller particles. In contrast, when the systems were polymerized without the PMVE matrix polymer, the copolymers in solution and bulk copolymerizations were aggregated and formed in random shapes. It was found that the biggest and smallest particles were obtained in the homopolymers of PMMA and PS, respectively. When increasing the styrene feed, the particle sizes decreased with a narrower size distribution. The particle sizes of the dispersion copolymers were found to be controlled by changing the solvent mixing ratios. The increase in ethanol content resulted in smaller particle sizes. Solubility of the matrix polymer containing a good solvent is probably the main factor controlling the morphology of the matrix polymer and providing different free volumes of the polymerizing system that leads to different particle sizes. However, the bigger particles were not found in the 0 and 20% ethanol contents; surprisingly, the particle size and size distribution of the copolymers were very small with narrow distributions. The appropriate temperature range for this dispersion copolymerization was 50 to 64 ℃. The reaction did not occur at 40℃ and it gave the agglomerated particles at 73℃. The particle size and size distribution were increased and became broader with increasing the reaction temperatures. The effects of each parameter were discussed.