Synthesis And Characterization Of Polystyrene Particles With Polymer Brushes

Generally, there are two schemes to prepare the polymer brushes: (1) physical adsorption. (2) chemical grafting. "Chemical grafting" method includes two techniques. One is "grafting to" and the other is "grafting from". In recent years, the "grafting from" approach has attracted considerable attention in the preparation of tethered polymers on a solid substrate surface because it can obtain high density for polymer brushes. The uniform polystyrene particles with polyelectrolyte brusheds(PAA) and thermo-sensitive brushes (PNIPAM) have been synthesized successfully three key steps. Firstly, the monodisperse PS particles were synthesized by emulsifier-free polymerization. Secondly, the photo-initiator with double bond and ester group were attached on the surface of the PS particles as paper-thin shell by copolymerization using "starve" addition with styrene or acetone, which control the grafting density of brushes. Finally, we successfully obtained the uniform polymer particles with PS core and macromolecular brushes.Photo-initiator Darocur(?)methacrylate with double bond and ester group was synthesized. Both 1H NMR and 13C NMR spectroscopy were used to confirmed the structure of the photoinitiator with high purity.The monodisperse micron-size polystyrene particles were prepared by emulsion-free emulsion polymerization. The effect of pH value, styrene concentration and potassium persulfate(KPS) content on conversion, particle size and its distribution were mainly investigated. The results indicated that it was useful method for addition of both NaOH and NaHCO3 mixed solvent to control polymerization kinetics, size and its monodispersity of obtained particles. With increasing the basic mixture as both pH alleviant and electrolyte, final conversion decreased and maximum of particle size existed. Conversion increased with increasing initiator content at the early stage of polymerization process. However, the final conversion might be lower if excessive KPS was added because the decomposition of persulfate was accelerated and initiatorconsume rapidly at lower pH value. On the other hand, particle size distribution became broad while KPS content was lower. The influence of limited change of monomer concentration on polymerization rate could be neglected. Particle size enlarged with higher solid content. However, unstability and broad distribution occurred if monomer concentration tended to be higher.TEM, AFM, DLS, Electrical conductance, GPC and IR were used to confirmed the structure of colloidal brushes. The influence of monomer concentration, seed content, photoinitiator content on the length of brushes and surroundings of test on morphology of brushes were studied. With increasing reaction time, monomer concentration and photoinitiator content, the diameter of particles with polymer brushes increased. Moreover, The "length" of polyelectrolyte brushes increased with adding seed content. However, when seed content increased to some extent, the "length" of polyelectrolyte brushes decreased with increasing of seed content. At the same time, surroundings of test had effect on the diameter of particles with polyelectrolyte brushes. With decreasing of pH value and increasing of ionic strength, the diameter decreased. GPC was used to characterize the separate poly(acrylic acid) brushes, which were cutted out from designed ester group of photo-initiator on the shell surface of polystyrene cores by hydrolysis. Molecular weight with double peaks was independent of the variation of reaction time, AA content and seed content.A hairy uniform polystyrene particles with poly(N-isopropylacrylamide) brushes were prepared. DLS, GPC and IR were used to confirmed the structure of colloidal brushes. The diameter of PS particles with thermo-sensitive brushes increased with increasing of reaction time. However, the diameter decreased with increasing of temperature of test. GPC was used to characterize the separate poly(N-isopropylacrylamide) brushes. Molecular weight was independent of the variation of reaction time. Moreover, the distribution...