Synthesis And Characterization Of Hairy Macromolecules Attached On The Surface Of Polystyrene Particles

There are two approaches to prepare the hairy particles: physical adsorption and chemical grafting. "Chemical grafting" methods 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 macromolecular brushes.Firstly, micron-size monodisperse polystyrene (PS) particles were prepared by emulsifier-free polymerization. Then the photo-initiator with double bond and ester group were attached on the surface of the PS particles by copolymerization using "starve" addition together with styrene. Finally both poly(acrylic acid) (PAA) and poly(N-isopropylacrylamide) (PNIPA) as hybrid hairy homopolymers were grafted on the surface of the PS particles by "grafting from" photo-initiation with sequential addition of AA and NIPA. The results showed that the thermo-sensitivity of hairy PNIPA changed obviously in the presence of hairy PAA as polyelectrolyte.4-cyanopentanoic acid dithiobenzoate as soluble reversible addition-fragmentation chain transfer (RAFT) agent was directly added into the above PS particles with photo-initiator on the surface and NVP or NIPA as monomer. There were significant differences between the resulting hairy particles with and without aqueous RAFT agent. Based on living/controlled free radical polymerization mechanism using RAFT agent, it would be estimated that grafting polymerization from the surface of PS particles should be controlled due to obvious retardance phenomena. Moreover, both FTIR and GPC were used to characterize the hairy homopolymers, which were scissored from the shell surface through hydrolysis of the ester group of photo-initiator. In FTIR spectrogram of scissored PVP or PNIPA, characteristic peak of C=S double bond were discovered. It is to say that the patch of RAFT agent on the hairy chains.PS particles with the shell of copolymer of styrene and vinylbenzyl chloride (VBC) were prepared by similar seeded and starved addition processes. RAFT agent with carboxyl end-group attached on the shell surface of PS particles by group reaction. Adding NIPA and photo-initiator into the continuous phase of polymerization system, hairy PNIPA were obtained.