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Atom transfer radical polymerization: Fundamentals, challenges, and application
Abstract
Various aspects of atom transfer radical polymerization (ATRP) were investigated. In an attempt to find a novel catalyst system for ATRP, we screened the activities of various metal complexes using a combinatorial approach. Several new catalyst systems including FeCl2/bam(TMS) were found to be active ATRP catalysts in the polymerization of styrene and MMA. In order to make this combinatorial screening a viable method of quickly discovering usable systems, we tried to find a fast and reliable method to evaluate the catalysts. A parameter estimation method based on nonlinear regression was developed to evaluate various catalyst systems by determining kinetic parameters of polymerization. From our model system considering small molecular atom transfer addition reaction, we found that equilibrium constant of atom transfer reaction could be successfully estimated. A new model dealing polymerization itself was also developed, and we could demonstrate that each values of activation and deactivation reaction rate constant can be estimated unambiguously. On screening the catalyst systems for ATRP, we found some titanium complexes gave a control in the polymerization of styrene without the aid of Group I–III cocatalysts. A series of experiments to elucidate the mechanism of polymerization all support that radical mechanism is involved in the polymerization using bis-(cyclopentadienyl)titanium dichloride. A possibility of ATRP mechanism was checked by isolating intermediate species. It is found that the polymerization is not followed the pure ATRP pathway, but is comprised of various competing reactions. Several strategies has been developed to prepare polymers having higher order structure including branched, hyperbranched, star, and dendrigrafts. The combination of nitroxide mediated SFRP and ATRP techniques successfully provided relatively simple routes to from branched and hyperbranched polymers in controlled structures. To overcome this limitation of backbone polymer prepared by SFRP, a new strategy using protection-deprotection chemistry was employed. Among the various protected monomers tested, we could prepare branched polystyrene having controlled structure using VBt-BOC and 4-methyl styrene. As an example of diversity of this strategy, we also could prepare the branched acrylate polymer having controlled structure.
Subject Area
Polymers
Recommended Citation
Kwark, Young-Je, "Atom transfer radical polymerization: Fundamentals, challenges, and application" (2001). Doctoral Dissertations Available from Proquest. AAI3027221.
https://scholarworks.umass.edu/dissertations/AAI3027221