Chain-end modification of polymer-iodide synthesized via organocatalyzed living radical polymerization and its application in functional materials

Abstract

Chain-end modification methods of polymer-iodide (polymer-I), which was synthesized via an organocatalyzed controlled radical polymerization, were established in this Thesis. Chain-end functionalized polymers and chain-end reduced polymers were prepared selectively and quantitatively. These methods found useful applications in patterned polymer brushes, chain-end patterned polymer brushes, and rewritable polymer brushes syntheses. Chapter 1 is the general introduction reviewing the synthesis of chain-end functionalized polymers via several controlled radical polymerization methods and the applications of those polymers. Polymer brushes on solid surfaces, chain-end functionalized polymer brushes, and patterned polymer brushes were also introduced for their useful applications in smart surface materials and biomedical materials. The aims and motivations for developing new chain-end modification methods in this thesis were explained. In Chapter 2, a chain-end functionalization method of polymer-I was developed by using primary amines (NH2R) to generate polymer-NHR, where functional groups may be contained in the R moiety. Several functional groups such as OH, phenyl, SH, alkyl, and triethoxysilyl groups were successfully attached at the polymer chain end via a substitution reaction of polymer-I with NH2R. Two representative polymers, i.e., poly(butyl acrylate) and polystyrene, were comprehensively studied and the reaction mechanism was also probed through matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis. The chain-end functionalization was quantitative and easy to operate, which is attractive as a platform technique to produce various chain-end functionalized polymers. In Chapters 3 and 4, novel selective chain-end modification methods were developed using biocompatible cysteamine or combining primary amines with formic acid. By switching UV light on and off, hydrogen-terminated polymer (polymer-H) and various chain-end functionalized polymers were selectively produced, respectively. The photo-induced selective modification was amenable to a range of functional groups. The selective chain-end modification methods were applied to fabricate chain-end patterned polymer brushes. In Chapter 5, rapid and quantitative chain-end modification methods were developed using thiols (RSH, where the R moiety can contain functional groups). Various functional groups such as COOH, alkyl, SH, alkenyl, OH, and phenyl groups were successfully introduced at the polymer chain end through the substitution reaction of polymer-I with RSH. The quantitative conversion was attained rapidly, i.e., in 10 min. By using HSCH2CH2SH, thiol-terminated polymers (polymer-SCH2CH2SH) were prepared. The thiol-functionalization was applied to obtain thiol-terminated polymer brushes on the surface, which was further applied to rewritable polymer brush surfaces.