Development of Thermal and Photochemical Strategies for Thiol−Ene Click Polymer Functionalization

• Published in: Macromolecules Vol. 41; no. 19; pp. 7063 - 7070
• Main Authors: Campos, Luis M, Killops, Kato L, Sakai, Ryosuke, Paulusse, Jos M. J, Damiron, Denis, Drockenmuller, Eric, Messmore, Benjamin W, Hawker, Craig J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 14.10.2008
• Subjects: Applied sciences; Chemical modifications; Chemical reactions and properties; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; 1,3-Dipolar cycloaddition; End group; Telechelic polymer; Propargylic compound; Methyl methacrylate polymer; Photochemical reaction; Thermal reaction; Styrene derivative copolymer; Mercaptoacid; Lateral group; Ethylene oxide polymer; Caprolactone copolymer; Styrene polymer; Chemical reactivity; Thiol; Lactone copolymer; Experimental study; Methyl methacrylate copolymer; Sulfur copolymer; Chemical modification; Preparation; Addition reaction; Methacrylate copolymer; Aliphatic copolymer; Styrene copolymer
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma801630n

A series of alkene-functional polymers were synthesized by controlled polymerization techniques in order to investigate and compare the efficiency and orthogonality of both photochemically and thermally initiated thiol−ene click coupling reactions. The copolymers were designed to have single or multiple alkene-functional groups along the backbone, and to evaluate the robustness of these procedures, functionalization reactions with a library of mercaptans were studied. In comparing the photoinitiated reaction to its thermal counterpart, the thiol−ene photocoupling was found to proceed with higher efficiency, require shorter reaction times for complete conversion, and displayed a higher tolerance to various backbones and functional groups. To examine the orthogonality of the thiol−ene click reaction, an asymmetric telechelic polymer based on PS was designed with alkene functionality at one end and an azide at the other. The thermally initiated thiol−ene coupling was found to be completely orthogonal with the traditional azide/alkyne click reaction allowing the individual chain ends to be quantitatively functionalized without the need for protection/deprotection strategies. From these studies, the demonstrated efficiency and orthogonality of thiol−ene chemistry shows it to be a practical addition to the family of click reactions that are suitable for polymer functionalization.