Polymers prepared using cleavable initiators: Synthesis, characterization and degradation
Maria D. Rikkou and Costas S. Patrickios
Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus.
Following the great interest in polymers based on degradable monomers and degradable cross-linkers, there is now an increasing activity in the controlled synthesis of polymers using degradable initiators. The degradation of polymers bearing residues of degradable initiators has three unique effects: (a) creation of functional end-groups, (b) controlled reduction in molecular weight, and (c) controlled reduction in the degree of branching. Degradation of such polymers has been done for various reasons, including the production of end-functionalized polymers with freshly prepared thiol end-groups for specific adsorption on to gold surfaces, the transformation of a physical gel to a solution, the conversion of end-linked networks to end-functionalized star polymers and the characterization of their core functionality, and the fabrication of nanoporous membranes by the etching of cylindrical nanophases out of a diblock copolymer film. To date, a variety of labile groups have been employed in these initiators, with most notable example the disulfide, while some other groups are yet to be used.
Keywords:Degradable initiators, Degradable polymers, Reducible disulfide groups, Photocleavable ortho-nitrobenzyl esters, Thermoreversible Diels–Alder adducts, Ozonolyzable olefinic groups.