Polymers prepared using cleavable initiators: Synthesis, characterization and degradation

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.