Synthesis of degradable model networks via ATRP and click chemistry

A simple scheme involving atom transfer radical polymerization (ATRP) from a bifunctional initiator, conversion of the bromine end groups of the resulting telechelic polymer to azides, and cross-linking of this azido-telechelic macromonomer with multi-acetylene functionalized small molecules via copper-catalyzed azide-alkyne cycloaddition was employed to prepare the first tert-butyl acrylate model networks. This general scheme is wide in scope, enabling synthesis of model networks possessing defined pore size from any monomer polymerizable by ATRP. Introduction of an olefin moiety into the ATRP initiator enabled degradation of the materials by ozonolysis to yield star polymer products bearing three or four arms depending on which cross-linker was employed in the parent network. Size-exclusion chromatography of the ozonolysis products confirmed the pore size of the parent network and yielded insight into the number of unreacted functionalities. Model networks derived from a trifunctional alkyne were found to be more completely cross-linked than those derived from a tetrafunctional alkyne, presumably due to less steric hindrance in the former system.