One-pot Near-ambient Condition AI-RAFT for Star Polymer Synthesis

A near-ambient and oxygen tolerant arm-first star polymer synthesis strategy was developed using alkylborane-initiated reversible addition-fragmentation chain transfer (AI-RAFT). An air stable alkylborane-amine complex was chemically deblocked with isocyanate functionalities in-situ to liberate a reactive alkylborane that consumes oxygen to generate radicals to drive the RAFT processes. The AI-RAFT system was optimized for oxygen and initiator concentration as well as reaction time to improve livingness and further improve star conversion. Crosslinking agents were injected at the conclusion of arm polymerizations to yield star polymers, which were evaluated by arm-conversion values, arm numbers, and dispersities. To assess the tunability of star morphology, systematic studies were performed to evaluate the influence of monomer concentration, crosslinker functionality, crosslinker concentration, and the degree of polymerization of the arms. Our experimentation revealed that the functionality of the crosslinker had little effect on conversion of arms to stars, but that the ratio of the alkene to the CTA caused significant changes in arm conversion and arm numbers. Last, the star polymers produced by AI-RAFT were converted into poly(acrylic acid) stars and evaluated for use as polyelectrolyte complexes.M.S., Materials Science and Engineering -- Drexel University, 201