Synthesis and Characterization of Four-Arm Star Polystyrene Based on a Novel Tetrafunctional RAFT Agent

Reversible addition fragmentation chain transfer polymerization (RAFT) is a very versatile polymerization technique whereby the topology of the final polymer can be tailored using specific RAFT agents. The tetrafunctional RAFT agent, tetrabenzyl(1,3-dithietane-2,2,4,4-tetrayl)-tetracarbanotrithioate, has not previously been used to synthesize polymers. Poly styrene (PS) is synthesized using this tetrafunctional RAFT agent and advanced characterization is performed using spectroscopic and separation methods. In situ H-1 nuclear magnetic resonance spectroscopy (NMR) and size-exclusion chromatography (SEC) are used to determine the topology of the resultant PS. The polymerization is followed by in situ H-1 NMR, using styrene-d(8) rather than hydrogenous styrene. In situ H-1 NMR spectra show that the RAFT agent is incorporated into the polymer as a terminal group. Aminolysis of the star-shaped PS is performed and the SEC and NMR results before and after aminolysis are compared. These results indicate that the expected star-shaped topology of the polymer is achieved.