The use of block copolymers to systematically modify photochromic behavior

Reversible addition fragmentation chain transfer (RAFT) living radical polymerization has been utilized successfully to allow the systematic tuning of photochromic switching rates in a rigid, ophthalmic quality, polymer matrix. Block copolymers of poly(styrene) and poly(n-butyl acrylate) were synthesized using a RAFT functionalized photochromic (spirooxazine) dye. Thus the photochromic dye initiated the polymerizations and allowed the known and precise placement of the dye at the start of the block copolymer chains. The photophysical investigation of these more complex architectures demonstrated that systematic tuning of photochromic rates could be achieved by changing the length and choice of either block. The photochromic rates were significantly more sensitive to the presence of low glass-transition temperature poly(n-butyl acrylate) than high glass-transition temperature poly(styrene), even if the poly(n-butyl acrylate) was the more distant second block from the spirooxazine.