Synthesis of liquid crystalline-amorphous block copolymers by the combination of atom transfer and photoinduced radical polymerization mechanisms

The synthesis of ABA-type block copolymers, involving liquid-crystalline 6-(4-cyanobiphenyl-4′-oxy)hexyl acrylate (LC6) and styrene (St) monomer with copper-based atom transfer radical polymerization (ATRP) and photoinduced radical polymerization (PIRP), was studied. First, photoactive α-methylol benzoin methyl ether was esterified with 2-bromopropionyl bromide, and it was subsequently used for ATRP of LC6 in diphenylether in conjunction with CuBr/N,N,N′,N″,N″-pentamethyldiethylenetriamine as a catalyst. The obtained photoactive functional liquid-crystalline polymer, poly[6-(4-cyanobiphenyl-4prime;-oxy)hexyl acrylate] (PLC6), was used as an initiator in PIRP of St. Similarly, photoactive polystyrenes were also synthesized and employed for the block copolymerization of LC6 in the second stage. The spectral, thermal, and optical measurements confirmed a full combination of ATRP and PIRP, which resulted in the formation of ABA-type block copolymers with very narrow polydispersities.