Synthesis of a well-definded telechelic macro azo poly(L-lactide) photoinitiator and its use in block copolymerization

In this thesis, a well-defined telechelic macro azo poly(L-lactide) (PLLA) photoinitiator was synthesized by combining ring-opening polymerization (ROP) and normal condensation methods and used in the synthesis of block copolymer. For this purpose first, a well-defined PLLA macrophotoinitiator (B-PLLA) with benzoin photoactive group (B) at one end of the chain was synthesized via ring-opening polymerization (ROP) of L-lactide monomer in the presence of benzoin (B) initiator and Sn(Oct)2 catalyst. Then, the condensation reaction between synthesized B-PLLA macrophotoinitiator and 4,4′-azobis(4-cyanovaleric acid) (ACVA) gave a polymer with an azo group (-N=N-) in the middle of the chain and benzoin photoactive groups (B) at both ends of the chain, namely, telechelic macro azo PLLA photoinitiator (B-PLLA-N=N-PLLA-B). The obtained macrophotoinitiator was used as a prepolymer in the synthesis of block copolymer. This prepolymer was used as a macroinitiator in the thermal free radical polymerization of styrene (St) monomer to obtain a telechelic block type macrophotoinitiator (B-PLLA-PSt-PLLA-B). Characterization of the macrophotoinitiators was performed by FT-infrared, 1H NMR, GPC, UV-Vis and fluorescence measurements. In the last step, an ABCBA type five-block copolymer was obtained by using the telechelic B-PLLA-PSt-PLLA-B macrophotoinitiator as a prepolymer in the photoinduced free radical promoted cationic polymerization of cyclohexene oxide (CHO) monomer. Characterization of the synthesized ABCBA type block copolymer was done by FT-infrared, 1H NMR, and GPC techniques.