Synthesis of mid-chain functional macrophotoinitiators of poly(D,L-lactide) homopolymer and tetrablock poly(D,L-lactide)-poly(ε-caprolactone) copolymer by ring-opening polymerization

Abstract

We have synthesized novel biobased and environmental friendly mid-chain functional macrophotoinitiators of poly(D,L-lactide) homopolymer (PDLLA-PI-PDLLA) and tetrablock poly(D,L-lactide)-poly(ε-caprolactone) copolymer (PDLLA-PCL-PI-PCL-PDLLA) with controlled molecular weights and narrow molecular weight distributions via ring-opening polymerization (ROP). Mid-chain functional poly(D,L-lactide) (PDLLA-PI-PDLLA) macrophotoinitiator was prepared by ROP of D,L-lactide (DLLA) monomer using a dihydroxy-functional photoinitiator (HO-PI-OH) as the initiator and stannous-2-ethyl hexanoate (Sn(Oct)2) as the catalyst. Tetrablock poly(D,L-lactide)-poly(ε-caprolactone) copolymer (PDLLA-PCL-PI-PCL-PDLLA) with a mid-chain photofunctional group was synthesized via sequential ROP of ε-caprolactone and D,L-lactide using Sn(Oct)2 as the catalyst. The resultant polymers were fully characterized by means of 1H NMR, FTIR, UV-vis, Fluorescence, and GPC techniques. The obtained macrophotoinitiators were used as a prepolymer in photoinitiated free radical polymerization for obtaining AB-type diblock copolymer and ABC-type triblock terpolymer.