Synthesis of well-defined bisbenzoin end-functionalized poly(-caprolactone) macrophotoinitiator by combination of ROP and click chemistry and its use in the synthesis of star copolymers by photoinduced free radical promoted cationic polymerization.

A new well-defined bisbenzoin group end-functionalized poly(-caprolactone) macrophotoinitiator (PCL-(PI)) was synthesized by combination of ring opening polymerization (ROP) and click chemistry. The ROP of -CL monomer in bulk at 110 °C, by means of a hydroxyl functional initiator namely, 3-cyclohexene-1-methanol in conjunction with stannous-2-ethylhexanoate, (Sn(Oct)), yielded a well-defined PCL with a cyclohexene end-chain group (PCL-CH). The bromination and subsequent azidation of the cyclohexene end-chain group gave bisazido functionalized poly(-caprolactone) (PCL-(N)). Separately, an acetylene functionalized benzoin photoinitiator (PI-alkyne) was synthesized by using benzoin and propargyl bromide. Then the click reaction between PCL-(N) and PI-alkyne was performed by Cu(I) catalysis. The spectroscopic studies revealed that poly(-caprolactone) with bisbenzoin photoactive functional group at the chain end (PCL-(PI)) with controlled chain length and low-polydispersity was obtained. This PCL-(PI) macrophotoinitiator was used as a precursor in photoinduced free radical promoted cationic polymerization to synthesize an AB-type miktoarm star copolymer consisting of poly(-caprolactone) (PCL, as A block) and poly(cyclohexene oxide) (PCHO, as B block), namely PCL(PCHO).