Preparation of a star-type telechelic macrophotoinitiator of poly(epsilon-caprolactone) and its use in photoinduced free radical promoted cationic polymerization

摘要

A novel and well-defined four-arm star-type telechelic macrophotoinitiator of poly(epsilon-caprolactone) carrying benzoin photofunctional end-groups (PCL-BPI)(4) was successfully synthesized by the combination of ring opening polymerization (ROP) and click chemistry techniques. First, hydroxyl end-functionalized four-arm (PCL-OH)(4) was synthesized by ROP of epsilon-caprolactone (epsilon-CL) with pentaerythritol initiator. Then, the hydroxyl groups at the chain ends were converted to terminal alkyne groups by the condensation reaction between (PCL-OH)(4) and 4-pentynoic acid to give an alkyne end-functionalized four-arm poly(epsilon-caprolactone), (PCL-alkyne)(4), as the first click couple compound. Separately, an azido end-functionalized benzoin photoinitiator (BPI-N-3) was prepared in two steps to be used as the other click couple compound. (PCL-alkyne)(4) and BPI-N-3 were coupled via click chemistry to prepare a well-defined four-arm star-type telechelic macrophotoinitiator, (PCL-BPI)(4.) In addition, the obtained (PCL-BPI)(4) macrophotoinitiator was used in the photoinitiated free radical promoted cationic polymerization of cyclohexene oxide (CHO) to produce an (AB)(4)-type star shaped block copolymer, (PCL-PCHO)(4). All the polymers prepared were characterized by different spectral and analytical methods and their thermal behaviors were investigated.