Ring-opening Polymerization Of CL Research Articles

Modification of Hydroxyapatite Nanosurfaces for Enhanced Colloidal Stability and Improved Interfacial Adhesion in Nanocomposites

This work describes a rational approach of hydroxyapatite (HAp) nanosurface modification for graft polymerization of e-caprolactone (CL). The ring-opening polymerization of CL on HAp surfaces was carried out using three types of HAp with different surface hydroxyl functionality: unmodified HAp (surface OH), HAp modified with l-lactic acid (secondary OH), and HAp modified with ethylene glycol (primary OH). The grafting efficiency and the amount of grafted poly(e-caprolactone) (PCL) were dependent on the nature and steric environment of the hydroxyl groups on the HAp surfaces. Transmission electron microscopy measurements and time-dependent phase monitoring indicated that surface-modified HAp could be more uniformly dispersed in methylene chloride than unmodified HAp, and its colloidal stability increased dramatically as the amount of grafted PCL increased. The nanocomposites of PCL and PCL-grafted HAp showed enhanced tensile strength and toughness, compared with that of unmodified HAp and PCL. Increased i...

Ring-opening polymerization of ε-caprolactone and l-lactide using organic amino calcium catalyst

Poly (ε-caprolactone) (PCL) and poly ( l-lactide) (PLA) were prepared by ring-opening polymerization catalyzed by organic amino calcium catalysts (Ca/PO and Ca/EO) which were prepared by reacting calcium ammoniate Ca(NH 3) 6 with propylene oxide and ethylene oxide, respectively. The catalysts exhibited high activity and the ring-opening polymerization behaved a quasi-living characteristic. Based on the FT-IR spectra and the calcium contents of the catalysts, and based on the 1H NMR end-group analysis of the low molecular weight PCL prepared using catalysts Ca/PO and Ca/EO, it was proposed that the catalysts have the structure of NH 2–Ca–O–CH(CH 3) 2 and NH 2–Ca–O–CH 2CH 3 for Ca/PO and Ca/EO, respectively. The ring-opening polymerization of CL and LA follows a coordination-insertion mechanism and the active site is the Ca–O bond.