The chemoenzymatic synthesis of AB-type diblock copolymers from a novel bifunctional initiator

A novel bifunctional initiator 2,2,2-trichloroethanol (TCE) is used for the chemoenzymatic synthesis of AB-type diblock copolymer polycaprolactone-block-polystyrene (PCL-b-PSt) by combination of two fundamentally different synthetic techniques: enzymatic ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) and atom transfer radical polymerization (ATRP) of styrene (St). The kinetic study on the TCE-initiated enzymatic ROP of ε-CL in the presence of the biocatalyst Novozyme-435 was investigated. By optimization of the reaction conditions, TCE quantitatively initiated enzymatic ROP of ε-CL. Trichloromethyl-terminated PCL macromolecules prepared in this way were subsequently employed as macroinitiators in the ATRP of St using CuCl/2,2′-bipyridine as the catalyst system to afford well-defined AB-type diblock copolymers PCL-b-PSt. The kinetic analysis of ATRP indicated a 'living'/controlled radical polymerization. The polymeric nanospheres were prepared by the precipitation method from two resulting PCL-PSt diblock copolymers with different content ratio of PSt to PCL. It was determined by DLS and AFM that two different diameter nanospheres had been obtained.