Combination of lignin and L-lactide towards grafted copolymers from lignocellulosic butanol residue

A series of BBL-graft-poly (L-lactide) copolymers were synthesized via ring-opening polymerization (ROP) of L-lactide (L-LA) with a biobutanol lignin (BBL) initiator and a triazabicyclodecene (TBD) catalyst under free-solvent at 135 °C. By manipulating the mass ratio of BBL/LLA, BBL-g-PLLA copolymers with tunable number-average molecular weight (Mn) (2544-7033 g mol(-1)) were obtained. The chemical structure of PLLA chains was identifiable by FT-IR, (1)H NMR and (13)C NMR spectroscopies, in combination with UV-vis spectra to provide support for the existence of the BBL in the copolymer. This provided solid evidence for the successful synthesis of BBL-g-PLLA copolymer. The thermal properties and surface characterization of BBL-g-PLLA copolymers were different from those of linear PLLA. Furthermore, the BBL-g-PLLA copolymer film showed good absorption capacity in the UV region and high transparency in the visible light region, which was expected to find significant applications in UV-protective coating film.