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

• l-Lactide was utilized to modify BBL under free-solvent using TBD as the catalyst
• The hydrophobicity of PLLA was successfully imparted into BBL, particularly on the surface
• The BBL-g-PLLA copolymer coating film exhibits good UV-absorbent ability
• Improved utilization of biobutanol lignin (BBL)

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, 1H NMR and 13C 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.

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