Biobased diblock copolymers and associated reactivity ratios via RAFT-polymerisation as new dispersing additives

Abstract

Diblock copolymers with structural heterogeneity, made of monomers based on renewable resources were investigated as dispersing additives for nonpolar coating systems. Reversible addition–fragmentation transfer (RAFT) polymerisation was used to obtain (diblock co)polymers with tailor-made structures and molecular weights M_w. For this purpose methacrylates derived from oleyl alcohol and eugenol, were utilized. The reaction kinetics of controlled and free radical polymerisation processes for methacrylated eugenol (4-allyl-2-methoxyphenyl methacrylate) (1) and methacrylated oleyl alcohol (octadec-9-en-1-yl methacrylate) (2) were investigated. In addition, commercially available methacrylates – including methyl methacrylate (3), methacrylic acid (4), benzyl methacrylate (5) and stearyl methacrylate (6) were used for building diblock copolymers. Reaction kinetics of the homopolymers 3 and 6 were compared to those of methacrylates 1 and 2. By RAFT-Polymerisation of Methacrylate 1, pronounced cross-linking was observed, suggesting the active participation of the allyl group. Subsequent investigations confirmed that the allyl group underwent partial conversion. By lowering the concentration, the cross-linking reaction could be minimized, enabling the synthesis of diblock copolymers. Finally, their performance as dispersing additives was evaluated in non-polar coating systems containing inorganic and carbon black pigments. To measure performance, properties such as rheological behavior and particle size distribution were analysed. All diblock copolymers showed good dispersity properties for all pigments, with particularly pronounced effects for the fully bio-based block copolymer poly(2-b-4) and the partially bio-based block copolymer poly(6-b-1).