Polymeric triglyceride analogs prepared by enzyme-catalyzed condensation polymerization

Unique crosslinkable unsaturated polyesters were prepared by a one-pot lipase-catalyzed copolymerization of crude linoleic acid (LA), glycerol (G) and 1,18-cis-9-octanedecenedioic acid (oleic diacid, OD). The lipase used is Candida antarctica Lipase B (CALB) immobilized on Lewatit (N435). Experiments were conducted to assess N435’s efficiency of forming poly(OD-co-G-co-LA) as a function of: (i) LA content in the co-monomer feed and (ii) reaction time. For comonomer feed ratio (OD:G:LA) 1:1:0.67, Mn reached ∼9500 in 8 h, trisubstituted G-units increased to 64% and monomer was largely depleted. When LA and OD remained in products, a lower temperature thermal decomposition peak at about 280 °C was observed in addition to a higher temperature decomposition peak at ∼475 °C. By increasing LA content in the comonomer feed from 1:1:1 to 1:1:1.33, Mn decreased from 11,000 to 6300 while trisubstituted G-units increased from 92 to nearly 100%. Thus, by varying the feed ratio of LA, polymeric triglyceride-type structures were formed with control of chain length and trisubstituted G-unit content. Since G-units may be substituted in various ways with OD and LA, calculations were performed that determined the relative proportion of different substitution patterns in products. A hypothetical structure showing general characteristics of the substitution at glycerol units for one such product is presented.