Chain Multiplication of Fatty Acids to Precise Telechelic Polyethylene

Starting from common monounsaturated fatty acids, a strategy is revealed that provides ultra-long aliphatic α,ω-difunctional building blocks by a sequence of two scalable catalytic steps that virtually double the chain length of the starting materials. The central double bond of the α,ω-dicarboxylic fatty acid self-metathesis products is shifted selectively to the statistically much-disfavored α,β-position in a catalytic dynamic isomerizing crystallization approach. "Chain doubling" by a subsequent catalytic olefin metathesis step, which overcomes the low reactivity of this substrates by using waste internal olefins as recyclable co-reagents, yields ultra-long-chain α,ω-difunctional building blocks of a precise chain length, as demonstrated up to a C₄₈ chain. The unique nature of these structures is reflected by unrivaled melting points (T_m =120 °C) of aliphatic polyesters generated from these telechelic monomers, and by their self-assembly to polyethylene-like single crystals.