K. Cheuk, J. Lam, Junwu Chen
Jul 15, 2003
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Macromolecules
Abstract
l-Leucine−phenylacetylene adducts 6 and 14 undergo self-association in concentrated solutions and heterocomplexation with solvent molecules through hydrogen bond formation. The adducts are polymerized by rhodium catalysts into poly(4-ethynylbenzoyl-l-leucine methyl ester) (1e) and poly[11-(4-ethynylphenoxy)undecanoyl-l-leucine methyl ester] (2e), with the polymerizations of 6 producing polymers with high molecular weights (Mw up to 1.47 × 106) and high stereoregularity (Z content up to 100%) in high yields (up to 92%). The ester groups of “polyesters” 1e and 2e are selectively hydrolyzed under basic conditions to afford “polyacids” 1a and 2a carrying free leucine pendants. The polymers are thermally stable (up to ∼260 °C) and undergo Z−E isomerization at ∼200 °C. The chirality transcription from the l-leucine pendants induces the chain segments of polymers 1 to helically spiral predominantly in one preferred direction, while the helicity induction processes in 2 are interrupted by the relaxations of the l...