Enzymatic Synthesis and Solid-State Properties of Aliphatic Polyesteramides with Polydimethylsiloxane Blocks

Abstract

The synthesis of silicone polyesteramides was successfully performed in bulk at 70 °C via a biocatalytic route. Immobilized Candida antartica Lipase B (Novozym 435, N435) was used as catalyst under mild conditions to perform the polycondensation reaction using various feed mole ratios of diethyl adipate (DEA), 1,8-octanediol (OD), and α,ω-(diaminopropyl)polydimethylsiloxane (Si-NH 2 ). The syntheses of poly(octamethylene adipate), POA, and poly(α,ω-(diaminopropyl)polydimethylsiloxane adipamide), PSiAA, were also performed by N435 catalysis in order to compare their properties with those of silicone polyesteramides. The microstructures of all polymers were studied by 1 H NMR spectroscopy, and calculated amide/ester ratios were in agreement with the monomer feed mole ratio. Formation of amide links (DEA−SiAA units) occurs more rapidly than ester repeats (DEA−OA units). This results in copolymers that tend toward a blocklike sequence distribution. Thermal stability of the polyesteramides, evaluated by TGA both in nitrogen and in air, increases with DEA−SiAA content (up to 50 mol %). The relative amount of amide and ester units along the polymer chain strongly affects the physical aspect of the polyesteramides. High content of DEA−OA units leads to hard solid materials containing a well-developed high melting POA-type crystal phase, whose melting temperature changes with composition. When DEA−SiAA units are the major component, the material acquires a sticky appearance.