Enzymatic synthesis and solid-state properties of aliphatic polyesteramides with polydimethylsiloxane blocks

The synthesis of silicone polyesteramides was successfully performed in bulk at 70 °C via a biocatalytic route. Immobilized Candida antartica Lipase B (Novozyme 435, N435) was used as catalyst under mild conditions to perform the polycondensation reaction using various feed mole ratios of diethyladipate (DEA), 1,8-octanediol (OD) and alfa,omega-diaminopropyl-polydimethylsiloxane (Si-NH2). The syntheses of poly(octamethylene adipate), POA, and poly(alfa,omega-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 1H NMR spectroscopy, and calculated amide/ester ratios were in agreement with the monomer feed mole ratio. Thermal stability of the polyesteramides, evaluated by TGA both in nitrogen and in air, increases with polydimethylsiloxane adipamide content (up to 50mol%). The relative amount of amide and ester units along the polymer chain strongly affects the physical aspect of the polyesteramides. High content of octamethylene adipate units leads to hard solid materials containing a well developed high melting POA-type crystal phase, whose melting temperature changes with composition. When polydimethylsiloxane adipamide is the major component, the material acquires a sticky appearance.