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Van Der, L. H. T. Mee
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article
Oxo-crown-ethers as comonomers for tuning polyester properties
Abstract
2-Oxo-12-crown-4-ether (OC) was procured in a novel, two-step procedure in a 37% overall yield. This interesting hydrophilic lactone was effectively polymd. with Novozym 435 as the catalyst: within 10 min, the monomer conversion was greater than 95%. Poly(2-oxo-12-crown-4-ether) [poly(OC)] was obtained as a viscous oil with a glass-transition temp. of approx. -40 DegC, and it was sol. in water. Subsequently, OC was copolymd. with w-pentadecanolactone (PDL). A kinetic evaluation of both monomers showed that for OC, the Michaelis-Menten const. (KM) and the maximal rate of polymn. (Vmax) were 2.7 mol/L and 0.24 mol/L min, resp., whereas for PDL, KM and Vmax were 0.5 mol/L and 0.09 mol/L min, resp. Although OC polymd. five times faster than PDL, 1H NMR anal. of the copolymers revealed a random copolymer structure. Differential scanning calorimetry traces of the copolymers showed that they were semicryst. and that the melting temp. and melting enthalpy of the copolymers linearly decreased with an increasing amt. of OC. The melting temp. of the copolymers could be adequately predicted by the Baur equation, and this suggested that poly (OC) was rejected from the poly(w-pentadecanolactone) [poly(PDL)] crystals. Solid-state NMR studies confirmed that the cryst. phase exclusively consisted of poly (PDL), whereas the amorphous phase was a mixt. of OC and PDL units.