Enzyme-catalyzed polymerizations at higher temperatures: Synthetic methods to produce polyamides and new poly(amide-co-ester)s

摘要

Novozyme-435 (N-435) catalyzed polycondensation reaction between different aliphatic (oligo)esters and diamines by precipitation polymerization at elevated temperatures yields various particulate polyamides and poly(amide-co-ester)s. The reaction between diethylsebacate (DES) and 1,8-diaminooctane (DAO) at 60°C in dried toluene leads to a low M_n polyamide (NMR: M_n = 520gmol~(_1) GPC: M_n = 2000g mol~(-1)with M_w/M_n = 1.3). An improved three-step procedure with an adjusted temperature profile and an optimized amount of enzyme in dried diphenyl ether, yields 97% amide bond formation and a polymer with increased molecular mass (NMR: M_n = 5380 g mol~(_1), GPC: M_n=4960gmol~(-1) with M_w/M_n =3.5). Three step ring-opening and polycondensation reactions between a cyclic ester (ethylene tridecanedioate) with three different diamines were also performed in dried toluene to obtain the corresponding polyamides. Here, diamine with higher alkyl chain length, i.e. 1,12-diaminododecane shows higher activity towards N-435 catalyzed amide bond formation and therefore the produced nylon-12,13 has higher molecular weight (GPC: M_n=8250g mol~(-1) and M_w/M_n = 5.8) compared to the other nylons. By adopting the three step synthetic protocol, a new series of poly(amide-co-ester)s with M_n up to 17,550gmol~(-1) were produced. Melting and thermal degradation behaviors of these copolymers are compared with pure nylon-8,10 and polyester by DSC and TGA. The microstructure of the synthesized polyamides with different end groups was investigated by MALDI-TOF MS analysis while the particles' morphology was studied by TEM analysis.