Polyamides mixed amide type

Like PU TPE, blends of thermoplastic polyurethanes and polyamide-12 (PA-12) have been studied by Polosmak and co-workers [61]. They have mixed two types of thermoplastic polyurethane (TPU) based on oligoether (polytetramethylene oxide, molecular weight, 1000) and oligoester (polyethylene butylene glycol adipate, molecular weight, 2000) and PA 12 were characterised by IR spectra and thermal analysis. IR spectra of TPU, PA-12 and their blends show that in amide one (Al) carbonyl absorbancy is seen to split [55] into two main bands with maxima at 1705 and 1730 cm 1. At 1730 cm 1,... 

The principal aim of this research was to obtain new types of linear chains rich in amide bonds and along which asymmetric diketopiperazine chromophores are regularly enchained. The CD curves of polymers compared to that of a model compound tend to exclude any interactions among the chromophores along the polymeric chain. Other polyamides based on diketopiperazines of /-glutamic acid or /-aspartic acid by reaction with a variety of diamines have also been investigated [40]. More recently, Cvescenzi et al. [41] prepared mixed polyamide-polyurethane copolymers by reaction of 3,6-bifunctional 2,5-diketopiper-azine with aliphatic and aromatic diisocyanates... 

To identify the most favorable reaction conditions factors such as time, temperature, rate of addition, concentration and solvent composition were investigated f53]. Only low molecular weight polyamides were obtained in the polycondensation of various types of phosphite-amides with dicarboxylic acids (Scheme XXIV). It was also shown that a side reaction like the formation of a mixed anhydride intermediate not only diminishes the yield and molecular weight of the polymer but might contribute also to racemization following Scheme XXIV consequently this method has been abandoned. 

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