Polyether-amide segmented copolymers based on ethylene terephthalamide units of uniform length

Segmented copolymers were synthesized using the crystallizable bisesterdiamide segment (N,N'-bis(p-carbomethoxybenzoyl)ethanediamine) T2T-dimethyl (a one-and-a-half repeating unit of nylon 2,T) and poly(tetramethyleneoxide) segments. Poly(tetramethyleneoxide) (PTMO) is amorphous and has a low T-g. The segment length was varied from 650 to 2800 g/mol by extending PTMO650 using dimethyl isophthalate. The polymers were synthesized in the melt, and test samples were prepared by injection molding. The melting behavior, as well as the torsion modulus spectrum as a function of temperature, were studied using DSC and DMA, respectively. The T2T-PTMO polymers were found to have sharp glass (T-g) and flow transitions (T-fl), and the modulus at the rubbery plateau appeared to be virtually temperature independent. The T-g value was found to be independent of the diamide concentration, thus indicating that the T2T segments were fully crystallized. The T-fl was found to decrease with increasing soft segment length; this was ascribed to a "solvent" effect of the amorphous phase of the crystalline T2T units. The difference between the melting and crystallization temperatures was found to be low, thus suggesting that on cooling, there is a high rate of crystallization. When ethanediol was added as a T2T segment extender, amide-ester-amide segments were introduced. These amide-ester-amide segments form a separate lamellar phase with a much higher melting temperature (>300 degreesC). It was found that the crystallization rate of the T2T units was enhanced by the presence of the amide-ester-amide segments, indicating that upon cooling, the crystallized amide-ester-amide segments form the nucleation sites for the nonextended T2T segments. (C) 2001 John Wiley & Sons, Inc.