Synthesis and properties of segmented copolymers having aramid units of uniform length

Segmented copolymers consisting of crystallizable p-phenyleneterephthalamide ester units and poly(tetramethyleneoxide) segments were synthesized. The synthesis of the p-phenyleneterephthalamide ester starting material was optimized with respect to yield and purity. The polymers were synthesized via a solution/melt polymerization. The possibilities for a melt polymerization are also discussed. The length of the poly(tetramethyleneoxide) segment in the polymers was varied from 650 to 2900 g/mol. Also other types of low Tg segments were incorporated in the polymers: modified poly(tetramethyleneoxide) (methyl side groups), poly(oxyethyleneglycol) and poly(ethylene/butylene). The polymer properties were investigated with differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The polymers are fast crystallizing and the p-phenyleneterephthalamide units crystallize nearly completely. As a result the glass transition is sharp and low (−65°C), the rubbery plateau is temperature independent and the flow temperature is high. Polymers with poly(oxyethyleneglycol) have a high water uptake. Polymers with poly(ethylene/butylene) segments already phase separate during the polymerization inhibiting the formation of high molecular weight polymers.