Block copolyetheresters. V. Low-temperature properties of thermotropic block copolyetheresters

The low-temperature properties of block copolyetheresters with hard segments of poly(alkylene p,p′-bibenzoate) and soft segments of poly(tetramethylene ether) were investigated by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). In the temperature range of −100 to 60°C, two transition temperatures, a glass transition temperature (T_g) and a melting temperature (T_m), were found by DSC and are attributed to the polyether segments. The T_g monitored by DSC of the polyether segments of the block copolyetheresters is around −68°C and independent of the composition and the type of polyester segment. Thus, the amorphous parts of the polyether segments should be immiscible with the amorphous parts of the polyester segments. The polyether segments of the block copolyetheresters exhibit a lower T_m and a lower crystallinity than those of the poly(tetramethylene ether)glycol due to the presence of the polyester segments. The crystallizability of the polyether segments is dependent on the composition to some extent. The DMA data show that the dynamic modulus drops more abruptly around −10 to 15°C, indicating that the mechanical properties may change significantly due to the melting of the polyether segments. © 1996 John Wiley & Sons, Inc.