Aliphatic polyesters as models for relaxation processes in crystalline polymers: 1. Characterization

Syntheses and characterization of poly(pentamethylene pimelate), poly(1,6 hexamethylene adipate), poly(1,6 hexamethylene sebacate) and poly(2,5 hexamethylene adipate) are described. The first three are semicrystalline and the last completely amorphous. Dilatometry is used to establish volume-temperature curves (in both the solid and liquid regions in the first three). Liquid densities at 25°C are respectively 1104, 1096, 1033 and 1076 kg m^?3. Powder and fibre X-ray diffraction patterns on poly(pentamethylene pimelate) and poly(hexamethylene adipate) are indexed as monoclinic (a = 0.614, b = 0.737, c = 1.716 nm, β = 54.6°) and orthorhombic (a = 1.008, b = 0.732, c = 0.1683 nm), respectively. Under the assumption of 2 and 4 chains/cell, respectively, these lead to crystal densities of 1198 and 1222 kg m^?3, respectively, for these two polymers. The density of poly(1,6 hexamethylene sebacate) is known from the literature. Differential scanning calorimetry is used to establish crystal heats of fusion for the first three polymers as 151, 151, and 134 kJ kg^?1, respectively. The melting and crystallization temperatures of poly(1,6-hexamethylene adipate) are measured as a function of pressure up to 275 MPa. The heat of fusion derived from these data and the density data using the Clausius-Clapeyron equation is 167 kJ kg^?1.