Thermodynamic properties in the liquid state of high melting polymers containing phenylene and naphthylene groups

Abstract

Abstract High melting polymers of three different types of crystallization behavior were analyzed as to their thermal properties. The heat capacity at constant pressure of liquid poly(butylene terephthalate) (PBT) from 490 to 540 K was measured by scanning calorimetry. Combining with prior measured liquid heat capacity data of poly(oxy‐1,4‐phenylene) (PO) (358 – 620 K), poly‐(thio‐1,4‐phenylene) (PPS) (540 – 600 K), poly(ethylene 2,6‐naphthalenedicarboxylate) (PEN) (400 – 450 K, 530 – 600 K), an addition scheme for liquid heat capacities was constructed. In addition, the thermodynamic functions H and S have been calculated for those five polymers. The absolute, molar, residual entropy for the glassy state at zero kelvin is estimated to be 6,6,15,2, 7,48, 5,70, and 19,9 J/(K · mol) for PPS, PEN, PPO, PO, and PBT, respectively. Another two polymers with similar structure, poly(1,4‐oxybenzoic acid) (POB) and poly(2,6‐oxynaphthoic acid) (PON), were also studied in their high temperature mesophase states. A test of the addition scheme has been made to predict their heat capacities.