Abstract
Recent thermodynamic studies of crystalline p-polyphenyls are described. The properties of the twist transitions of biphenyl, p-terphenyl and p-quaterphenyl are discussed in relation to the internal flexibility. The crossover of the low temperature heat capacities of biphenyl and p-terphenyl is attributed to the greater twisting flexibility of biphenyl molecule on the basis of lattice dynamics calculations. The role of the incommensurability is discussed about the abnormally large heat capacities of biphenyl at low temperatures. The thermodynamic properties are also discussed of other related substances (4, 4'-difluorobiphenyl, p, p'-biphenol, perfluorobiphenyl and perchlorobiphenyl).
