The heat capacity of crystalline p-quinquephenyl was measured
by adiabatic calorimetry below room temperature.
A broad hump was detected around 264 K
and attributed to a phase transition,
through which an average molecular conformation changes
from the planar to the twisted one on cooling.
A similar anomaly was also detected for crystalline p-sexiphenyl
around 295 K by chopped-light ac calorimetry.
The broad shape of the thermal anomalies arising from
the twist transitions are discussed
in relation to the number of possible intramolecular twisting modes.
Properties of the twist transition in polymer are discussed
on the basis of those of oligomers.
Standard thermodynamic functions are tabulated for p-quinquephenyl.
(Bull. Chem. Soc. Jpn., 73, 2713-2718 (2000))
The heat capacity of crystalline poly(p-phenylenebenzobisoxazole)
was measured below room temperature by adiabatic calorimetry.
The standard thermodynamic functions (enthalpy, entropy and Gibbs energy)
were established and tabulated.
the temperature dependence of the heat capacity was compared with
those of polyethylene and poly(p-phenylene),
with attention paid to the low dimensionality of the systems.
(J. Polym. Sci.: Part B: Polym. Phys., 38, 1584-1588 (2000))
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