P-V-T relations in a series of longitudinal polymer liquid crystals with varying mesogen concentration

• Published in: Polymer (Guilford) Vol. 39; no. 17; pp. 4081 - 4088
• Main Authors: Berry, James M., Brostow, Witold, Hess, Michael, Jacobs, Elizabeth G.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-08-1998; Elsevier
• Subjects: Applied sciences; Exact sciences and technology; mesogen concentration; Organic polymers; Physicochemistry of polymers; polymer liquid crystal; pressure-volume-temperature; Properties and characterization; Thermal and thermodynamic properties; polymer liquid crystal; pressure-volume-temperature; mesogen concentration; Solid state; Ester copolymer; Molten state; Property composition relationship; Liquid crystal polymers; Thermotropic state; Surface properties; Benzoate(hydroxy) copolymer; Surface tension; Experimental study; PVT relation; Ethylene terephthalate copolymer
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/S0032-3861(97)10388-3

Pressure-volume-temperature (P-V-T) relationships were determined for polymer liquid crystal (PLC) solids and melts up to 400°C and 240 J cm
−3. We have studied a series of longitudinal PLC copolymers with the formula PET/
xPHB, where PET = poly(ethylene terephthalate), PHB = p-hydroxyben-zoic acid (the LC component), with the mole fractions of the LC component 0 ≥
x > 0.8. The P-V-T results are represented by the Hartmann equation of state and its characteristic parameters ν
∗,
T
∗
and P
∗
evaluated. In both solid and liquid phases the
ν
∗(x)
and
T
∗(x)
curves show minima near the concentration
θ
LC limit above which islands of the LC-rich phase are formed. Surface tensions of melts are calculated as a function of
x from the P-V-T data for the liquid state using the theory of Prigogine and Patterson. Increasing
x first causes lowering of the cohesion of the single-phase structure dominated by the flexible PET. Above
θ
LC limit the islands appear to impart their orientation to both phases; this is the channeling effect predicted earlier from the Flory statistical-mechanical theory of PLCs (Blonski
et al., Macromolecules, 1993,
26, 84)