THERMOVOLUMETRIC PROPERTIES VERSUS GLASS-TRANSITION TEMPERATURE OF DIOLIC PERFLUORO-POLY-(OXYETHYLENE-RAN-OXYMETHYLENE) OLIGOMERS

The specific volume upsilon from -20 to 60 degrees C and the glass transition temperature T-g was measured of a homologous series of linear diolic oligomer fractions constituted by a random perfluoro-poly(oxyethylene-ran-oxymethylene) chain of fairly uniform composition and two -CH2OH end units, with a degree of polymerization ($) over bar x(n) from 5,4 to 165,9 (($) over bar M(n) from 400 to 14900). An empirical parabolic upsilon = upsilon(T, w(E)) equation of state is found as satisfactory, w(E) being the end copolymeric composition expressed as weight fraction of end units, inversely proportional to ($) over bar M(n). A predictive bridge is then established between thermovolumetric parameters and T-g, through a highly reliable linear relation upsilon(g)-T-g between experimental T-g and calculated specific volume at T-g, which leads with measurable parameters to a T-g-w(E) relation, in very good agreement with experimental results. For the range of ($) over bar M(n) above 1 500-2 000, simpler relations can also be used to a good approximation, which are discussed in their physical meaning and validity.