Analysis of the Spherulitic Growth Rate of Poly(Pivalolactone) in Blends with Poly(Vinylidene Fluoride)

Abstract

Using polarized optical microscopy, we have studied the temperature dependence of the α-phase poly(pivalolactone) (PPVL) spherulite growth rate in blends with poly(vinylidene fluoride) (PVF2) for compositions ranging from pure PPVL to 10/90 wt/wt PPVL/PVF2. Using the Lauritzen-Hoffman crystal growth model, we have determined the variation in equilibrium melting temperature of a-phase PPVL with blend composition directly from the spherulitic growth rate data. The predicted depression in equilibrium melting temperature was successfully analyzed following the treatment proposed by Nishi & Wang and based on Scott’s expression for chemical potentials in a binary polymer mixture to yield a negative interaction parameter (χ = — 0.13). Analysis of the composition dependence of the nucleation constant, Kg, suggests that the PPVL crystal/melt lateral interfacial free energy, σ, decreases markedly with increasing PVF2 concentration in the blend. Such an observation is discussed on the basis of a recent model for the crystal/melt lateral interfacial free energy.