Spherulitic Growth of Poly(ethylene oxide) from Viscous Solution

Abstract

Spherulitic growth of poly(ethylene oxide) from 30 wt% tripropionin (glycerol tri-n-propionate) solution was investigated in the supercooling range ΔT=11–37 K. The solution was pre-annealed at 200°C before isothermal crystallization. The estimated total crystallization rate decreases with increasing pre-annealing time, and becomes almost constant with a pre-annealing time longer than ca. 200 h. This suggests that traces of crystalline nucleus remaining in the solution dissolve during the pre-annealing process. The isothermal crystallization rate G with respect to the crystallization temperature was measured using isothermal calorimetric measurements and direct observation of the spherulitic growth using a CCD camera. The Avrami exponent estimated from the isothermal crystallization data ranges from ca. 2.7 to 3.2 depending on the crystallization temperature. The profile of G vs. T was also analyzed to estimate the parameters for the diffusion factor, and the result shows that the diffusion process belongs to the low friction limit, i.e., frictional interaction between the polymer and solvent is extremely weak.