Effect of molecular weight on spherulite growth rates of high molecular weight poly(ethylene oxide) fractions

Spherulite growth rates have been determined for a set of poly(ethylene oxide) fractions ranging in molecular weight from 10⁴ to 10⁶. At a given crystallization temperature the spherulite growth rate as a function of molecular weight passes through a maximum. At a given undercooling (as assessed by the method of Mandelkern) the spherulite growth rate is a monotonically decreasing function of molecular weight, and in the range $\text{6000 <}\text{M}\text{?}{}_{\mathrm{v}}\text{< 50 000}$ varies roughly as $\text{(}\text{M}\text{?}{}_{\mathrm{v}}\text{)}{}^{\mathrm{?3}}$. The free energy of formation of the end interface (as assessed by nucleation theory) also decreases as molecular weight increases.