Power law and scaling for molecular weight dependence of crystal growth rate in polymeric materials

The molecular weight (M) dependence of the linear crystal growth rate (G) and the influence of the super-cooling on the relationship between M and G were studied. The molecular weight dependence of G has been expressed generally as G∝M^α at a given super-cooling. The temperature dependence of G shows a bell shape with the maximum growth rate (G_max). The value of α was −0.5 at the temperature (T_cmax) of G_max. However, the small super-cooling and the small molecular weight gave a large negative value of α. In other words, the value of α was dependent not only on the degree of super-cooling (ΔT) but also on the molecular weight. The effect on α by these two factors (ΔT and M) goes off to zero at T_cmax and α yields to −0.5. G_max can be defined as a characteristic intrinsic value to the crystal growth behavior. The molecular weight dependence of G_max was scaled and expressed as a −0.5 power to molecular weight for all crystalline polymers.