Size‐Dependent Melting Temperature of Polymers

A general model for all kinds of size‐dependent melting points, free of any adjustable parameter, is extended to illustrate the size‐dependence of the melting temperature of polyethylene (PE). The model prediction for the depression of the melting temperature of PE is consistent with the calorimetric experimental results as shown in the Figure where the melting temperature of lamellae PE crystals as a function of the thickness of the crystals is presented.

The T_m(D) function of PE shown as a solid line in terms of Equation (4). The necessary parameters for use of Equation (4) are shown in Table 1. The symbols ○ and • denote the experimental evidence of T_m(D) of linear alkanes14b and cyclic alkanes,14c respectively. The values of D are determined by D = 0.1273n6 with 0.1273 nm being the orthorhombic CC lattice distance in the c‐direction.5 The symbol □ denotes the experimental evidence of chain‐extended PE.6