First-Order Transition Temperatures in Crystalline Polymers

The concept of lamellar, crystalline polymers with molecular ends and comonomer components included in the crystal lattice as defects has been used to derive a relationship between first-order transition temperature, comonomer content, molecular weight, and lamellar thickness. The relationship is reduced to equations for three special cases, which describe the variation of transition temperature with comonomer content, molecular weight, and lamellar thickness, respectively. These equations have the same functional relationship as those obtained previously using the concept of perfect (homopolymer) crystals from which molecular ends and comonomers are excluded. Additionally, if certain constant terms have the appropriate values, the present equations are identical with the earlier ones. These constants measure the difference between the defect regions and the perfect lattice. The constants imply that the transition temperature should vary with the type of comonomer of molecular end as well as with the comonomer content or molecular weight.