Polymorphic Crystalline Structure and Properties of Polyamides

Abstract

The polymorphic supermolecular structure of semicrystalline polymers exerts a decisive influence on their macroscopic properties, which is particularly pronounced in polyamide systems dominated by hydrogen bonding. This paper collates the formation mechanisms, regulation strategies and structure-property relationships between polymorphic structures and macroscopic properties of polyamide systems reported in recent years. The regulation methods for the polymorphic crystalline structure of polyamides, based on polymorphism and Brill transition behavior, are categorized into three types: chemical methods involving random copolymerization and block copolymerization; physical methods including polymer blending, nucleating agent incorporation and solution induction; and processing methods such as stretching, shear fields, temperature fields and their coupled fields. The comprehensive properties of polyamides, especially mechanical, thermal, barrier and optical properties, can be effectively tailored via the regulation of their crystalline structures. By systematically reviewing the existing research progress, this review aims to deepen the understanding of the evolution mechanism of polyamide polymorphism and provide novel insights for the development of high-performance polyamide materials.