Definition of stiff chain
Stiff chain refers to a rigid molecular chain that cannot be freely curled to form random clusters in solution. There are basically two types of polymers with a rigid chain structure. Refers to a rod-like polymer chain in which the main chain cannot rotate internally, or that does not change the direction of the chain despite internal rotation; or due to the interaction between groups within the chain (especially hydrogen bonding) The equilibrium state conformation of the molecular chain does not depend on the maximum conformational entropy, but on the maximum interaction energy between the groups within the chain, thereby forming a polymer chain with an α-helix structure, a double-helix structure and an ellipsoidal structure.