Multistep structure evolution during the coagulation of PAN/DMSO solution studied by in-situ FTIR spectroscopy

Abstract

Coagulation is the first step in the formation of the aggregation structure during the preparation of polyacrylonitrile (PAN) fiber, which has a significant effect on the mechanical properties of PAN precursor and its based carbon fiber. However, due to the rapid coagulation speed of the PAN/DMSO solution in the coagulation bath , research about the complex matter exchange and structural evolution during this process is still a challenging topic. In the present study, the PAN/DMSO solution was set in an environment with constant humidity to slow down the coagulation rate. In situ FTIR measurements combined with two-dimensional correlation analysis were used for the first time to study the detailed evolution of the intermolecular interaction and PAN chain conformation caused by the change of H 2 O, DMSO , and PAN content during coagulation. The results indicated that with the diffusion of H 2 O from the atmosphere to PAN/DMSO solution, hydrogen bonds between H 2 O and DMSO were gradually generated, which led to a chemical environmental change around PAN chains and promoted the dissociation of PAN and DMSO. After that, the parallel-oriented –CN groups promoted the conformation change of the PAN chains.