Understanding the viscosity decline of poly(amic acid) solution from the correlation point of view

POLYMER

卷:202

Article

Zhang, Huan¹  Gao, Yangyang²  Han, Charles C.³ 

[1] Aerosp Res Inst Mat & Proc Technol, Beijing 100076, Peoples R China

[2] Beijing Univ Chem Technol, Key Lab Beijing City Preparat & Proc Novel Polyme, Beijing 10029, Peoples R China

[3] Chinese Acad Sci, Inst Chem, Beijing Natl Lab Mol Sci, Beijing 100190, Peoples R China

关键词: Poly(amic acid);    Light scattering;    Relaxation;   

DOI  :  10.1016/j.polymer.2020.122728

来源: Elsevier

【 摘 要 】

The effects of storage time and temperature on the properties of poly(amic acid) (PAA) solution were reexamined by dynamic and static light scattering. One fast and one slow relaxation modes were observed in fresh prepared semidilute solution. The fast mode corresponds to cooperative diffusion of chain segments inside each blob while the slow mode comes from the long-range correlated concentration fluctuation of transient network. Chains relaxation during storage at room temperature (20 degrees C) leads to the disentanglement of transient network and viscosity drop, thereby only one fast relaxation mode was observed which was related to the mutual diffusion of separated polymer chains. Cooling (to 2 degrees C) rejuvenates the solution to a certain extent, by which the slow relaxation mode can be regenerated and viscosity re-rises. These results indicate that PAA solutions experience a slow thermodynamic and kinetic transition during storage. Hydrolysis may not be the only reason responsible for the viscosity decrease of the PAA solution, the arrangement of chain conformation during storage should be accounted for.

【 授权许可】

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