Open AccessEffect of ambient atmosphere on the formation and evolution of conjugated structure of pre-oxidized polyacrylonitrile
Author(s) -
Bin Wang,
Lei Shuai,
Chenggao Li,
Aijun Gao
Publication year - 2022
Publication title -
materials research express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.383
H-Index - 35
ISSN - 2053-1591
DOI - 10.1088/2053-1591/ac6aba
Subject(s) - conjugated system , polyacrylonitrile , photochemistry , chemical structure , chemistry , conjugate , fourier transform infrared spectroscopy , double bond , infrared spectroscopy , materials science , organic chemistry , polymer chemistry , polymer , chemical engineering , mathematical analysis , mathematics , engineering
The ambient atmosphere has the remarkable effect on the chemical reaction mechanism and the formation of characteristic chemical structures and conjugated structures for pre-oxidized PAN. In the present paper, fourier transform infrared spectroscopy (FT-IR) and ultraviolet visible spectroscopy (UV-vis) were used to characterize the variations of chemical reaction characteristic structures and conjugate structures of copolymerized PAN in nitrogen and air atmosphere, respectively. Combined with the multivariate reaction model proposed by the predecessors, it can be found thatthat two main conjugated structures (conjugated polyene and conjugated aromatic heterocycle) formed during the pre-oxidation process of copolymerized PAN . In nitrogen atmosphere, the formed main structure units were the conjugated diene and conjugated double ring with 1-2 double bonds. By contrast, the formed main units in air were the conjugated diene and conjugated tricyclic with a double bond. During the whole pre-oxidation process, the maximum unit numbers of conjugated double bonds and conjugated rings were no more than four and six, respectively. Increasing the heat treatment temperature was easy to form more conjugate structures than prolonging the heat treatment time. Furthermore, with the increase of heat treatment temperature or time in air, the main conjugate unit numbers had no obvious change, while the maximum unit numbers increased slightly. When exposed in nitrogen atmosphere , the main conjugated polycyclic structure was transformed into conjugated tricyclic structure after the heat treatment at 250 oC for more than 3 hours. In addition, when the heat treatment temperature and time were 280 oC for more than 4 hours, the main conjugated polyene structure was transformed into conjugated triene, andthe maximum conjugated unit numbers increased slightly with it.