Reflection-absorption infrared spectroscopy study of polyacrylonitrile on copper at elevated temperature

Reflection-absorption infrared spectroscopy (PAIR) has been used to investigate the chemical structural changes in Polyacrylonitrile (PAN) film adsorbed on copper at 200 degrees C for different time. The formation of an almost fully conjugated C-C=C backbone occurs after heating for only 2 h due to the catalytic effect of copper. The freely dangling cyano groups in PAN molecules initially coordinate to copper surface through the triple bond in pi-bonded orientation, then convert to sigma-bonding through the donation of the lone pair of electrons of nitrogen. It is suggested that this transition of the types of coordination would relate to the different geometries of PAN on copper during heating. Since the nitrile complexing and cyclization occur at the same time, the reaction process for the pyrolysis of PAN on copper surface is different from that in the bulk.