Abstract: An unambiguous assignment of the main ¹H NMR resonance of nylon 6 in trifluoroacetic acid (TFA) solution was carried out by using a combination of 1D and 2D NMR heteronuclear technique (HMQC). The spin-spin relaxation time measurements at different temperatures provide the information about cohesional entanglements of main chains among the macromolecules and the dynamics of nylon 6 polymer at different temperatures in TFA solution. The results show that the methylene groups of the nylon 6 main chains are cohesionally entangled in different degrees at the ambient temperature. The farther the methylene group from the CO and NH groups,the more intensely entangled they are. The entanglements of the methylene groups adjacent to the CO and NH groups,are less pronounced owning to the formation of interchain hydrogen bonds. These entanglements are gradually weakened by the thermal motion upon increasing temperature. The absence of the variation in t 2H of the NH proton with the charge of temperature and the decrease in t 2H of the TFA protons with the increase in temperature give an evidence about the dissociation of the interchain hydrogen bonds among the nylon 6 molecules and the formation of hydrogen bonds between TFA protons with the NH and CO groups of nylon 6 set free by increasing temperature.

Key words: Cohesional entanglement, NMR, Relaxation time, Nylon 6, Hydrogen bond