Intermediate state and weak intermolecular interactions of α-trans-1,4-Polyisoprene during the gradual cooling crystallization process investigated by In situ FTIR and two-dimensional infrared correlation spectroscopy

The investigation of the gradual cooling crystallization process of alpha-trans-1,4-polyisoprene (alpha-TPI) was carried out for different wavenumber regions by conventional spectral analysis and two-dimensional correlation infrared spectroscopy (2DIR) methods. Interestingly, an intermediate state has been confirmed by the fascinating intensity variation of the 1666 cm(-1) band, and the motion of side-chain (CH3 group) seems to be the initial driving force and precondition for forming the ordered 21 helix conformation. It is also found that the occurrence for the splitting of the CH3 group-related bands is consistent with the appearance of the intermediate state, indicating that the interchain interactions between CH3 groups play an important role in controlling the intermediate state and should be the primary driving force for stabilizing the specific 21 helix conformation.