Influence of host preparation method on the structural phase transitions of syndiotactic polystyrene upon the guest exchange with n-alkanes

The starting morphology used for the preparation of the syndiotactic polystyrene (sPS)/solvent complex, has a significant role in facilitating the phase transitions of the host structure upon guest exchange process. This effect was studied on the structural changes of sPS, using guest exchange process, with a series of n-alkanes, and analyzed by X-ray diffraction and Fourier transform infrared spectroscopy. SPS–solvent complexes (monoclinic δ form) were prepared with different starting morphologies i.e. amorphous, α and γ forms using toluene and chloroform as guests. Upon guest exchange process (performed by dipping the samples in a series of n-alkanes viz. n-octane to n-decane), toluene treated amorphous and α form samples (i.e. monoclinic δ form) transformed into the triclinic δ form irrespective of the starting morphology. However, the toluene treated γ form transformed back to the γ form in presence of n-alkanes. Chloroform treated amorphous sample (i.e. monoclinic δ form), however, converted to a mixture of δ form (triclinic) and ε form, while chloroform treated α and γ forms transformed into triclinic δ form and ε form, respectively. Besides host preparation method, influence of starting δ form crystallinity on the guest exchange process was also examined.