Factors controlling the structure of syndiotactic polystyrene upon the guest exchange and guest extraction processes

Abstract

The role of host preparation method on the structural phase transition of syndiotactic polystyrene (sPS)after the guest exchange process has been thoroughly investigated in our previous study using a series of n-alkanes [Polymer 2013; 54:6617-27]. In addition to the host preparation method, we have found that guest molecules used for the guest exchange process also have a significant role in facilitating the phase transitions of the host structure. Chloroform and toluene treated gamma form samples were used as starting materials for the guest exchange process with different kind of solvents. Solvents that are capable of crystallizing sPS into the delta (d) co-crystal are termed as clathrate guests and the solvents which are crystallizing sPS directly into the gamma form are termed as gamma form inducing solvents. Upon guest exchange process (performed by dipping the samples in clathrate guests and gamma form inducing solvents), chloroform treated of g form (ε clathrate) sample transformed into the mixture of ε clathrate and d clathrate in the presence of clathrate guests, whereas the ε co-crystal is retained its structure in the presence of gamma form inducing solvents. However, the toluene treated gamma form (monoclinic d) samples show different structures upon guest exchange process depending on the kind of guest molecules. In the case of clathrate guests, upon the guest exchange, the monoclinic d retained its structure; however, the toluene treated gamma form (monoclinic d) transformed to the gamma form in the presence of gamma form inducing solvents. Apart from the guest exchange process, structural changes upon the guest extraction process were also investigated.