The phase transitions of lithium perchlorate (LiClO4)- doped polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) were studied as a function of temperature and ion salt concentration using in situ small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Incorporation of LiClO4 into an asymmetric, disordered PS-b-P2VP copolymer produced temperature-dependent order–disorder (ODT) and order–order transitions (OOTs) from spherical to lamellar microphases. The effective interaction parameter (χeff) between two block components was evaluated for low molecular weight LiClO4-doped PS-b-P2VP in a disordered state. With increasing quantities of LiClO4, a remarkable increase in χ along with a volumetric change produced by the selective coordination of LiClO4 to the ionophilic P2VP block led to morphological transitions from disordered (DIS) to body-centered cubic spherical (BCC) to hexagonally packed cylindrical (HEX) to lamellar (LAM) structures. We also demonstrate that the ionic conductivity in the samples quenched from the different structures is morphology-independent, while it increases with increasing salt concentration.
We present experimental results for the glass transition behavior of polystyrene (PS) films on grafted PS layers of the same chemical identity as a function of film thickness. Our results suggest that the T g of PS films on brush substrates decreases with decreasing film thickness. The thickness dependence of T g was observed to be more pronounced for the films on the shorter brushes with the high grafting density. We propose a qualitative rationalization of the observations by invoking both interfacial energy considerations as well as by adapting the percolation model for the glass transition of polymer films.
The variations of impact strength and compressive strength of unsaturated polyester based sisal/glass hybrid composites with fiber loading have been studied. The impact strength of these hybrid composites has been found to be higher than that of the matrix, whereas a marginal decrease was observed in the compressive strength of the hybrid composites over that of the matrix. The effects of NaOH treatment and trimethoxy silane (coupling agent) treatment on the impact and compressive properties of these sisal/glass hybrid composites have also been studied. No significant improvement in impact strength of the sisal/glass hybrid composites has been observed by these treatments, whereas a marginal increase in compressive strength of these hybrid composites has been observed.
The variation of tensile strength of unsaturated polyester based sisal-glass hybrid composites with fiber loading has been studied. The tensile strength of these hybrid composites has been found to be higher than that of the matrix. The effects of NaOH treatment and trimethoxy silane (coupling agent) treatment on the tensile properties of these sisal-glass hybrid composites have also been studied. Significant improvement in tensile strength of the sisal-glass hybrid composites has been observed by these treatments.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.