Abstract
The combination of polymer and metal salt opens manifold possibility in practical uses for enhanced electrical and mechanical properties. Furthermore, through in situ reduction of metal salts in the hybrids, metal nanoparticles (NPs) can be formed and incorporated properly into the polymer matrix. In this thesis, we systematically discussed how the reduction condition of a palladium salt dissolved in a polymer matrix influenced the ultimate morphology of the resultant palladium NPs in the hybrids. In addition, we revealed the impact of lithium salt on the microphase separation behavior of a block copolymer exhibiting lower critical ordering transition (LCOT) behavior and a unique effect in inducing large-scaled microdomain orientation in the block copolymer. For the first part of the work, we prepared Pd NPs through in situ reduction of palladium acetylacetonate (Pd(acac)2) dissolved in poly(2-vinylpridine) (P2VP). The reduction reaction occurred through thermal decomposition of Pd(acac)2, which was exothermic and usually took place above 150 oC in P2VP matrix. We examined the effects of reduction temperature (Tred), concentration of Pd(acac)2 precursor and molecular weight of P2VP on the dispersion morphology of the Pd NPs in the nanocomposites by small angle X ray scattering (SAXS). At lower Tred (e.g. 150 oC), the nanocomposites were found to compose of spherical Pd NPs which distributed uniformly in the matrix. The Pd NPs underwent aggregation to form local clusters which further agglomerated to construct a large-scale fractal structure at higher Tred. Generally, the size and the local number density of Pd NPs became larger at higher Tred. Increasing P2VP molecular weight tended to reduce the NP size. In the second part, we chose poly(ethylene oxide)-block-poly(4-vinylpyridine) (PEO-b-P4VP) as a template to host lithium perchlorate (LiClO4) to study the morphology of PEO-b-P4VP during thermal annealing process. The hybrids were characterized by temperature-dependent FTIR spectroscopy to show that Li+ ions were selectively solvated in EO domains at low salt concentration. Li+ ions gradually interacted with 4VP with increasing salt content but they dissociated from the binding with 4VP at the higher temperature. Through the use of temperature-dependent SAXS, we found that Li+ ions can serve as anchors to fix the junction points at the interface between EO and 4VP domains and hence induced large-scaled orientation in the bulk during thermal annealing process. Besides, disorder-to-order transition temperature was suppressed due to the stronger segregation power caused by lithium salt.