A series of novel hyperbranched hydrogen-bond acidic polymers for surface acoustic wave (SAW) sensor applications were prepared by functionalizing hyperbranched polycarbosiloxanes or polycarbosilanes with phenol or hexafluoro-2-propanol groups. Starting polymer, sensor polymer, and reagent structures were confirmed by IR, 1 H, 13 C, and 29 Si NMR, SEC, or GCMS as appropriate. The hyperbranched sensor polymers were coated onto 500 MHz SAW platforms and their responses to the nerve agent simulant dimethyl methylphosphonate (DMMP) were studied. The hyperbranched sensor polymers with phenol groups gave very high initial responses to DMMP which dropped to 30% of the initial levels over a period of 6 months, and the hyperbranched sensor polymers with hexafluoro-2-propanol groups gave lower initial responses that did not change with time. Hence, the long-term performances of hyperbranched phenolic sensor polymers and hyperbranched hexafluoro-2-propanol sensor polymers were found to be comparable.

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Three novel polyhedral oligosilsesquioxane (POSS) nanofillers functionalized with proton-conducting sulfonic acid groups, mixed sulfonic acid and alkyl groups, and phosphonic acid groups were synthesized, characterized by IR, 1 H and 13 C NMR, and MALDI-TOF MS, and formulated into sulfonated polyphenylsulfone (S-PPSU) carrier polymers. High quality films were cast from 1-methyl-2-pyrrolidinone (NMP), and through-plane and in-plane proton conductivity, mechanical properties, water uptake, dimensional stability, and leaching behavior were measured to assess their suitability for use as hydrogen fuel cell proton exchange membranes. Various nanofiller loadings and S-PPSU sulfonation levels were studied. The morphologies of the composite membranes were determined by TEM and SEM X-ray mapping. When compared with Nafion 1 , the POSS-S-PPSU composite membranes exhibited comparable proton conductivity in combination with superior dimensional stability, heat resistance, and mechanical strength. When compared with control S-PPSU membranes, the composite POSS-S-PPSU membranes exhibited superior conductivity, comparable dimensional stability, and slightly decreased mechanical strength.

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Three series of hyperbranched polycarbosiloxanes (HB-PCSOX) and polysiloxanes (HB-PSOX) were prepared from octafunctional polyhedral oligomeric silsesquioxane (POSS) monomers and various difunctional silanes by bimolecular nonlinear A8-B2 polymerization (BMNLP) and characterized by IR, 1H NMR, 29Si NMR, SEC, DSC, and for refractive index. Series 1 was prepared from T8vinyl8 and disilane monomers, and series 2 was prepared from T8(OSiMe2H)8 and divinylsilane monomers (where T denotes an SiO3 unit), both via platinum-catalyzed hydrosilylation polymerization. Series 3 was prepared from T8(OSiMe2OH)8 and dichlorosilane monomers via hydrolysis–condensation polymerization. Structure–property relationships were determined as methyl vs phenyl content was varied. These HB POSS polymers were then functionalized with curable alkoxysilane end groups and formulated with linear polysiloxanes to fabricate transparent and robust nanostructured POSS-containing coatings for use in a range of high-performance space and solar applications.