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 A(8)-B-2 polymerization (BMNLP) and characterized by IR, H-1 NMR, Si-29 NMR, SEC, DSC, and for refractive index. Series 1 was prepared from T(8)vinyl(8) and disilane monomers, and series 2 was prepared from T-8(OSiMe2H)(8) and divinylsilane monomers (where T denotes an SiO3 unit), both via platinum-catalyzed hydrosilylation polymerization. Series 3 was prepared from T-8(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.