Alkoxy-modified silsesquioxane compounds are described. The alkoxy-modified silsesquioxane compounds contain an alkoxysilane group that participates in an alkoxysilane-silica reaction as a silica dispersing agent in rubber, with the release of zero to about 0.1% by weight of the rubber of volatile organic compounds (VOC), especially alcohol, during compounding and further processing. Further described are methods for making alkoxy-modified silsesquioxanes, methods for making vulcanizable rubber compounds containing alkoxy-modified silsesquioxanes, vulcanizable rubber compounds containing alkoxy-modified silsesquioxanes, and pneumatic tires comprising a component that contains alkoxy-modified silsesquioxanes.