Organic-inorganic polyamidoamine (PAMAM) dendrimer-polyhedral oligosilsesquioxane (POSS) nanohybrids

A series of novel core-shell organic-inorganic hybrid materials having polyamidoamine (PAMAM) dendrimer cores and polyhedral oligosilsesquioxane (POSS) shells were prepared. Compositional variety of these hybrids was achieved by varying the dendrimer generation and POSS content. Structures were confirmed by H-1, C-13, and Si-29 NMR, IR, and MALDI-TOF mass spectrometry where trihydroxyacetophenone monohydrate (TAM) was used as a matrix. Structure-property relationships across a range of dendrimer generations and POSS contents were studied. Glass transition temperatures varied with the degree of dendrimer end group substitution and generation, while melting temperatures were largely unaffected by degree of end group substitution. Solubility characteristics were directly related to POSS content and were practically independent of dendrimer generation. Best quality transparent films were obtained when a quarter of the dendrimer amino end groups were reacted with POSS, which corresponded to an approximately one-to-one dendrimer to POSS mass ratio. Cross-linkable variants of film-forming hybrids were synthesized by reacting a portion of the PAMAM amino end groups with 3-acrylopropyldimethoxymethylsilane (DMOMS). These hybrids yielded transparent, robust films by moisture cure in ambient air.