Nanostructured dendrimer-based networks with hydrophilic polyamidoamine and hydrophobic organosilicon domains

Covalently cross-linked, three-dimensional nanodomained networks were prepared from radially layered poly(amidoamine-organosilicon) (PAMAMOS) copolymeric dendrimers containing hydrophilic polyamidoamine (PAMAM) interiors and reactive hydrophobic organosilicon (OS) exteriors. Two different types of curing chemistries were used, including (a) a sol-gel-type hydrolysis of alkoxysilyl-terminated dendrimers followed by a silanol condensation reaction and (b) irradiation or heat-induced, free-radical double-bond opening of vinylsilyl- or allylsilyl-terminated dendrimers, followed by free-radical coupling into carbosilane bridges. The first-mentioned process was investigated in more detail by monitoring the time-dependent weight loss, the glass transition temperatures (T-g), and the FT-IR spectroscopy of the resulting products. The effects of various coreagents, including acryloyldimethoxy-methylsilane (DMOMS), tetraethoxysilane (TEOS) and alpha,omega-telechelic poly(dimethylsiloxane) disilanol (PDMS), on the structures and properties of the resulting networks, especially their T-g's, were examined. It was found that, by varying the type of the PAMAMOS dendrimer network precursor, the type and relative amount of the coreagent, and the set of curing conditions used,. different films, sheets, and coatings can be obtained. These were characterized by contact angle measurements, AFM, SEM, EDS; XPS, SANS, and SAXS analyses. The results obtained revealed smoothness at the nanoscopic level and low surface energy of these network materials and confirmed uniform distribution of well-defined hydrophilic PAMAM domains within the hydrophobic OS matrixes. Most importantly, sizes and shapes of these nanoscopic domains can be controlled by the selection of dendrimer network precursors and by conditions applied to the network formation.