Preparation, Characterization, and Properties of Novel PSMA−POSS Systems by Reactive Blending

Novel hybrid systems based on styrene−maleic anhydride copolymers (PSMA) and a polyhedral oligomeric silsesquioxane characterized by an amino group as reactive side (POSS-NH2) have been synthesized by one-step reactive blending. The features of the above materials were compared with those of systems based on polystyrene (PS) or an unreactive POSS in order to highlight the effect of both the reactivity of the silsesquioxane and the polymer matrix functionality on the material final characteristics. FTIR measurements evidenced the occurrence of imidization reaction between the MA group of PSMA and the amino group of POSS molecule, with the consequent formation of a cyclic imide linkage binding POSS to the polymer backbone. This reaction turned out to promote POSS distribution in the polymer matrix, as only the systems characterized by the aforementioned functionalities allowed to obtain a silsesquioxane dispersion at nanometric level. By following the evolution of the system features, in terms of glass transition temperature (Tg), morphology, yield, and crystallinity, with the mixing time, it has been verified that using a Tmix lower than POSS melting temperature, a surface reaction at the POSS crystal/polymer boundary occurs, leading to the formation of a very peculiar two-phase structure evolving with time. The two phases have been found to contain different POSS concentrations. Biphasic systems, studied by means of differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA), have showed two Tg, depending on the presence of unbound POSS acting as a plasticizer. Films prepared from the systems PSMA−POSS containing low amounts of silsesquioxane (up to 10 wt %) have been found to be completely transparent, while the transparency of those based on higher POSS content has been achieved only after removing the unbound POSS. Indeed, the role of silsesquioxane on surface properties has been assessed by evaluating film wettability.