Incorporation and chemical effect of Sn-POSS cages in poly(ethyl methacrylate)

Organic-inorganic hybrids based on poly(ethyl methacrylate) and Sn-POSS nano-building blocks were prepared via radical polymerization of ethyl methacrylate, in which Sn-POSS was dissolved. Sn-POSS was incorporated as non-functional or as bis(acrylamido)-functional unit, at the concentrations of 0.5-10 wt%. Both Sn-POSS cage types were shown to prevent the oxidative degradation of the matrix modulus, without causing an excessive crosslinking even at the highest Sn-POSS concentration. A very marked effect is, that the Sn-cages cause the preservation of the impact toughness of the poly(ethyl methacrylate)/Sn-POSS hybrids, if the latter are subjected to oxidation, while the impact toughness of the neat matrix decreases by one order after the same treatment. The effect of the Sn-POSS cages can be explained by radical reactions, in which the cages reconnect matrix chains previously interrupted by oxidative scission. The Sn-POSS thus practically causes a "reconstruction" of the interrupted linear chains. The process is already very efficient between 0.5 and 1 wt% of Sn-POSS.