Low-Density Nanocellular Foams Produced by High-Pressure Carbon Dioxide

A new type of nanocellular polymeric material based on PMMA and a MAM triblock copolymer is presented. The production avoids the use of physical additives and leads to completely homogeneous nanostructured polymers with a large number of CO2 nucleation sites. The foamed materials show average cell sizes <200nm and relative foam densities of 0.4, presenting a homogeneous cell structure. A physical effect not measured before in nanocellular materials is demonstrated, which leads to an increase of the glass transition temperature due to the confining effect of PMMA chains in the cell walls of the nanocellular foam. The effects of changing saturation pressure and MAM content in the cellular structure are described, together with three-point bending Young's modulus measured using DMA.