Block Copolymer-Assisted Microcellular Supercritical CO2 Foaming of Polymers and Blends

The behaviour in supercritical CO2 of block copolymers containing styrenic, butadiene, and methacrylic or perfluroalkyl blocks is studied in view of a specific swelling and foaming by a gas dissolution process. These block copolymers are considered as neat materials or as additives in blends e.g in polystyrene (PS) or polymethylmethacrylate (PMMA) matrices. In both cases (neat or blend) the copolymers may exhibit a structuration at a micro or nano level. The phase separated (nano) structures depend on the block type and the concentration of copolymers in the polymer matrix, so that micelles, vesicles, lamellas, or warm-like structures are generated. Furthermore when one block is chosen as a highly CO2-philic moiety, the nanostructures are able to act as CO2 reservoirs. The result is the possibility to control microcellular foaming, or sometimes nanocellular foaming, of commodity amorphous polymers such as PMMA and PS. Besides, at room temperature, the blocks can be either glassy or rubbery in order to freeze the growth and coalescence of cells during foaming. [PUBLICATION ABSTRACT]