Material systems and methods of manufacture for auxetic foams

An auxetic foam formed from a material system, the material system comprising:

• a bulk matrix comprising:
• a soft domain comprising a polymer chain and having a first glass transition temperature;
• and
• a hard domain covalently or non-covalently linked to the polymer chain of the soft domain and having a thermal transition temperature greater than the first glass transition temperature;
• and
• a filler polymer dispersed in the bulk matrix and having a second glass transition temperature greater than the first glass transition temperature and less than the thermal transition temperature;
• the material system being a multiphase, multicomponent polymer foam having an initial volume and having a plurality of cells;
• wherein the auxetic foam is produced by a method comprising:
• placing the multiphase, multicomponent polymer foam into a pressure chamber and compressing the foam to a compressed volume less than the initial volume, such that the cells are deformed;
• exposing the compressed foam within the pressure chamber to a compressed gas, the compressed gas comprising carbon dioxide or nitrogen, and maintaining the pressure chamber at a predetermined temperature and a predetermined pressure for a predetermined time;
• dissolving at least a portion of the compressed gas into the filler polymer and reducing the second glass transition temperature of the filler polymer such that the filler polymer transitions from a glassy state to a rubbery state, wherein a shape of the filler polymer changes from generally spherical to generally ellipsoidal when the compressed gas dissolves into the filler polymer;
• and
• allowing the foam to reach atmospheric pressure and removing the foam from the pressure chamber such that the filler polymer transitions from the rubbery state to the glassy state and the filler polymer retains the generally ellipsoidal shape, thereby fixing the cells of the foam in the deformed state, thereby forming the auxetic foam.