Polymeric foams with nanocellular morphology and methods for making them

A method of making a foamed polymeric article, comprising:

• melting a polymeric material having structural units derived from 2-hydrocarbyl-3,3-bis(hydroxyphenyl)phthalimidine compounds;
• diffusing a blowing agent into the polymeric material to form a mixture;
• nucleating bubbles in the mixture at a sufficient temperature and pressure to enable the production of foam cells having an average diameter of about 1 nanometer to about 1000 nanometers;
• stabilizing the foam cells;
• and forming the mixture into a desired shape.

A method for forming a foamed article, comprising:

• melt extruding a polycarbonate polymer comprising structural units derived from 2-phenyl-3,3-bis(hydroxyphenyl)phthalimidine compounds;
• saturating the polycarbonate polymer with blowing agent at a pressure and at a temperature effective to saturate the polycarbonate polymer with greater than 10 percent by weight of the polymer;
• nucleating bubbles in the mixture at a sufficient temperature and pressure to enable the production of foam cells having an average diameter of about 1 nanometer to about 1000 nanometers;
• and
• stabilizing the foam cells to form the foamed article.