Polyhedral oligomeric silsesquioxane grafted polymer in polymeric foam

1. A polymeric foam article comprising a polymer matrix that defines multiple cells therein, wherein the polymer matrix comprises a polymer component consisting of all the polymers in the polymer matrix and comprising a first polymer that is a polyhedral oligomeric silsesquioxane grafted polymer that has a weight-average molecular weight of two kilograms per mole or higher and 80 kilograms per mole or lower and wherein the polymeric foam article has a thickness of more than 1.5 millimeters and wherein the polymer component comprises a second polymer blended with the first polymer, the second polymer being free of polyhedral oligomeric silsesquioxane and being miscible with the first polymer.

2. The polymeric foam article of claim 1 , wherein the second polymer is a (meth)acrylic polymer.

3. The polymeric foam article of claim 1 , further characterized by having an average cell size that is less than 0.5 micrometers.

4. The polymeric foam article of claim 1 , further characterized by having an a porosity of 70 percent or more and at least one of the following characteristics: (i) an average cell size of 250 nanometers or less; and (ii) a nucleation density of 5×10 14 cm −3 or higher.

5. The polymeric foam of claim 1 , further characterized by having a porosity of 80 percent or more.

6. The polymeric foam article of claim 1 , further characterized by more than 50 weight-percent of the polymers in the polymer component are second polymers selected from styrenic copolymers and (meth)acrylic polymers.

7. The polymeric foam article of claim 1 , wherein the concentration of polyhedral oligomeric silsesquioxane that is grafted to polymer is 0.05 weight-percent or more and seven weight-percent or less based on total weight of polymer component.

8. A process for preparing the polymeric foam article of claim 1 , the process comprising blending a polymer component with a blowing agent at an initial pressure to form a foamable polymer composition and then expanding the foamable polymer composition into a polymeric foam article of claim 1 at a pressure below the initial pressure, the polymer component comprising a first polymer that is a polyhedral oligomeric silsesquioxane grafted polymer that has a weight-average molecular weight of two kilograms per mole or higher and 80 kilograms per mole or lower and wherein the polymer component comprises a second polymer blended with the first polymer, the second polymer being free of polyhedral oligomeric silsesquioxane and being miscible with the first polymer.

9. The process of claim 8 , wherein the second polymer is a (meth)acrylic polymer.

10. The process of claim 8 , wherein the blowing agent comprises carbon dioxide.

11. The process of claim 8 , characterized by forming a foamable polymer composition comprising first polymer that is a polyhedral oligomeric silsesquioxane grafted polymer and blowing agent that comprises carbon dioxide and allowing the foamable polymer composition to expand into a polymeric foam characterized by having a porosity of 70 percent or more and at least one of the following characteristics: (i) an average cell size of 250 nanometers or less; and (ii) a nucleation density of 5×10 14 cm −3 or higher.

12. The process of claim 8 , further comprising the step of preparing the polymer component in an absence of solvent that is subsequently removed prior to or during expansion of the polymer component into the polymeric foam article.