Siloxane block copolymer nanoporous foams, methods of manufacture thereof and articles comprising the same
View Patent ↗Disclosed herein is a foam that includes a polysiloxane block copolymer; the polysiloxane block copolymer including a first block that comprises a polysiloxane block and a second block that includes an organic polymer; the second block not containing a polysiloxane; the polysiloxane block being about 5 to about 45 repeat units; the foam having average pore sizes of less than or equal to about 100 nanometers.
1. A foam comprising:
a polysiloxane block copolymer; the polysiloxane block copolymer comprising a first block that comprises a polysiloxane block and a second block that comprises a polycarbonate, a copolyester-carbonate, a polyester, a polyarylate, or a combination comprising at least one of the foregoing polymers; the second block not containing a polysiloxane; the polysiloxane block being about 5 to about 45 repeat units; the foam having average pore sizes of less than or equal to about 100 nanometers; where the polysiloxane block has the structure
wherein each occurrence of R 3 is the same and is independently a C 1-6 hydrocarbyl.
2. The foam of claim 1 , wherein the block copolymer has the structure of Formula (I)
where the polysiloxane blocks are endcapped with eugenol, where x is about 1 to about 45, y is about 1 to about 99 and z is about 1 to about 99.
3. The foam of claim 1 , where the second block is a polycarbonate.
4. The foam of claim 3 , Where the polycarbonate has a molecular weight of about 500 to about 50000 grams per mole.
5. The foam of claim 1 , where the first block is present in an amount of about 1 to about 25 wt %, based on the total weight of the polysiloxane block copolymer.
6. The foam of claim 1 , where the foam has individual pores that have diameters of about 1 to about 100 nanometers.
7. The foam of claim 1 , where the foam has a transparency of about 70% to about 99% percent when measured at a thickness of 3 millimeters as per ASTM D 1003.
8. The foam of claim 1 , where the foam has a bulk density of about 0.05 to about 1 grams per cubic centimeter.
9. An article comprising the foam of claim 1 .
10. A method comprising:
immersing a polysiloxane block copolymer with fluid to form a fluid saturated polysiloxane block copolymer; the polysiloxane block copolymer comprising a first block that comprises a polysiloxane block and a second block that comprises a polycarbonate, a copolyester-carbonate, a polyester, a polyarylate, or a combination comprising at least one of the foregoing polymers; the second block not containing a polysiloxane; the polysiloxane block being about 5 to about 45 repeat units;
increasing the temperature of the fluid saturated polysiloxane block copolymer; and
foaming the polysiloxane block copolymer to form a foam that has average pore sizes of less than or equal to about 100 nanometers.
11. The method of claim 10 , where the fluid is carbon dioxide.
12. The method of claim 10 , wherein the immersing is conducted at a pressure of about 20 kilograms-force per square centimeter to about 1,000 kilograms-force per square centimeter.
13. The method of claim 10 , wherein the temperature is increased to about 50 to about 200° C.
14. The method of claim 10 , further comprising quenching the foam into a bath maintained at a temperature that is below the glass transition temperature of the second block.
15. The method of claim 10 , wherein the immersing of the polysiloxane block copolymer with fluid to form a fluid saturated polysiloxane block copolymer is conducted in an extruder or in an injection molding machine.
16. An article manufactured by the method of claim 10 .