received by the International Bureau on 14 August 2018 (14.08.2018)

WHAT IS CLAIMED IS

1. A polymeric material that comprises a thermoplastic composition, the composition containing a continuous phase that contains a polyester, wherein a copolyetherester elastomer is dispersed within the continuous phase in the form of discrete domains, and wherein a porous network is defined within the thermoplastic composition that includes a plurality of nanopores.

2. The polymeric material of claim 1 , wherein the copolyetherester elastomer constitutes from about 0.01 wt.% to about 15 wt.% of the thermoplastic composition.

3. The polymeric material of claim 1 , wherein the polyester is polylactic acid.

4. The polymeric material of claim 1 , wherein the polyester is an aromatic polyester.

5. The polymeric material of claim 4, wherein the aromatic polyester is polyethylene terephthalate.

6. The polymeric material of claim 1 , wherein the polyester has a glass transition temperature of about 0°C or more.

7. The polymeric material of claim 1 , wherein the elastomer is a segmented block copolymer that has recurring long chain ester units and short chain ester units.

8. The polymeric material of claim 7, wherein the long chain units are represented by the formula:

-OGO-C(0)-R-C(0)- and the short chain ester units are represented by the structure:

-ODO-C(0)-R-C(0)- wherein,

G is a divalent group that is derived from one or more high molecular weight alcohols;

R is a hydrocarbon group derived from one or more dicarboxylic acids; and

D is a divalent group derived from one or more low molecular weight diols.

9. The polymeric material of claim 7, wherein the long chain units are formed from the reaction product of a high molecular weight alcohol with a dicarboxylic acid.

10. The polymeric material of claim 9, wherein the alcohol is a polymeric glycol.

11. The polymeric material of claim 7, wherein the short chain ester units are formed from the reaction of a low molecular weight diol with a dicarboxylic acid.

12. The polymeric material of claim 11, wherein the low molecular weight diol includes ethylene glycol, propylene glycol, 1 ,4-butanediol, 1,6-hexamethylene glycol, dihydroxycyclohexane, cyclohexane dimethanol, resorcinol, hydroquinone, 1 ,5-dihydroxynaphthalene, bisphenol A, or an ester derivative thereof.

13. The polymeric material of any of claims 8 to 12, wherein the dicarboxylic acid includes an aromatic dicarboxylic acid.

14. The polymeric material of claim 1 , wherein the nanopores have an average cross- sectional dimension of about 800 nanometers or less.

15. The polymeric material of claim 1 , wherein nanopores have an average axial dimension of from about 100 to about 5000 nanometers.

16. The polymeric material of claim 1 , wherein the continuous phase constitutes from about 60 wt.% to about 99 wt.% of the thermoplastic composition.

17. The polymeric material of claim 1 , wherein the copolyetherester elastomer is dispersed in the form of nano-scale domains.

18. The polymeric material of claim 1 , wherein the composition further comprises a microinclusion additive dispersed within the continuous phase in the form of discrete domains.

19. The polymeric material of claim 1 , wherein the porous network further includes micropores.

20. A fiber comprising the polymeric material of claim 1.

21. A nonwoven web comprising the fiber of claim 20.

22. An absorbent article that includes a substantially liquid-impermeable layer, liquid- permeable layer, and an absorbent core, wherein the substantially liquid-impermeable layer, the liquid- permeable layer, or both include the polymeric material of claim 1.

23. A method for forming a polymeric material, the method comprising:

forming a thermoplastic composition that contains a continuous phase that includes a polyester and a copolyetherester elastomer that is dispersed within the continuous phase in the form of discrete domains; and

solid state drawing the thermoplastic composition to form a porous network therein, the porous network including a plurality of nanopores.

24. The method of claim 23, wherein the thermoplastic composition is drawn to a stretch ratio of from about 1.1 to about 25.

25. The method of claim 23, wherein the thermoplastic composition is drawn at a temperature of from about -50°C to about 150°C.

26. A method for forming a fiber, the method comprising:

forming a thermoplastic composition that contains a continuous phase that includes a polyester and a copolyetherester elastomer that is dispersed within the continuous phase in the form of discrete domains;

extruding the composition through a capillary to form the fiber; and

drawing the fiber at a temperature that is lower than the melting temperature of the polyester, thereby forming a porous network that includes a plurality of nanopores.

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