Please try the method of UCST. 

You may use freeze-drying method. Porosity depends on what rate you freeze the solution. Attached image is freeze-dried 2% chitosan in 0.2M acetic acid/water with a chilling rate of -10 Celsius degree/min.

Hi Kevin,

electro spinning might work depending on the desired sponge dimensions.

Thanks everyone, I do not favor electrospinning due to the high density of fabric. Freeze-drying is of interest. Do you have any example papers using UCST with these polymers? 

Hello Kevin,

We have good experience with the freeze extraction & particulate leaching method for PLA and PCL scaffolds, for porosity around 90%. Attached is a paper from friends also working in the field.

Article Influence of the macro and micro-porous structure on the mec...

Try using freeze gelation. It just needs a normal freezer, much more time and energy efficient than freeze drying or salt leaching. Look up Ho et al work in 2004 in Biomaterials  journal.

pores can be controlled it is sort of a thermally induced phase separation process. and you can use bioceramics as well.

If you want to keep it simple, you can use solvent casting-particle leaching. You only need particles of salt of the desired size and molds.

Hi, you can use this information. Thanks.

Thesis Aplicación de la liofilización para la obtención de andamios de PLLA.

To measure the porosity, you could try mercury porosimetry. Another method to fabricate porous scaffolds is freeze casting. You could check if the link attached gives you any ideas!