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In analogy to piezoelectric materials, where the application of an electrical field creates mechanical deformation in the material, I have the following question.

Are there solid materials whose porosity can be altered or controlled?

Of course, I have googled this. This lead me to a lot of websites where controllable porosity means that the porosity of a material is very-well defined when it is produced. This is not what I am looking for. I am looking for a material that can alter its porosity according to an external control quantity, such as electric voltage.

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    $\begingroup$ Perhaps you can try googling "tunable" instead of "conytolled/-able" $\endgroup$ – Slaviks Aug 6 '13 at 14:44
  • $\begingroup$ I know porosity can be changed due to temperature or pressure, but as for controlling it with electricity or something that is as easily used, I am unsure. I feel that it's certainly possible though. $\endgroup$ – danielunderwood Aug 6 '13 at 14:46
  • $\begingroup$ I can imagine systems to solve the problem (porous plug under controlled pressure; dialing the temperature of a filter with nice linear expansion) and so on, but I don't know of anything as simple as the piezo response. Are there other constraints to make those kinds of idea infeasible? $\endgroup$ – dmckee Aug 6 '13 at 14:47
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The credit should actually go to Slaviks for the wise suggestion of keywords to look for. Tunable porosity gives the following article:

  • DOI:10.1002/ange.201201686 Prashant Tyagi et al. Dynamic Interactive Membranes with Pressure-Driven Tunable Porosity and Self-Healing Ability. Angewandte Chemie, 2012.

Copolymer

ABA triblock copolymer (pictured above) poly(styrene-co-acrylonitrile)-b-poly(ethylene oxide)-b-poly(styrene-co-acrylonitrile) (PSAN-b-PEO-b-PSAN) has been used to generate flower-like micelles.

Porosity tuning is done by changing water pressure which re-arranges the micelles.

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  • $\begingroup$ I agree, [Slavik]'s suggestion makes all the difference. $\endgroup$ – seb Aug 7 '13 at 6:55
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I would expect stimuli-responsive polymers to have what you're looking for, and the keyword "stimuli-responsive" may be a useful search term. The stimuli-responsive polymers undergo conformational changes in response to changes in their environment. The primary environmental control variables people use are temperature, pH, and ionic strength. But people have also looked at glucose, visible light, and electric and magnetic fields. Usually this happens in solution, but you can also make hydrogels out of these polymers. In that case, the hydrogels swell or deswell when you hit them with the stimulus.

I just found this paper, so I haven't read it, but it appears to describe exactly what you are looking for, by using stimuli-responsive polymers. The full citation is J. Mater. Chem., 2012,22, 19482-19487. I've heard of Sergiy Minko in the context of stimuli-responsive polymers, so he's probably a good person to look for.

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