New Method to Fabricate Macroporous Polymers with Tunable and Oriented Voids for Filtration and Optical Applications
- Detailed Technology Description
- Methods for Precision Fabrication of Macroporous Polymers and Colloidal Crystals
- *Abstract
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The fabrication of polymeric materials with ordered submicron-sized void structures is potentially valuable for many separation technologies as well as for emerging optical applications. Macroporous materials, those with pore diameters greater than 50 nm, have a wide range of applications in chemistry. Macroporous polymers, in particular, can be used as catalytic surfaces and supports, separation and adsorbent media, biomaterials, chromatographic materials, and thermal, acoustic, and electrical insulators. In nearly every case, the utility of the porous system is a sensitive function of the internal pore diameters, their distribution, and their morphology. As a result, most of the synthetic approaches to creating these materials, both polymeric and inorganic, have focused on creating internal voids with monodisperse and controllable diameters. Toward this end, Rice researchers across the Departments of Chemistry, and Electrical and Computer Engineering and the Rice Quantum Institute have developed macroporous polymer membranes with tunable and oriented voids, in this case for filter applications.
This invention provides a general strategy for fabricating macroporous polymers with tunable and oriented voids for filtration applications. These membranes are made using a colloidal crystal template of silica microspheres. The method of fabrication is such that it is possible to control the sizes of the interconnecting pores between the larger cavities defined by the starting silica colloidal templates. The air between the spheres can be replaced by monomers that can be subsequently polymerized or directly by commercial available polymers. The use of silica microspheres as templates makes it possible to employ chemical rather than thermal methods for template removal. For this reason, polymers as diverse as polyurethane and polystyrene can be created as freestanding macroporous films, with thicknesses ranging from 0.5 to 50 microns. Scanning electron microscopy of these samples indicates a well-formed porous structure consisting of voids ranging from 200 to 400 nm in diameter.
Control over the inner pores connecting the larger voids provides a method of size-dependent separation. Those large voids are not isolated, but rather interconnected by a network of monodisperse smaller pores, of 50 to 130 nm, whose size can be controlled by varying the polymerization temperature.
In addition, macroporous polymers with stacked multilayers of voids of different sizes can be made for the first time from the stacked silica colloidal crystals. Polymers incorporating these stacked multilayers of voids improve the filtration efficiency by pre-filtering the larger particles. These membranes exhibit striking optical properties due to the periodic arrangement of air spheres in the polymer medium and can be made in both planar and curved shapes, which can be used as optical filters and other optical applications.
The discovery that the commercially-available polymers can be directly used to make macroporous polymers reveals the possibility in fabricating these filtration membrane in large scale in an economical way. These polymeric membranes may also find application in other modern separation technologies, such as the stationary phases of the liquid chromatography. Researchers at Rice have also shown that these membranes can be used as templates to form artificial opals from nearly every major class of functional materials, which may lead to important applications as drug delivery media, high density magnetic recording materials, optical filters and pigments, as well as photonic band gap materials with improved properties. Rice is pursuing patent rights to this technology under a pending patent application.
Patent Status: Patent Pending
For more information, contact:
Mark Staudt
713-348-5580
mstaudt@rice.edu
- Country/Region
- USA
