Phase separation foam control

It is our intention to present strategies based on chemically induced phase separation (CIPS), which allow one to prepare porous thermosets with controlled size and distribution in the low pm-range. According to lUPAC nomenclature, porous materials with pore sizes greater than 50 nm should be termed macroporous [1]. Based on this terminology, porous materials with pore diameters lower than 2 nm are called microporous. The nomination mesoporous is reserved for materials with intermediate pore sizes. In this introductory section, we will classify and explain the different approaches to prepare porous polymers and to check their feasibility to achieve macroporous thermosets. A summary of the technologically most important techniques to prepare polymeric foams can be found in [2,3]. 

Various fabrication methods have been developed in order to attain the 3D scaffold characteristics. In the case of synthetic polymer or polymer-matrix composite scaffolds, the methods include [47] solvent casting and particle leaching, phase separation, extrusion, gas foaming, and free form fabrication. Each method presents certain advantages with respect to others, ranging from ease of manufacture to control of the microstructure/nanostructure. Solvent casting and phase separation methods have been studied at our laboratory. 

Thermally-induced phase separation has been applied to the production of polysilane foams. Variation of polymer concentration, solvent type, and cooling rate have been used to refine the macrostructure. Both these membrane production methods rely on the formation of aggregates of controlled size and shape as discussed in the previous section. 

Using effervescent materials, the pore size of the pol5mier scaffolds can be easily controlled, and biodegradable polymer scaffolds can be more simply prepared compared to conventional methods such as salt leaching technique, phase separation technique, or gas foaming technique. 

An essential piece of equipment in recyclable systems is a well-designed mud-gas separator. The function of the separator is to disengage the gas and liquid phases. When the foam control additive is introduced... 

Lo H, PonticieUo MS, Leong KW. Fabrication of controlled release biodegradable foams by phase separation. Tissue Eng 1995 1 15-28. 

Structure relies primarily on the fabrication process. Conventional methods for these pore-strucmred scaffolds include fibre bonding, solvent carting/particulate leaching, gas foaming and phase separation. The porous scaffolds processed using these techniques have controlled pore size and porosity suitable for tissue engineering. 

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