Porous polymeric foam

A highly porous polymeric foam can be prepared through emulsion templating by polymerizing the continuous phase of high internal phase emulsions [150], A maleimide-terminated aryl ether sulfone oligomer was copolymerized with divinylbenzene in the continuous phase, using a mixed surfactants system, cetyltrimethylammonium bromide, dodecylbenzene-sulfonic acid sodium salt, and a peroxide initiator. The polymers show a CO2 adsorption and improved mechanical properties. The materials exhibit an open cell and a secondary pore structure with surface areas of a 400 m g ... 

Kadiyala S, Lo H and Leong K W, Formation of highly porous polymeric foams with controlled release capability . In Tissue Engineering Methods and Protocols, ed. J R Morgan and M L Yarmush, Humana Press, USA, 1999, 57 65. 

Gaseous and particulate pollutants are withdrawn isoldnetically from an emission source and collected in a multicomponent sampling train. Principal components of the train include a high-efficiency glass- or quartz-fiber filter and a packed bed of porous polymeric adsorbent resin (typically XAD-2 or polyurethane foam for PCBs). The filter is used to collect organic-laden particulate materials and the porous polymeric resin to adsorb semivolatile organic species (com-... 

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]. 

Polymeric foams, called polyHIPE , has been developed by Unilever researchers5. The production of these porous materials was based on the polymerisation of high internal phase emulsion (HIPE)6. The system is composed of two phases an organic phase -called the continuous phase- containing the monomers and a suitable amount of emulsifier and an aqueous phase -called the dispersed phase- containing the radical initiator (scheme 1). 

Polymeric foam dressings are a diverse group of products with a wide range of properties. At their simplest, they are foamed polymers that have been made into sheets. The wound contact layer is often heat treated and pressure modified to produce a hydrophilic porous membrane about 0.5 mm thick to give a smooth, nonadherent wound contact surface that absorbs fluids by... 

Poroplastic and Sustrelle ultramicroporous cellulose triacetate Porous polymeric substrates and foams Monolithic systems... 

A major issue associated with the use of SCCO2 as a solvent for polymerization is the reaction pressure many of the processes published so far operate at pressures in the range 20.0-40.0 MPa [1, 15], which has significant implications for capital equipment and running costs. This problem has been approached in a number of ways. For example, DeSimone and coworkers have developed methods for the continuous precipitation polymerization of fiuoropolymers [16]. In general, continuous SCF processes are likely to be more readily implemented than batch processes, and a continuous approach has also been applied to the processing of porous PVDF foams [17]. 

Figure 9.1 Porous structure of a human bone (left) and porous structure of a nanoporous polymeric foam (right).

Nanocarbons can also be deposited onto surfaces via electrochemistry, such as electrophoretic deposition described earlier. A method for one-step electrochemical layer-by-layer deposition of GO and PANI has been reported by Chen et al. [199]. A solution of GO and aniline was prepared and deposited onto a working electrode via cyclic voltammetry. GO was reduced on the surface when a potential of approx. -1 V (vs. SCE) was applied compared to the polymerization of aniline which occurred at approx. 0.7 V (vs. SCE). Repeated continuous scans between -1.4 to 9 V (vs. SCE) resulted in layer by layer deposition [199]. A slightly modified method has been reported by Li et al. who demonstrated a general method for electrochemical RGO hybridization by first reducing GO onto glassy carbon, copper, Ni foam, or graphene paper to form a porous RGO coating [223]. The porous RGO coated electrode could then be transferred to another electrolyte solution for electrochemical deposition, PANI hybridization was shown as an example [223]. 

A separator is a porous membrane placed between electrodes of opposite polarity, permeable to ionic flow but preventing electric contact of the electrodes. A variety of separators have been used in batteries over the years. Starting with cedar shingles and sausage casing, separators have been manufactured from cellulosic papers and cellophane to nonwoven fabrics, foams, ion exchange membranes, and microporous flat sheet membranes made from polymeric materials. As batteries have become more sophisticated, separator function has also become more demanding and complex. 

To make a solid foam we start from a liquid foam and induce solidification. This can be achieved by a chemical polymerization (Styrofoam), by lowering the temperature (pumice stone or a souffle), or by increasing the temperature to induce a structural transition (baking of bread). Porous solids can appear as solid foams because of their low density and their high content of gas. The difference between the two is that in a porous solid we have a bicontinuous structure while the individual cavities in a foam are closed. This is an important difference because porous solids tend to adsorb liquids due to capillary effects and then completely change their properties. 

Water-in-Monomer Polymerizations for Open-Celled Foams. Porous polymers or mixed polymers of styrene are prepared by polymerizing the... 

C/W emulsions may be used as templates in the formation of porous polymers, as shown in Figure 5 (52). Polymerization takes plaee in the aqueous phase eontinuous channels between the CO2 droplets. The CO2 is vented and the water is removed to form a porous polymer. The median pore diameter on the order of 1 pm reflects the size of the original CO2 droplets. Polymer foams may be used as adsorbents, as substrates for catalysts, and as scaffolds in biomedical engineering. 

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