Interconnected pore structures

Fig. 8. Schematic interconnected pore structure represented by a superposition of an identical pore with density p (r — r,). The average pore spacing is b and the pore size is a.

Thermally induced phase separation [33, 37] High porosities ( 95%) Highly interconnected pore structures Anisotropic and tubular pores possible Control of structure and pore size by varying preparation conditions Long time to sublime solvent (48 h) Shrinkage issues Small scale production Use of organic solvents... 

Macroporous gels Another technique to obtain fast-responsive hydrogels is to create voids (pores) inside the hydrogel matrix, so that the response rate becomes a function of the microstructure rather than the size or the shape of the gel samples (Okay 2000). For a polymer network having an interconnected pore structure, absorption or desorption of water occurs through the pores by convection, which is much faster than the diffusion process that dominates the non-porous hydrogels. 

The values of dj =0.963 and dj = 0.037 are for a little sphere embedded in a stiff porous matrix with interconnected pore structure, as given in Pride and Berryman (2003). 

The motivation for preparing conductive aerogels stems from the desire to be able to transport electrons through the nanostmcture (solid network). When coupled to the high surface area and interconnected pore structure, this architecture enables ions or molecules to be transmitted to the surface where they can be reduced or oxidized by the conductive network. For this reason, such materials are being explored for charge storage and electrocatalytic applications. 

For the purposes of this review, we restrict the definition of PIMs to organic polymers which have interconnected pore structures and which exhibit appreciable apparent inner surface areas by gas sorption analysis. PIMs can be linear polymers (Sect. 2.2.1) or networks (Sect. 2.2.2). While other network polymers may be microporous (e.g. Sect. 2.1 and 2.4), it is this porosity of the linear analogues that distinguishes PIMs. Again, the area of PIMs has been reviewed quite recently [41,42] so relatively brief details are given here. 

After lubricant removal, the PTFE film is submitted to an uniaxial or biaxial stretching, giving rise to an interconnected pore structure. The process was proposed by Gore [109] and the resulting porous film is today a successful product in the membrane and textile industry. For uniaxial stretching, the nonsintered film from the paste extrusion is fed to a machine with heating rollers, where... 

Matrix systems for controlled release applications are predominately for delivery of soluble substances. Siegel and Langer (1984) revealed that large molecules, such as insulin, heparin, and albumin, were released over an extended period of time owing to the slow diffusion through the interconnected pore structure. 

Thermally induced liquid-liquid phase separation can he utilized to fabricate scaffolds for tissue engineering. For example, a solvent can be selected, where the crystallization temperature is sufficiently lower than the liquid-liquid phase separation temperature of an amorphous polymer solution. A liquid-liquid phase separation can be induced by lowering the temperature into the imstable region on the phase diagram but above the solvent crystallization temperature. For the PLA and PLGA family, a mixture of dioxane and water has been used for liquid-liquid phase separation to fabricate pol5mier scaffolds with interconnected pore structure (Fig. 12) (112,113). 

Electrospinning is a simple and efficient method to prepare polymer membranes with fully interconnected pore structure and micron-sized fibers. The electrospinning technique has been generally considered as a variant of the electrostatic spraying or... 

The synthesis of OMC involves the use of ordered mesoporous silica (OMS) template with a specific pore topology [7]. As illustrated in Figure 3.1, the appropriate carbon precursor (carbon sources such as sucrose, furfuryl alcohol, acetylene gas, pyrrole, and acrylonitrile) is fed into the pores of the template via the infiltration approach, followed by its carbonization to achieve the siUca-carbon composite and template removal in ethanol-water solution of HF or NaOH to obtain the mesoporous carbon replica. The structure of the as-obtained OMC strongly depends on the structure of the used template. Chang et al. [7] have reviewed the synthesis of OMC as support materials for fuel cell applications. The rod- and tube-type mesoporous carbon structures can be realized by filling carbon precursors in the template pores and coating carbon precursors as a thin film on the pore walls of the template, respectively. In order to get the well-defined structure of OMC, the template should have three-dimensional interconnected pore structure. On the other hand, the carbonization of the carbon precursors should be confined exclusively within the mesopores of the ordered mesoporous silica templates with sufficient carbon precursor filling therefore, before the pyrolysis process, the carbon soiu-ce should be converted to a cross-linked polymer induced by the use of the acid polymerization catalysts [5,7]. 

Figure 1.4 SEM images of (a), (b) nanocomposite 30% nHA, scaffold 30% iiHA (c) before cell culture with interconnectivity (pore size 200-300 pm, 70% porosity) The arrows indicate interconnected pore structures (d) before cell culture and (e) after ceU culture. Reproduced from Torabinejad, B., et al., 2014. Synthesis and characterization of nanocomposite scaffolds based on triblock copolymer of L-lactide, e-caprolactone and nano-hydroxyapatite for bone tissue engineering. Materials Science Engineering. C, Materials for Biological Applications 42,199-210. Available at http //www.ncbi.nlm.nih.gov/pubmed/25063111 (accessed 25.09.14.).

Figure 24.S A schematic diagram of sulfur (yellow) confined in the interconnected pore structure of mesoporous carbon, CMK-3. Reproduced from Ji et al. (1).

As two important copolymers of PVDF, the P(VDF-HFP) [4] and P(VDF-CTFE) [23] had been developed for gel polymer electrolyte in LIBs. The introduction of copolymer components was to reduce the crystallinity of the PVDF chain. The reduction of crystallinity could increase the ionic conductivity. Electrospun P(VDF-HFP) and P(VDF-CTFE) fibrous membranes had been proved to show high ionic conductivities in the range of several mS cm which was attributed to the easy transportation of the liquid electrolyte through the fully interconnected pore structure of the membrane. For example, the electrospun P(VDF-HFP) fibrous membrane had high ionic conductivities in the range of 4.59 mS cm", high electrolyte uptake of 425 % at room temperature, and good electrochemical stability with a potential of over 4.5 V versus Li/Li+ [29]. 

Abstract Liquids are essential for most of the lives and activities on earth, where liquid filtration is an important tool to remove undesired suspended solids, emulsified particles, dissolved molecules, and ions from liquids by separating the permeate from the unwanted impurities through filters. Electrospun nanofibrous membranes (ENMs) have been developed as filtration media having unique advantages over traditional membranes, due to high porosity, interconnected pore structures, large surface-to-volume ratio with capability for chemical/physical functionalization, and cost-effectiveness. The new fibrous membrane format has been used in many applications, including filtration, (membrane) distillation, and pervaporation. 

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