The fabrication of ordered inorganic arrays of varying length scales and with multimodal porosities is of practical importance owing to their potential application in many areas of materials chemistry, including catalysis and separations science. [1,2] A common approach to the controlled synthesis of this class of materials, first exploited in the synthesis of the MCM-41 family of molecular sieves, is to polymerize the inorganic phase around an organic template by using a sol-gel process.[3] The organic phase is then removed by calcination leaving a void space that is a replica of the size, orientation, and arrangement in space of the template. By using multiple templates of different length scales, hierarchically porous inorganic structures containing various combinations of micro-, meso-, and macropores have been realized. [4][5][6][7][8][9] We report herein the creation of a mesoporous silica monolith that contains oriented macroporous channels, which is achieved by the application of an electric field to a hydrogel template during polymerization and cross-linking. [8,9] To the best of our knowledge, this is first time an external electric field has been used to create ordered, hierarchical meso-/ macroporous silicate materials.The template matrix is created through the electrical alignment of a polyacrylamide hydrogel, which is accomplished by copolymerizing a mixture of acrylamide functionalized with immobiline and bisacrylamide in the presence of an electric field (60 V cm À1 ). The presence of this field creates interstitial voids of approximately 10 mm in diameter. The channel structure, which can be imaged through confocal microscopy, is present in the field-oriented hydrogel (Figure 1 a), but is replaced by a disordered structure (Figure 1 b) when no field is applied.The silicate phase is introduced through the immersion of a freestanding hydrogel monolith in neat tetramethylorthosilicate (TMOS). Hydrolysis and condensation occurs as the TMOS infuses the hydrogel and reacts with water trapped in the voids. After a period of 24 h a hard solid white monolith, close in size to the hydrogel template, is formed. Calcination under O 2 at 500 8C removes the organic phase leaving a porous silica monolith.Scanning electron micrographs of this material, imaged parallel to the electric field direction (Figure 2 a), show striations oriented in the field direction. No such features are observed when the disordered template is used, which suggests that the channel/hydrogel interface is replicated

The fabrication of ordered inorganic arrays of varying length scales and with multimodal porosities is of practical importance owing to their potential application in many areas of materials chemistry, including catalysis and separations science. [1,2] A common approach to the controlled synthesis of this class of materials, first exploited in the synthesis of the MCM-41 family of molecular sieves, is to polymerize the inorganic phase around an organic template by using a sol-gel process.[3] The organic phase is then removed by calcination leaving a void space that is a replica of the size, orientation, and arrangement in space of the template. By using multiple templates of different length scales, hierarchically porous inorganic structures containing various combinations of micro-, meso-, and macropores have been realized. [4][5][6][7][8][9] We report herein the creation of a mesoporous silica monolith that contains oriented macroporous channels, which is achieved by the application of an electric field to a hydrogel template during polymerization and cross-linking. [8,9] To the best of our knowledge, this is first time an external electric field has been used to create ordered, hierarchical meso-/ macroporous silicate materials.The template matrix is created through the electrical alignment of a polyacrylamide hydrogel, which is accomplished by copolymerizing a mixture of acrylamide functionalized with immobiline and bisacrylamide in the presence of an electric field (60 V cm À1 ). The presence of this field creates interstitial voids of approximately 10 mm in diameter. The channel structure, which can be imaged through confocal microscopy, is present in the field-oriented hydrogel (Figure 1 a), but is replaced by a disordered structure (Figure 1 b) when no field is applied.The silicate phase is introduced through the immersion of a freestanding hydrogel monolith in neat tetramethylorthosilicate (TMOS). Hydrolysis and condensation occurs as the TMOS infuses the hydrogel and reacts with water trapped in the voids. After a period of 24 h a hard solid white monolith, close in size to the hydrogel template, is formed. Calcination under O 2 at 500 8C removes the organic phase leaving a porous silica monolith.Scanning electron micrographs of this material, imaged parallel to the electric field direction (Figure 2 a), show striations oriented in the field direction. No such features are observed when the disordered template is used, which suggests that the channel/hydrogel interface is replicated

ABSTRACT:We report the synthesis of poly N-(2-hydroxypropyl)methacrylamide ordered arrays of fluid filled channels. The polymerization and crosslinking reactions are carried out under the influence of a constant electric field (60 V/cm). A charged comonomer, immobiline (pK 3.6), and porogen, polyethylene glycol (PEG) are added to the pregel solutions. Scanning electron microscopy reveals that the channels have a typical diameter of 2-25 lm and are oriented parallel to the electric field employed during synthesis. The self-organization of channels occurs around an optimal PEG concentration of 8.6 wt/vol %, whereas significantly higher or lower concentrations yield random, isotropic pore structures. Moreover, tensile strength measurements show that the mechanical stability increases with decreasing concentration of PEG. Rheology experiments reveal that the swelling degree of these superabsorbant hydrogels increases with increasing PEG. Possible applications of these microstructured hydrogels as bidirectional scaffolds for regenerating neurons in the injured spinal cord are discussed.