Rigid Macroporous Poly(divinylbenzene) Monoliths with a Well‐Defined Bicontinuous Morphology Prepared by Living Radical Polymerization

Abstract

Monolithic organic polymer gels with a well-defined bicontinuous structure have been synthesized using polymerization-induced phase separation during the 2,2,6,6-tetramethylpiperidin-1-yl oxide (TEMPO)-mediated living radical polymerization [1] of divinylbenzene (DVB). In the field of polymer membranes, separation and ion-exchange resins, porous polymer particles, films, and monoliths are widely prepared by conventional free radical polymerization in which phase-separation or templating methods are utilized to tailor the meso-and macropore structure. [2][3][4][5][6][7][8][9][10][11][12] During the course of conventional free radical polymerization using various monomers and crosslinkers, when a monomer or crosslinker molecule starts to react, it is soon segregated from the solvent by an abrupt increase in the local degree of polymerization (DP) or due to the formation of an intramolecular network (cyclization), and thus phase separation (sometimes termed as "microgel" formation) takes place. [13,14] Although these phase-separation methods yield macroporous structures with a narrow size distribution of pores formed by the interstices between segregated particles, the precise and independent control of pore size and pore volume is rather difficult. The facile and fine control of pore properties has recently become necessary because monolithic porous materials with well-defined pore properties and surfaces have been shown to allow faster transport of liquid and gas molecules; moreover, these structures possess higher mechanical strength [15,16] and are especially suitable as chromatographic separation media, ion exchange resins, [17][18][19] and catalyst supports. [20] As an example of a class of porous materials with a well-defined pore structure, organic-inorganic hybrid macroporous gels based on methylsilsesquioxane have been fabricated by inducing spinodal decomposition (SD) during the sol-gel transition of methyltrimethoxysilane (MTMS), and have found excellent applicability as separation media for high-performance liquid chromatography (HPLC), as reported previously by us [21] and Dong et al. [22] During the polycondensation reaction in the sol-gel system, the trifunctional monomer MTMS becomes insoluble in the polar solvent due to the presence of methyl groups directly attached to the Si atom in these molecules, consumption of polar silanol groups that are formed by the hydrolysis of MTMS (these two factors lower the polarity of the MTMS-derived species), and increase of the DP.[15] Porous organic polymer gels which are easily removed by pyrolysis can also be used as a sacrificial "mold" to prepare porous materials with various chemical compositions. [23,24] Breulmann et al. [23] have reported the use of porous polymer gels as templates, and have successfully prepared replicas of iron and titanium oxides by allowing the corresponding inorganic nanoparticles to swell into the wet polymer gels, followed by removal of the template by thermal decomposition. In addition, carbonized polymer monoliths can be used as...

Facile preparation of a stable and functionalizable hybrid monolith via ring-opening polymerization for capillary liquid chromatography

“…Furthermore, benefiting from the moderate phase separation process of ring-opening polymerization, the hybrid monoliths possess highly ordered 3D skeletal structure, and are promising for separation with ultrahigh column efficiency [22,[28][29][30]. The facile approach is, of course, of interest to develop raw hybrid monoliths with homogeneous microstructure, high robustness and tailorability.…”

Development of Non-Siliceous Porous Materials and Emerging Applications

“…The coarsening process is followed by fragmentation of the minority phase and subsequent restructuring due to minimization of surface energy, which finally results in spherical domains and a continuous matrix (f 32 Owing to recent progressive studies, the concept of polymerization-induced phase separation has expanded into siloxane-based organicinorganic hybrids 33 and even organic polymers. 34 Advances concerning non-siliceous inorganic materials follow.…”

Catalysts Immobilized on Organic Polymeric Monolithic Supports: From Molecular Heterogeneous Catalysis to Biocatalysis

“…A cation-exchange resin was also prepared by grafting 3-sulfopropylmethacrylate to the monolithic surface. [5,[73][74][75] …”