Transformations and enhanced long-range ordering of mesoporous phenolic resin templated by poly(ethylene oxide-b-ε-caprolactone) block copolymers blended with star poly(ethylene oxide)-functionalized silsesquioxane (POSS)

Abstract

In this study, we prepared ordered mesoporous phenolic resins templated by poly(ethylene oxide)-b-(3caprolactone) (PEO-b-PCL) diblock copolymers blended with a star PEO octa-functionalized polyhedral oligomeric silsesquioxane (PEO-POSS) homopolymer. Increasing the PEO-POSS content, and thereby increasing the PEO-to-PCL ratio in the template film, allowed us to tune and enhance the long-range order of the mesoporous phenolic resin. The increased pore size and the more ordered structure were accompanied by a narrower pore size distribution. In addition, we observed an orderedto-ordered mesophase transition, from a bicontinuous gyroid to a hexagonally packed cylinder structure, upon blending with the star PEO-POSS homopolymer. We anticipate that this approach could be extended to the preparation of other large-pore, long-range-ordered mesoporous materials, such as silica and other metal oxides.

Fabrication and Characterization of Inorganic Silver and Palladium Nanostructures within Hexagonal Cylindrical Channels of Mesoporous Carbon

“…To prepare the mesoporous carbon, we first used a simple ring-opening polymerization (ROP) to synthesize an amphiphilic diblock copolymer PEO-PCL, with a specific weight ratio of each segment (EO 114 CL 84 ; NMR M n = 14,600; PDI = 1.31) [5,6]. Next, we combined the EO 114 CL 84 , phenolic resin, and PEO-POSS at a unique weight ratio (EO 114 CL 84 :phenolic resin:PEO-POSS = 50:50:22) and subjected the mixture to EISA and calcination steps to fabricate an hexagonal cylindrical mesoporous phenolic resin [9]. Finally, we carbonized our hexagonal cylindrical mesoporous carbon under a N 2 atmosphere.…”

“…Prior to its development, the pore sizes of mesoporous carbons were limited to approximately 5-10 nm as a result of the need for copolymer templates of low molecular weight [13,14]. The EISA method made it feasible to regulate pore structures and pore sizes and allowed the preparation of various mesoporous materials from water-insoluble systems, including mesoporous silicas [2,7,8,10,[15][16][17][18], mesoporous resins [3,6,9,11], mesoporous TiO 2 [19][20][21], and mesoporous carbons [2,4,12,16,[22][23][24]. The typical procedure used to prepare ordered mesoporous carbons, so-called "template synthesis" [25][26][27][28][29][30], involves the use of mesoporous silicas as hard templates, impregnation of carbon precursors into their mesochannels, carbonization under an inert gas, and finally dissolving the hard template of the "ordered mesoporous silica" through etching in HF (aq) .…”

“…Evaporation-induced self-assembly (EISA) has been developed aggressively as a strategy for the fabrication of mesoporous nanostructures because of its broad applicability to soft templating using various block copolymer templates [1][2][3][4][5][6][7][8][9][10][11][12]. Prior to its development, the pore sizes of mesoporous carbons were limited to approximately 5-10 nm as a result of the need for copolymer templates of low molecular weight [13,14].…”

“…Moreover, we blended in the star octakis-PEO-functionalized polyhedral oligomeric silsesquioxane (PEO-POSS) to induce higher ordering of the mesostructures as well as mesophase transformations of the mesoporous phenolic structures [9]. In this present study, we used a mesoporous phenolic resin possessing a hexagonal cylindrical structure as the carbon precursor for the preparation of mesoporous carbon under a N 2 atmosphere at 800 °C; subsequently, we employed this product and a simple incipient wetness strategy to fabricate Ag/mesoporous carbon and Pd/mesoporous carbon nanocomposites (Scheme 1).…”

In Situ Monitoring of the Reaction‐Induced Self‐Assembly of Phenolic Resin Templated by Diblock Copolymers

“…In previous studies, we used evaporation‐induced self‐assembly (EISA), with double‐crystalline poly(ethylene oxide‐ block ‐ε‐caprolactone) (PEO‐ b ‐PCL) diblock copolymers as templates and HMTA as the crosslinking agent, to prepare a series of mesoporous phenolic resins . In these phenolic resin/PEO‐ b ‐PCL systems, we observed, using small‐angle X‐ray scattering (SAXS), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy, an interesting relationship between the transformation of the mesophase and the degree of competitive hydrogen bonding.…”