Polystyrene-block-poly(ethylene oxide) copolymers as templates for stacked, spherical large-mesopore silica coatings: dependence of silica pore size on the PS/PEO ratio

Abstract

SummaryLarge-mesopore silica films with a narrow pore size distribution and high porosity have been obtained by a sol–gel reaction of a silicon oxide precursor (TEOS) and using polystyrene-block-poly(ethylene oxide) (PS-b-PEO) copolymers as templates in an acidic environment. PS-b-PEO copolymers with different molecular weight and composition have been studied in order to assess the effects of the block length on the pore size of the templated silica films. The changes in the morphology of the porous systems have been investigated by transmission electron microscopy and a systematic analysis has been carried out, evidencing the dependence between the hydrophilic/hydrophobic ratio of the two polymer blocks and the size of the final silica pores. The obtained results prove that by tuning the PS/PEO ratio, the pore size of the templated silica films can be easily and finely predicted.

An Easy Synthesis for Preparing Bio-Based Hybrid Adsorbent Useful for Fast Adsorption of Polar Pollutants

“…Mesoporous materials, thanks to their large and tunable porosity find potential applications in catalysis, encapsulation of proteins, filtration and separation of large molecules, membrane technology, drug delivery, dosing, sensing, among many others [17,18] Furthermore, their large specific surface area and huge number of adsorbing active sites suggest their possible application as adsorption materials [19].…”

“…Mesoporous γ-Al 2 O 3 has been not only widely applied in all the field mentioned above [17,21,22] but in recent years the chance to synthesize hybrid materials to enhance the useful properties of an oxide opens the way to very interesting opportunities. The literature reports that many oxides have been modified using organic moieties able to enhance the adsorption capacity of the original material.…”

Enhanced γ-phase crystallinity of Al2O3 frameworks at the concave surface of PS-b-PEO templated spherical pores

“…[38][39][40][41][42][43][44] In the case of the preparation of a mesoporous silica (SiO 2 ) film using PS-b-PEO, the resultant size of spherical pores was empirically explained by using PS and PEO lengths ( pore diameter ranging from 4 to 22 nm) 45 and PS/PEO ratios ( pore diameter less than 50 nm). 36 In the latter paper, large mesopores (∼40 nm) were very spherical but the diameter was not uniform and distributed in the range between about ±5 nm. 36 Another significant paper on the fabrication of mesoporous titania films using a number of PS-b-PEO (smaller than 20 nm) has also demonstrated the difficulty in obtaining long-range ordered large mesopores using high-molecular-weight PS-b-PEO.…”

“…This is because the length of the entropy-driven PS core is interrupted by the presence of the PEO unit and the overall pore size strongly depends on the molecular structure of PS-b-PEO like the PS/PEO ratio. 34 In the case of silica films, 35,36 spherical large mesopores are embedded with a long pore-to-pore distance and a tendency that pore size seems to depend on the PS/ PEO ratio has been confirmed using PS-b-PEO. The mesopores are connected by PEO induced micropores.…”

Block copolymers for designing nanostructured porous coatings

“…By coupling the spin-coating deposition technique with the soft-templating approach, mesoporous silica coatings were obtained using PS- b -PEO block copolymers as SDAs [ 103 ]. In this study, by modulating the starting composition (in particular, the hydrophilic/hydrophobic solvent ratio), a transition from stacked spherical pores to worm-like structures to spherical dense particles was reached due to the minimization of the surface free energy [ 104 ]. Analogously as for silica, even titania can be produced with closed spherical pores within the oxidic structures by using high molecular weight PS- b -PEO copolymers (as shown in Fig.…”