Preparation of Monodisperse Porous Silica Particles Using Poly(Glycidyl Methacrylate) Microspheres as a Template

Monodisperse Porous Silica/Polymer Nanocomposite Microspheres with Tunable Silica Loading, Morphology and Porosity

Hybrid organic/inorganic nanocomposites combine the distinct properties of the organic polymer and the inorganic filler, resulting in overall improved system properties. Monodisperse porous hybrid beads consisting of tetraethylene pentamine functionalized poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) particles and silica nanoparticles (SNPs) were synthesized under Stoeber sol-gel process conditions. A wide range of hybrid organic/silica nanocomposite materials with different material properties was generated. The effects of n(H₂O)/n(TEOS) and c(NH₃) on the hybrid bead properties particle size, SiO₂ content, median pore size, specific surface area, pore volume and size of the SNPs were studied. Quantitative models with a high robustness and predictive power were established using a statistical and systematic approach based on response surface methodology. It was shown that the material properties depend in a complex way on the process factor settings and exhibit non-linear behaviors as well as partly synergistic interactions between the process factors. Thus, the silica content, median pore size, specific surface area, pore volume and size of the SNPs are non-linearly dependent on the water-to-precursor ratio. This is attributed to the effect of the water-to-precursor ratio on the hydrolysis and condensation rates of TEOS. A possible mechanism of SNP incorporation into the porous polymer network is discussed.

Synthesis and application of 5 μm monodisperse porous silica microspheres with controllable pore size using polymeric microspheres as templates for the separation of small solutes and proteins by high-performance liquid chromatography

High-performance liquid chromatography (HPLC) is a powerful tool to separate and analyze complex samples. Monodiseperse porous silica microspheres (MPSMs) have been widely used as column packings in HPLC. However, synthesis of MPSMs with controllable sizes of both particles and pores for the separation of small solutes and proteins in HPLC still remains a challenge. In this paper, an effective and facile approach to prepare MPSMs with controllable particle size and pore size by using porous polymer microspheres as templates is presented. By employing porous P_GMA/EDMA microspheres as templates and tetraethyl orthosilicate (TEOS) as the silica source, 5 μm MPSMs with tunable pore sizes were synthesized successfully. The as-prepared MPSMs were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), dynamic laser scattering, and mercury intrusion porosimetry. The results indicated that the MPSMs obtained retained the original size of the polymer templating particles and calcination caused almost no shrinkage. Furthermore, the effects of the pore size of polymer template microspheres, different amino-functionalizations of P_GMA/EDMA microspheres and the mass ratio of P_GMA/EDMA microspheres/TEOS on the pore size of MPSMs were carefully studied. The results indicated that the pore size of MPSMs was adjusted from 20 to 69 nm by controlling the pore size of the polymer microspheres and the mass ratio of P_GMA/EDMA microspheres/TEOS in the sol-gel process. In addition, the amino-functionalization of P_GMA/EDMA microspheres with different structure-directing agents, such as (3-aminopropyl)triethoxysilane (APTES), trimethylamine hydrochloride (TMA) and tetraethylenepentamine (TEPA), also resulted in MPSMs with the different pore sizes. MPSMs with large pore sizes of more than 30 nm were fabricated by using TEPA-functionalized P_GMA/EDMA microspheres as templates, while with TMA-functionalized P_GMA/EDMA microspheres as templates, MPSMs with pore sizes of approximately 10 nm were obtained. The as-prepared MPSMs were further modified with different silanes, such as C4, C8 and C18, to explore as stationary phases for the separation of proteins and small solutes in reversed phase liquidi chromatography (RPLC). The results illustrated that the baseline separation of 7 kinds of proteins could be achieved based on MPSMs with pore sizes of 30 nm, and 6 kinds of alkyl benzenes and 5 kinds of aromatic alcohol homologs could be separated completely based on MPSMs with pore sizes of 11 nm. This work demonstrated that MPSMs prepared by applying the polymer templating method showed a promising potential applicability in HPLC.