Poly -grafted silica

In a comparative study, poly(7-oxanorborn-5-ene-2,3-dicarboxylic acid)-grafted silica supports, again prepared via a grafting-from approach, possessed better separation behavior than the analogous coated separation media [45]. 

Fig. 12.1.1 Dependence of order parameter, S. of the secondary polymer, spin-labeled poly (methyl methacrylate) (PMMA) and polystyrene (PST), bound to poly(maleic anhydride—styrene )-grafted silica on hexane content in ethyl acetate-hexane cosolvent. Numbers in parentheses are number average molecular weight of the secondary polymer. (From Ref. 48.)...

Polymer-grafted silica (SiO2) particles represent one of the most popular colloidal systems with tunable interactions. Ilie chains of choice were mainly polystyrene, poly(dimethyl siloxane), poly(butyl methacrylate), and n-octadecyl or stearyl alcohol. Chain grafting provided the means to tailor the colloidal particle behavior from hard to soft, as well as introduce attractions in a controlled way by varying the temperature or adding non-absorbing polymer depletant [44,95-112]. 

The first successful result was seen in the grafting of poly(octadecyl acrylate) onto silica and its application for separation of PAHs in a reversed phase mode. The polymer is obtained by telomerization of octadecyl acrylate, initiated with 3-mercaptopropyltrimethoxysilane (Fig. 1). The following immobilization is carried out by mixing with porous silica in a suitable solvent. The resultant polymer-grafted silica shows, not only extremely high separation of PAHs, but also specific temperature dependency on the selectivity, which is induced by an ordered-to-disordered transition of the grafted polymer. The detail is described later. 

Poly(methyl acrylate)-grafted silica (Sil-MA, ) showed unexpectedly unique selectivity in a reversed phase mode. The unusual nature of Sil-MA is emphasized by Fig. 2. Octadecylated silica shows a good linearity in the log -log P plots (Fig. 2a), indicating that the elution order is understandable by molecular hydrophobicity of solutes. On the other hand, Sil-MA provides no similar result. As shown in Fig. 2b, it seems to show that Sil-MA , instead, recognizes the molecular size (i.e., the number of the... 

Similar specificities in HPLC have been realized with poly(4-vinylpyridine) and poly(acrylonitrile). The similarity of these polymers can be characterized by the fact that their residual groups include locally polarized moieties with vr-electrons. Here, their uniqueness is summarized through the results of poly(4-vinylpyridine)-grafted silica (Sil-VP ) Sil-VP is less sensitive for molecular hydrophobicity of solutes, as shown in a typical chromatogram of Fig. 4A. This is proof of a great difference from ordinary ODS. On the contrary, higher retention and selectivity (Fig. 4C) are observed for PAHs or tt-electron-containing substances, especially sensitive for difference of the molecular planarities of solutes... 

When poly(L-alanine)-grafted silica is applied for separation of PAHs in a reversed phase mode, we can encounter various specific selectivities. For example, 0=10.4 was obtained for a mixture of p- and o-terphenyls, while a= 1.5 in ODS. Both p- and o-terphenyls possess the same numbers in carbon atoms and rr-electrons, but the molecular planarity is entirely different. As indicated in the Corey-Pauling-Koltun (CPK) models of Fig. 7A,p-terphe-nyl is a little twisted (almost planar), but more slender (linear) than o-terphenyl. No similar enhancement of the selectivity is observed in poly(L-leucine)- and poly(L-phenylalanine)-grafted silica. These polypeptides show, rather, similarity to ODS e.g., 0=1.7 in poly(L-leucine)-grafted silica. 

Analytical methods for phospholipid and glycolipid classes by normal-phase high-performance liquid chromatography (HPLC) have been incompletely reviewed. Silica columns with evaporative light scattering detection (ELSD) were mostly used. The poly(vinyl alcohol)-grafted silica column with ELSD could be used to separate them, simultaneously. 

This knowledge encourages us to apply biomimetic membranes for molecular recognition systems such as HPLC. However, lipid membrane systems suffer from a serious problem owing to their instability in organic solvents. To overcome this problem, we have reported the use of poly(octadecyl acrylate)-grafted silica (Sil-ODA ) as a lipid membrane analogue for stationary phases in RP-HPLC. Poly(octadecyl acrylate) cannot... 

Fig. 3 (a) Temperature dependencies of the separation factors of cis- and rran -stilbene with columns Sil-ODA (open circles), Sil-MA (solid circles), and ODS (open triangles). Mobile phase methanohwater (70 30). Sil-MA poly(methyl acrylate)-grafted silica, (b) Schematic illustrations of interaction mechanism between solutes and stationary phases. 

Green, D. L. Mewis, J., Connecting the Wetting and Rheological Behaviors of Poly(dimethylsiloxane)-Grafted Silica Spheres in Poly(dimethylsiloxane)... 

Yan S, Yin J, Yang Y, Dai Z, Ma J, Choi X (2007) Stffface-grafted silica linked with L-lactic acid oligomer a novel nanofiller to improve the performance of biodegradable poly(L-lactide). Polymer 48(6) 1688—1694... 

The temperature response of the poly(NIPAAM)-silica matrices depends drastically on the architecture of the grafted polymer molecules. Surface wettability changes dramatically as temperature changes across the range 32-35°C (corresponding to the phase-transition temperature for NIPAAM in aqueous media) for surfaces where poly(NIPAAM) is terminally grafted either directly to the surface or to the looped chain copoljnner of NIPAAM and N-acryloylhydroxysuccinimide which was initially conpled to the surface. The wettability changes for the... 

Scheme 11.5 Schematic preparation of poly(NIPAAm-co-VPBA) grafted silica via surface-initiated atom transfer radical polymerization. (Modified and reproduced from ref. 50 with permission. Copyright 2012, Royal Society of Chemistry.)...

Suzuki, K., Yumura, T., Mizuguchi, M., Tanaka, Y., Chen, C.-W., Akashi, M. (2000). Poly(V-isopropylacrylamide)-grafted silica as a snpport of platinum colloids preparation method, characterization, and catalytic properties in hydrogenation. Journal of Applied... 

Yoshioka H, Mikami M, Nakai T et al. Preparation of poly(N-isopropylacrylamide)-grafted silica gel and its temperature-dependent interaction with proteins. Polym Adv Technol 1995 6 418-420. 

Hyperbranched poly(amidoamine)- " " grafted silica nanoparticle... 

Ukaji, M Takamura, M Shirai, K Yamauchi, T. Tsubokawa, N. (2008). Curing of Ep>oxy Resin by Hyp>erbranched Poly(amidoamine)-grafted Silica Nanop>articles and Their Properties. Polymer Journal, 40,607-613... 

Another interesting approach for the elaboration of ionosilica stationary phases consists in the formation of poly(ionic liquid) (PIL)-grafted silica phases. Poly(l-allylimidazole)-grafted silica appeared as a versatile stationary phase for... 

FIG. 18 SEC calibration curves for poly(vmylpyrrolidone)-grafted silica resins (from Ref. 85). Resins N4000-10 (VP 30%), N4000-10 (VP10%), and NlOOO-10 (VP 5%) have native pore diameters of 4000, 4000, and 1000 A, respectively, and were prepared with initial monomer concentrations of 30, 10, and 5% by volume, respectively. 

Park SY, Kim SG, Chun JH, Chun BH, Kim SH (2012) Fabrication and characterization of the chlorine-tolerant disulfonated poly(arylene ether sulfpolyamide-grafted silica composite reverse osmosis membrane. Desalin Wato Treat 43 221-229... 

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