Polymer-grafted silica

Preparation and Stability of Polymer-Grafted Silica Dispersions... 

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]. 

FIGURE 6.8 (a) Schematic illustration of the procedure for the synthesis of polymeric capsules based on surface-initiated RAFT polymerization using silica nanoparticles as templates, (b) TEM image of polymer grafted silica nanoparticles, (c) SEM and (d) TEM images of the synthesized polymeric capsules. Source Huang et al. [15]. Reproduced with permission of American Chemical Society. 

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. 

Fukui, M. Shundo, A. Nakashima, R. Takafuji, M. Akasaka, K. Ohrui, H. Diara, H. Chromatographic separation of diastereomers using the comb-shaped polymer-grafted silica. International Chemical Congress of Pacific Basin Societies, Hawaii, USA, Decl5-20, 2005 Vol. 

Ueno K, Inaba A, Kondoh M, Watanabe M (2008) Colloidal stability of bare and polymer-grafted silica nanoparticles in ionic liquids. Langmuir 24 5253—5259... 

S.P. Armes, T. von Werne, T.E. Patten, Synthesis of well-defined polymer-grafted silica particles by aqueous ATRP, Langmuir 2001, 37,4479-4481. 

DEA Spherosil M Polymer-grafted silica 40-100 Diethyl aminoethyl n.a. n.a. n.a. Pore size (1000 A) BioSepra... 

DEA Spherosil LS Polymer-grafted silica 100-300 Diethyl aminoethyl n a. 

Browne, T.E., and Cohen, Y., Polymer-grafted silica A screening system for polymeric adsorption resin development, Ind. Eng. Chem. Res., 32(4), 716-725 (1993). 

We have reported the scale-up synthesis of polymer-grafted silica nanopartide in a solvent-free dry-system. In solvent-free dry-system, the isolation and purification after the graft polymerization was easily achieved, because untreated monomer can be removed under high vacuum (Tsubokawa, 2007). 

As mentioned above, the radial graft polymerization of vinyl monomers onto silica nanoparticle and carbon black surface was initiated by surface azo groups previously introduced onto the surface, and we can obtain the corresponding polymer-grafted silica nanoparticle and carbon black by the "grafting from" process (Tsubokawa et al., 1990 Fujiki et al., 1990 Tsubokawa et al., 1992a). 

Scheme 2. General structures of polymer grafted silica stationary phases for HPLC.

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