Polymer-particles hybrid layers

Here we describe an example of the fabrication and investigation of smart responsive nanoparticles by grafting block-copolymers. We grafted triblock copolymer of poly(styrene-fc-2-vinylpyridine-fc-ethyleneoxide) (P(S-b-2VP-b-EO) to silica particles 200 nm in diameter (Fig. 18.9). The particles were modified by 11-bromoundodeciltrimethoxisilane (BUDTMS), then the block-copolymer was grafted by a quatemization reaction to the particle surface. The grafting of the block-copolymer to the silica nanoparticles was proved by FTIR using the diffuse reflection technique. Very well-pronounced 

9 Tri-block copolymer grafted to the silica particles via a quaternization reaction between pyridine rings of the central P2VP blocks and 11-bromoundodeciltrimethoxisilane on the silica particle. 

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TEM and ultracentrifuge results showed (see Fig. 16) that this process results in effective encapsulation of the carbon with practically complete yield only rather small hybrid particles, but no free carbon or empty polymer particles, were found. It has to be stated that the hybrid particles with high carbon contents do not possess spherical shape, but adopt the typical fractal structure of carbon clusters, coated with a thin but homogeneous polymer film. The thickness of the monomer film depends on the amount of monomer, and the exchange of monomer between different surface layers is - as in miniemulsion polymerization - suppressed by the presence of an ultrahydrophobe. 

The thickness of the hybrid polymer coating depends on the roughness of the polymer film that is used and the presence and size of anti-block particles on the film. In addition to the planarizing effect in the laminates 4. and 6. (Table 21-4, Fig. 21-22, scheme (c)), it can also be assumed here that there are chemical links to the adjacent AlO layer (see Fig. 21-22, scheme (b)). Thus, synergistic effects can be explained by the chemical and mechanical interactions at possible polymerfilm/hybrid polymer/MeO /hybrid polymer interfaces. 

Meille et al. [127] described in detail a hybrid sol-gel/suspension method for coating silicon structures with alumina. Because the channel sizes were very small, the deposited layers were not to exceed 1 pm in thickness. Therefore, the authors used suspensions with particle sizes in the nanometer range and low concentrations (between 0.5 and 5 wt%). An acidic suspension of boehmite was prepared. The boehmite dissolves partially and forms Al-O-Al polymers, which help to anchor the particles to the surface. The resultant layers were subsequently characterized and impregnated with platinum acetylacetonate. 

On the contrary, particles without pores enable fast, efficient separation of proteins due to the absence of intraparticle diffusion resistance. The absence of pores reduces the available surface area and thereby the loading capacity. Silica- [49] and polymer-based [50] nonporous particles have been applied for biomolecule separations. Also hybrid particles have been described that have a non/porous core and a 0.25-pm porous layer, composed of colloidal silica particles [51]. 

Control over release rates from mesoporous surfactant templated particles has been obtained by several methods. The size and connectivity of the pore system as well as particle size and shape are of prime importance. Simple organic functionalisation on the external and internal surfaces of the particles ° or preparing hybrid particles in thermo-responsive hydrogels, " biodegradable polymers " or collagen " can affect release rates. Polymer layers have also been used to determine entrance of particular species into pores for sensor purposes. 

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