Silica core-poly

Bershtein, V., Gun ko, V., Egorova, L. et al. 2009. Well-defined silica core-poly(vinyl pyrrolidone) shell nanoparticles Interactions and multi-modal glass transition dynamics at interfaces. Polymer 50 860-871. 

Figure 23 represents the experimental result [130] illustrating the above discussion. In this work, the interfacial interactions and glass transition dynamics were studied for the well-defined silica core-poly(vinyl pyrrolidone) (PVP) shell nanoparticles as model interface-controlled materials. The PVP shell thickness in these particles varied from 1-2 nm (monomolecular layer in a fiattened conformation) up to 10-20 nm. Far- and mid-IR spectra revealed the strong PVP-silica interactions of two kinds hydrogen bonds and soft Lewis acid-base interactions that were maximal for 1-2 nm thick monomolecular PVP shell (20 wt% PVP in the core-shell particles). DSC analysis of the dispersion of activation barriers to segmental motion within the glass transition was performed. 

The Stober method can be used to form core-shell silica nanoparticles when a presynthesized core is suspended in a water-alcohol mixture. The core can be a silica nanoparticle or other types of nanomaterials [46, 47]. If the core is a silica nanoparticle, before adding silicon alkoxide precursors, the hydroxysilicates hydrolyzed from precursors condense by the hydroxide groups on the surface of the silica cores to form additional layers. If the core is a colloid, surface modification of the core might be necessary. For example, a gold colloid core was modified by poly (vinylpyrrolidone) prior to a silica layer coating [46]. 

R. Atkin, M. Bradley, and B. Vincent, Core-shell particles having silica cores and pH-responsive poly(vinylpyridine) shells, Soft Matter 1, 160-165 (2005). 

Fig. 28 Schematic of a poly(lipid)-coated silica nanoparticle. Fluorescent dyes are encapsulated in the sol-gel silica core the nanoparticle is then coated with cross-linked bis-SorbPC doped with...

In another example, BSA, as a model protein, vras entrapped in biodegradable shell crosslinked nanocapsules via layer-by-layer assembly of tertiary amine and hydrazide grafted poly(aspartamide) and carboryl and aldehyde grafted poly(aspartamide) on amino-fiinetionalized silica spheres, by hydrazone crosslinking and with a silica core. Tbe BSA release rate increased significantiy as tbe ambient pH dropped from tbe physiological pH to acidic endosomal pH, and cell experiments showed that the obtained polymerie nanocapsules possessed good uptake properties and biocompatibility. ... 

The variation of the functional monomer concentration is reflected in the PA-FllK spectra of the miniemulsion products. An increasing of the HEMA content in the polymer composite can be seen at the signiflcant carbonyl stretching band at 1600 cm which increased in the spectra from product 1 to product 3 with increasing of the HEMA content in the monomer composition. Nevertheless, next to the typical copolymer bands for poly(S-co-HEMA), signiflcant silica core bands are visible in all spectra. The monomer com-... 

Liu, Y.-L. Li, S.-H., Poly(dimethylsiloxane) Star Polymers Having Nanosized Silica Cores. Macromol. Chem., Rapid Commun. 2004,25,1392-1395. 

Fig. 23 Neat poly(vinyl pyrrolidone) (PVP) and silica core-PVP shell nanoparticles (20PVP/ 80SiO2 composition) with the shell thickness of 1-2 nm (monolayer) [130]. (a) DSC curves of PVP (1) and nanoparticles (2) obtained at the heating rate V = 20°C min. (b) Dispersions of apparent activation energies Q for segmental motion within waterless PVP glass transition as a function of temperature, as determined by DSC for PVP (1) and 20PVP/80SiO2 nanoparticles (2)...

Han, M. G. and Foulger, S. H. (2004) Preparation of poly(3,4-ethylenedioxythiophene) (jjedot) coated silica core-shell particles and pedot hollow particles. Chem. Comm., 2154—5. 

Preformed polymers can also be employed to prepare imprinted core-shell particles [143]. The group of Chang recently prepared a poly(amic acid) bearing oestrone as a template molecule covalently bound to the polymer through a urethane linker (see Fig. 2). A layer of this polymer was subsequently deposited on silica particles (10 pm diameter) prefunctionalised with amino groups at their surface. Thermal imidisation of the polymer yielded finally a polyimide shell (thickness about 100 nm) on the silica particles. Subsequent template removal yielded the imprinted cavities, which exhibited selective rebinding of oestrone in HPLC experiments. 

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