This article reviews the recent advances and challenges in the preparation of polymer/inorganic hybrid nanoparticles. We mainly focus on synthetic strategies, basing our classification on whether the inorganic and the polymer components have been formed in situ or ex situ, of the hybrid material. Accordingly, four types of strategies are identified and described, referring to recent examples: (i) ex situ formation of the components and subsequent attachment or integration, either by covalent or noncovalent bonding; (ii) in situ polymerization in the presence of ex situ formed inorganic nanoparticles; (iii) in situ precipitation of the inorganic components on or in polymer structures; and (iv) strategies in which both polymer and inorganic component are simultaneously formed in situ.

We report the synthesis of ceria/polymer hybrid nanoparticles and their use as effective supported catalysts for the hydration of nitriles to amide, exemplified with the conversion of 2-cyanopiridine to 2-picolinamide. The polymeric cores, made of either polystyrene (PS) or poly(methyl methacrylate) (PMMA), are prepared by miniemulsion copolymerization in the presence of different functional comonomers that provide carboxylic or phosphate groups: acrylic acid, maleic acid, and ethylene glycol methacrylate phosphate. The functional groups of the comonomers generate a corona around the main polymer particle and serve as nucleating agents for the in situ crystallization of cerium(IV) oxide. The obtained hybrid nanoparticles can be easily redispersed in water or ethanol. The conversion of amides to nitriles was quantitative for most of the catalytic samples, with yields close to 100%. According to our experimental observations by high-performance liquid chromatography (HPLC), no work up is needed to separate the product from unreacted substrate. The substrate remains absorbed on the catalyst surface, whereas the product can be easily separated. The catalysts are shown to be recyclable and can be reused for a large number of cycles without loss in efficiency.

Reactive compatibilization was used to control and stabilize 20-30 wt% poly(dimethylsiloxane) (PDMS) dispersions in nylon 6 (PA6) and poly(styrene) (PS), respectively. The effect of the type of reaction (amine (NH,)/anhydride (An), NH,/ epoxy (E) and carboxylic acid (COOH)/E) on the morphology was studied with electron microscopy. PS and PDMS have mutual solvents and thus it was possible to use gel permeation chromatography (GPC) to determine the concentration of block copolymer in PS/PDMS blends. Reactive blending of PA6 with difunctional PDMS-(An], did not decrease the PDMS particle size compared to the non-reactive blend (-10 pm). Particle size decreased significantly to about 0.5 pm when PA6 was blended with a PDMS containing about 4 random An groups along the chain. For the PS/PDMS blends, GPC revealed that the NH2/An reaction formed about 3940 block copolymer and produced stable PDMS particles -0.4 pm. No reaction was detected for the PS-NH,/PDMS-E blend and the morphology was coarse and unstable. Also, PS-NH,/PDMS-An reactivity was lower compared to other systems such as PS/poly(isoprene) and PS/poly(methylmethauylate) using the same reaction. This was attributed to the relatively thinner PS/PDMS interface due to the high PS/PDMS immiscibility.

Metal oxide/polymer hybrid nanofibers are prepared by in situ formation of metal oxide nanoparticles on surface-functionalized polymer fibers.