Traditional hydrogels usually possess inferior mechanical properties as well as lacking multi-functionalities. Nano-sized particles/fillers, both inorganic and organic materials, have unique chemical, physical, and biological functions, and have been extensively studied as biomaterials or bio-functional materials. Nanocomposite hydrogels, which combine the advantages of both nano-fillers and hydrogel matrices, may result in improved mechanical and biological properties and find their potential applications in biomedical field. This paper reviews recent developments in the synthesis, preparation, and characterization of nanocomposite hydrogels; their biomedical applications, such as drug delivery matrices and tissue engineering scaffolding materials are also summarized.

Ring-opening polymerization of ⑀-caprolactone was carried out smoothly and effectively with constant microwave powers of 170, 340, 510, and 680 W, respectively, with a microwave oven at a frequency of 2.45 GHz. The temperature of the polymerization ranged from 80 to 210°C. Poly(⑀-caprolactone) (PCL) with a weightaverage molar mass (M w ) of 124,000 g/mol and yield of 90% was obtained at 680 W for 30 min using 0.1% (mol/mol) stannous octanoate as a catalyst. When the polymerization was catalyzed by 1% (w/w) zinc powder, the M w of PCL was 92,300 g/mol after the reaction mixture was irradiated at 680 W for 270 min.

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A mechanically tough biodegradable hydrogel is developed from a single precursor comprising poly(ethylene glycol) and oligo(trimethylene carbonate), where both the crosslink density and swelling properties of the polymer network are independently controlled through M c and hydrophilic-hydrophobic balance. These highly cost effective hydrogels are also biocompatible and can be degraded both hydrolytically and enzymatically.

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