Synthesis freeze-drying

Chitosan freeze-dried fleeces support chondrocyte attachment and synthesis of extracellular matrix [344]. Chitosan was used to assist the spontaneous tissue repair of the meniscus [345]. The repair of the cartilage and the prevention of its degradation in osteoarthritis is, however, possible with the association of glucosamine sulfate salt and chondroitine sulfate, the latter being particularly effective [346]. 

Synthesis. Graft copolymer was formed in aqueous solution by ceric-ion-initiated, radical polymerization of monomer on starch. Polymerization was conducted in an inert, atmosphere. Details of the synthesis procedure may be found in references 41 to 43 In recovering the polymer product, freeze drying was used with care since freeze drying produces a more dissolvable and useful product but can degrade polymers with molecular weights of 1 million or more. Poly(starch-g-(1-amidoethylene)) Poly(starch-g-(1-amidoethylene))... 

Oxidation of Anionic Polymers In the Solid State The ability of the macroradical and of the macroions to diffuse In the mixture, and to interreact Is responsible for the secondary products formation coupling reaction and alcoholate synthesis. To prevent the diffusion phenomenon, we have carried out the deactivation In the solid state. The living polymers have been prepared In benzene, with or without a solvating agent (THF or TMEDA) and the solution has been freeze dried before the oxygen introduction. The experimental results are collected in Table VII. 

Kondou, S., Kakojawo, K., Sasaki, Y. Synthesis of PbfZpJTij J03 by freeze drying method. Nippon Kagaku Kaishi (7), 753-758,1990... 

Fukasawa, T., Ando, M., Ohji, T. Fabrication of porous ceramics with complex pore structure by freeze drying process. Ceram. Trans. 112, Innovative Process-ing/Synthesis Ceramics, Glasses and Composites IV, 217-226, 2001... 

Sofie, S., Dogan, F. Ceramic shape forming by freeze-drying of aqueous and non-aqueous slurries. Ceram.Trans. 108, Innovative Processing/Synthesis of Ceramics, Glasses and Composites III, 235-243, 2000... 

Many methods have been used for synthesis of nano-sized particles vapour transport [2], precipitation of homogeneous solution [3], synthesis by sol-gel process [4], freeze-drying... 

E. Bermejo, T. Becue, C. Lacour, M. Quarton, Synthesis of nanoscaled iron particles from freeze-dried precursors, Powder Technol. 94 (Issues 1) (1997) 29-34. 

Solid state reactant Thermal decompositions of a solid Oxidation or reduction of a solid Precipitation Solution heating or cooling Evaporative salting-out Chemical reaction with insoluble product Hydrothermal synthesis Forced insolubility Dissolution reprecipitation Evaporative Condensation Gas phase reaction with solid product Thermal decompositions Oxidation or reduction reactions Combination reactions with a solid product Solvent removal Spray drying Freeze drying Spray roasting Sol-gel synthesis Melt solidification... 

FIGURE 4.1 Scheme of the freeze-drying synthesis process. 

One of the most practical modifications of freeze-drying synthesis is the cryoimpregnation process. This process is often considered as an independent synthesis technique. In this case, the object of freeze-drying is a porous matrix of fibers or powders soaked/wetted with a solution of microcomponents and frozen by fast cooling. The purpose of the cryoprocessing method in this case is prevention of macro- and microscopic redistribution of the microcomponents within the substrate, which is usually observed during air or thermal drying. 

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