Solvent gel

Molecular weights of PVDC can be determined directly by dilute solution measurements in good solvents (62). Viscosity studies indicate that polymers having degrees of polymerization from 100 to more than 10,000 are easily obtained. Dimers and polymers having DP < 100 can be prepared by special procedures (40). Copolymers can be more easily studied because of thek solubiUty in common solvents. Gel-permeation chromatography studies indicate that molecular weight distributions are typical of vinyl copolymers. 

ONp Melting properties in different solvents Gel chromatography X-ray diffraction studies,... 

The spiropyrans are not photochromic in the solid state but do exhibit photochromic behavior when dissolved in any of the following solvents, gels, films, plasticized resins, and plastic solids. 

Solvent Gel time (min) Particle size (nm) Surface area (mVg)... 

Khandekar, N., V. Dorge, H. Khanjian, D. Stulik, and A. de Tagle, Detection of residues on the surfaces of objects previously treated with aqueous solvent gels, in ICOM Committee for Conservation, 13th Triennial Meeting, Rio de Janeiro, September 22-27, 2002, pp. 352-359. 

Since they are open systems that can exchange chemical species with their surrounding solvent, gels can also play the role of chemical reactors. In this framework, the design of open spatial gel reactors has allowed well controlled experimental studies of chemical patterns such as chemical waves or Turing structures (2). They are made of a thin film of gel in contact with one or two continuous stirred tank reactors that sustain controlled nonequilibrium conditions. 

Nafion is the leader of perfluorosulphonic proton conductors. Produced by Dupont de Nemours, it is commercially available in different forms homogeneous or reinforced membranes, powders, tubes and solutions. From solutions of perfluorosulphonic acid or salt in organic solvents, gels and films can also be made. From Nafion , many kinds of composite material may also be prepared either by including small, dispersed particles inside the polymeric phase or by using it to coat solid electronic conductors. The adhesive power of this material is important when it is maintained in contact with a wide variety of supports. 

Dissolving the PHB in 1,2-dichloroethane Solid gel prepared by evaporation of part of the solvent Gel extrudable at about 170°C Consequently processed in three stages PHB concentration as high as possible [205]... 

SEC columns separate molecules according to their hydro-dynamic volumes in solution. In an ideal experiment, only entropic effects play a role, and molecules are solely separated by size. However, in most cases, enthalpic processes owing to polymer gel-polymer solute interactions, in addition to solvent-polymer and solvent-gel matrix interactions, have to be taken into account, because they affect the values of the sample elution volumes.When these non-exclusion secondary mechanisms are present, mainly as adsorption, the polymer-polymer interactions increase and shift the retention volumes of solute macromolecules to higher values. Both the exclusion of macromolecules and the interaction with the column packing are affected by the sample concentration or by the eluent applied, which is... 

The PVC gel network was studied as a function of polymer crystallinity and polymer-solvent interaction. Using a range of solvents, a correlation between gel-forming ability, as judged by indentation-modulus values, and solubility parameter was observed. Twin maxima either side of the minimum corresponding to the d-value for PVC confirmed that medium solvents gel PVC most readily. Good solvents do not permit sufficient interchain contact to produce... 

Grubbs and coworkers [6] studied ROMP of strained [4]ferrocenophanes as a plausible route to poly(ferrocenylene-divinylene) and related poly(ferrocenylenebutenylene) (Scheme 12.2, R = H) employing a W-initiator. The obtained polymers (R = H) with n> 10 displayed somewhat limited solubility in common organic solvents. Gel permeation chromatography (GPC) analyses of the CH2Cl2-soluble fractions showed oligomeric structure of these products with chain lengths of circa 10. 

Khanjian, H., Stulik, D., Miller, D. (2004). Research into solventresidues. In V. Dorge (Ed.), Solvent gels for the cleaning of works of art The residue question. The Getty Conservation Institute. 

Stavroudis, C., Doherty, T. (2007). A new approach to cleaning. 11. Extending the modular cleaning program to solvent gels and free solvents, part 1. Western Association for Art Conservation Newsletter, 29(3), 9-15. 

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