Water-soluble/compatible initiators

In this case, a moderately water-soluble amphiphilic N-vinylcaprolaclam (NVC1) played the role of a fl-unit, and a well-water-compatible N-vinyl-imidazole (NVIAz) served as a P-unil. The polymerization was carried out in a medium of 10% aqueous dimethylsulfoxide (DMSO). The addition of DMSO to the reaction solvent was necessary because of insufficient NVC1 solubility in pure water. It was also shown that in this solvent mixture, the NVCl-homopolymers and NVCl/NVIAz-copolymers retained their LCST-behaviour [26,28]. Hence, the DMSO in the reaction solvent did not significantly suppress the hydrophobic interactions of the NVC1 units. The polymerization was initiated by the redox system (N,N,N, N -tetramethylethylenediamine (TMEDA) + ammonium persulphate (APS)) and was carried out at 65 °C (1st step). This condition was very important, since admittedly the temperature was higher than the phase separation threshold of the reaction bulk when the polymeric products were formed that is, under these thermal conditions, hydrophobically-induced folding as the NVCl-blocks appear was ensured. After completion of the reaction, the... 

Among other methods to render surfaces of implanted materials bio-compatible, in particular to prevent them from initiating blood clotting, one may activate the surfaces by radiation and then graft water soluble, or negatively charged, polymers onto the active sites. 

In the batch process low-water-solubility monomers are emulsified in water by water-soluble surfactants, purged and heated at the initiation temperature (for energy saving this is usually lower than the reaction temperature to benefit from the reaction exotherm) and the initiator added. Temperature is then maintained for the reaction period, which can range from 1 to 24 h. Reactions are driven to the maximum conversion compatible with the system and the residual monomer and other volatile compounds are removed either by stripping or by chemical treatment. 

Liska reported preparation of water-soluble photoinitiators that contain carbohydrate residues as well as copolymerizable derivatives of the carbohydrate residues. These materials consist of alkylphenones, benzophenones and thioxanthones. To these compounds were attached carbohydrates like glucose, cellobiose, and 1-amino-1-deoxy-D-glucitol. In addition selected initiators were reacted with methacryloyl chloride to form polymerizable photoinitiators. The glucose modified photoinitiators were claimed to yield the best results with respect to compatibility with resins, reactivity and gel content. ... 

Vis, pour points, water solubilities and oil-compatibilities are produced by choosing the proper initiators, monomers, reaction conditions and post treatments. The reaction is highly exothermic (22.6 kcal/mole) and heat removal is important to avoid side-reactions or broadening of the product molecular weight distribution. 

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