Polymeric Crystallization Inhibitors

Specifically, the influence of biodegradable, environmentally friendly carboxyl-ated polysaccharide additives, such as carboxymethyl inulin (CMI), has been used to delineate the crystallization kinetics of calcium oxalate. The retardation in crystal growth is controlled by the carboxylation degree of CMI and its concentration [96]. CMI is produced by chemical reaction of the biopolymer inulin [97]. Inulin (Fig. 5.8) 

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If a crystallization-inhibitory polymer is incorporated into the amorphous solid dispersion, the in vivo precipitation may be delayed or completely eliminated, resulting in much improved oral absorption. It is ideal if the polymeric carrier can function as a precipitation (crystallization) inhibitor during in vivo dissolution (Zhang et al. 2009). 

Polymerization Exothermic reaction Catalyst Lack of inhibitor Crystallization ... 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials May ignite combustible materials such as wood Stability During Transport Heat-and-shock-sensitive crystals may separate at very low temperature during transport Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

A kinetic inhibitor is a polymeric chemical that, when added to a production stream, will not change the hydrate formation temperature but will delay the growth of hydrate crystals. These chemicals are polymeric... 

Inhibitors are usually added to butadiene and acrolein to prevent polymerization, but the system is not foolproof. Several runaways have occurred in tank trucks or tank cars containing acrolein. As it cooled, some of the liquid crystallized, leaving the inhibitor in solution. In other cases impurities have been left behind in the bulk liquid, and their concentration has risen sufficiently to start a runaway. 

While the x-ray structure of native Factor Xa has been reported [4] the nature of its crystal packing, specifically the fact that the active site of one Factor Xa molecule is blocked by the N-terminus of a second resulting in a continuous polymeric structure, apparently has precluded diffusing inhibitors into the preformed crystals to obtain complexes. Complexes with inhibitors cocrystallized with Factor Xa also have not been reported [81]. Thus, efforts to do structure-based design with this enzyme have relied on molecular modeling. 

Bicyclic bridged phosphorinane derivatives can be synthesized by different methods. When phenylphosphine is heated with cycloocta-2,7-dienone to 135 °C in the presence of polymerization inhibitors, e.g. hydroquinone, and the double Michael addition product is oxidized, the two crystalline syn and anti isomers (total yield 48-59%) are isolated. Separation by crystallization gives the pure compounds which can in turn be transformed at the carbonyl or the phosphorus group (equation 10) (75T33,76JOC589). 

Weissbuch, 1. Zbaida, D. Addadi, L. Leiserowitz, L. Lahav, M. Design of polymeric inhibitors for the control of crystal polymorphism - induced enantiomeric resolution of racemic histidine by crystallization at 25 degrees. J. Am. Chem. Soc. 1987,109 (6), 1869-1871. 

Materials. Lauryl acrylate was freed of inhibitor by three separatory funnel extractions with 5/f sodium carbonate solution, three deionized water washings, followed by three crystallizations from methanol. Residual methanol and water were removed by 24 hour sparging with nitrogen at room temperature. Both original (inhibited) and purified lauryl acrylate (LA) were polymerized. 

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