Medium chain configuration, influence

In interpreting the influence of the medium on chain configuration of the polymers, the medium must be specified as a three-component system polar monomer, polar solvent, nonpolar solvent. 

The elastic repulsion. Once the interpenetrational-plus-compressional domain is entered, not only must the mixing contribution to the steric repulsion be considered but so too must the elastic contribution. As the second particle approaches closer than the span of the stabilizing chains, the chains are compressed and so must lose configurational entropy. This is the origin of the elastic repulsion. The elastic repulsion is relatively insensitive to the solvency of the dispersion medium, being influenced by its nature only insofar as the solvency affects the chain conformation. 

The functions of chiral drugs in human body are closely related to their configurations. It has been reported that the R- and S-isomers of ibuprofen have quite different biological activities and toxicides. So it is imperative to prepare enan-tiomerically pure ibuprofen. Song el al. conducted a study on the lipase-catalyzed esterification of racemic ibuprofen with octanol in AOT reverse micelles [108,109] and found that the esterification is enantioselective and the main product is the corresponding S (-H)-ibuprofen ester, with the conversion yield and the enantiomer excess being about 36% and 0.9732, respectively. The water content and the concentration of AOT in the medium affected the conversion yield, but they had little influence on the enantiomeric excess (Table 15.7). Also, it was found that the chain lengths of alcohols affected both the rate of the reaction and the enantiomeric excess of the products. 

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