Kamlett-Taft

The kinetics of the Diels-Alder reaction between cyclopentadiene and N-n-butyl-maleimide in mixtures of water with MeOH, MeCN, and poly(ethylene glycol) have been investigated. The results were analysed using the Abraham-Kamlett-Taft model. 

A recent study of the effects of molecular solvents on the nr value has shown it to be correlated with the Kamlett-Taft tz and a scales (see below), and so it is thought to arise from a combination of hydrogen bond donation and dipolarity and polarizability effects [14]. 

Polarity varies widely from one polymer to the next. PDMS has a dielectric constant of only 2.8 [13], meaning that its polarity is close to that of toluene. Solid PEG has a Kamlett-Taft k (polarity/polarizability) value of 0.86 and an Ej(30) value of 45.7 [19], The r(30) value implies a polarity comparable to MeCN or DMSO while the n value is surprisingly high for an entirely saturated structure. Ohno and Kawanabe showed that the Ej(30) of a polyether increases with molar mass and calculated that the E-j-(30) values of PEG and PPG with infinite chain lengths would be 46.6 and 38.5 kcal mol [20]. Thus PPG is significantly less polar, matching the polarity of butyl acetate. 

Table 4 contains a sutrutiary of the reported polarity solvent parameters for PILs, along with comparison values of water and representative values for molecular solvents and AILs. The solvent paramters within the table consist of the Bt(30) scale, determined from Reichardt s dye, Bt, where that scale has been normalized so that water has a value of 1, and the Kamlett—Taft parameters for dipolarity/ polarizability, it, the hydrogen bond donating ability, a, and the hydrogen bond accepting ability, /3. 

---