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Schmaljohann, D. ; Komber, H. ; Barratt, J. ; Appelhans, D. ; Voit, B.
Kinetics on Nonideal Hyperbranched Polymerizations. 2. Kinetic Analysis of the Polycondensation of 3,5-Bis(trimethylsiloxy)benzoyl chloride Using NMR Spectroscopy

The kinetics of the polycondensation of 3,5-bis(trimethylsiloxy)benzoyl chloride (BTMSBCl)was investigated. 1D and 2D NMR techniques were applied to achieve a complete signal assignment ofthe structural units of the resulting polymer (poly(3,5-dihydroxybenzoic acid), PDHBA), which wasobtained after hydrolysis of the trimethylsiloxy and the acid chloride groups. Furthermore, the diadscould be identified. After quantification of the signals by 13C NMR spectroscopy, a data set of ratios ofstructural units as a function of the conversion had been studied with respect of the kinetics of the systemand their resulting structural composition. Since the data do not follow the ideal conversion dependence,the relative rate constants of the 12 different basic reaction steps were determined by simulation, whichfit the obtained data best. A study of the sensitivity of the reaction curves to changes in the individualrate constants showed large differences and helped to distinguish the importance of the different basicreactions to the overall reaction. One kinetic situation was identified as dominant. The deviations (fromthe ideal conversion dependence) were explained by different electronic effects on the reaction sites causedby the successive substitution of siloxy and benzoyl chloride groups by ester groups on the aromatic ring.Analysis of the data for the diads indicated no further kinetic effect.

Macromolecules 36



Erschienen am
January 2003

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