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Anionically Prepared Telechelic Polymers
Published in Eric J. Goethals, Telechelic Polymers: Synthesis and Applications, 2018
David H. Richards, Geoffrey C. Eastmond, Malcolm J. Stewart
The latest recorded work44 was carried out under high vacuum conditions, and the parallel formation of the dimer ketone (͠40%) was observed, but trimer carbinol was not seen. (N.B. The formation of the ketone and the carbinol from the carboxylate can be readily observed by gel phase chromatography (GPC) since their production involves the doubling and tripling of molecular weights, respectively). It was concluded that water has to be present at a stage prior to the total consumption of living polymer to hydrolyze the geminal diol adduct initially formed into the ketone in order to allow subsequent attack to generate the carbinol (Equation 14). This ()
Levoglucosenone-derived synthesis of bio-based solvents and polyesters
Published in Green Chemistry Letters and Reviews, 2023
Cicely M. Warne, Sami Fadlallah, Adrian C. Whitwood, James Sherwood, Louis M. M. Mouterde, Florent Allais, Georg M. Guebitz, Con R. McElroy, Alessandro Pellis
Using water as an anti-solvent gave a higher yield when compared to methanol. However, when the Mn and Mw are considered, although the polymers worked up in CHCl3/H2O have much higher molecular weights than the CHCl3/MeOH polymers, this trend reversed when the work-up was performed in (1). A possible explanation for this trend is that the addition of water to (1) forms a geminal diol through hydration of the ketone moiety (40), which increases the overall polarity of the mixture (41). In our system, the wt% of (1) is approx. 11%, and previous studies have found the majority of (1) to be converted into its geminal diol at this concentration (42). The (1)/H2O antisolvent system is therefore very different when compared to the (1)/MeOH one. When comparing the two solvent systems, a blend of Cyrene and water (in the appropriate ratio) assuming all Cyrene has been converted to the geminal diol has a δP of 38.7 compared to 21.4 for the Cyrene/MeOH system (Table S9). As the Cyrene/H2O system is much more polar, more polymer crashes out, including lower molecular weight oligomers. This both increases dispersity and decreases Mn and Mw for this system. Using a MeOH-based anti-solvent system resulted in higher Mw polymers, which can be seen in Figure 1(c and d), when comparing the Mw of reactions 9 and 11, and reactions 10 and 12. The ODO-based polymer worked-up in (1)/MeOH gave the highest Mn/Mw in this data set; 7.7/17.6 kDa respectively.