M. Jayakannan, Joost L. J. Van Dongen, Girish Ch. Behera and S. Ramakrishnan
An AB2 monomer, 1-(2-hydroxyethoxy)-3,5-bis-(methoxymethyl)-2,4,6-trimethylbenzene, was synthesized from mesitol and melt-polycondensed in the presence of an acid catalyst via a transetherification process at 145–150 °C to yield a soluble, moderately high molecular weight hyperbranched polyether (weight-average molecular weight = 64,600, weight-average molecular weight/number-average molecular weight = 5.2). The origin of the broad molecular weight distribution, which could either be intrinsic to such hyperbranched structures or be due to structural heterogeneity, was further probed by the fractionation of the samples by size exclusion chromatography and by the subjection of each fraction to matrix-assisted laser desorption/ionization time-of-flight mass spectral analysis. The mass spectral analysis suggested the presence of two primary types of species: one corresponding to the simple branched structure and the other to macrocyclics. Interestingly, from the relative intensities of the two peaks, it was apparent that cyclization became favorable at higher conversions in the melt transetherification process.