SynopsisA novel two-stage method of preparing 2-hydroxyethyl methacrylate (HEMA) and methoxyphenol or cholorophenol blocked 2,4-tolylene diisocyanate (TDI) was devised. The first stage reaction of TDI with HEMA was carried out in petroleum ether heterogeneously with the precipitation of the intermediate product, monoadduct, in the reaction solution, and followed by a second stage homogeneous reaction of monoadduct with the blocking agent, chlorophenol, or methoxyphenol, in ethyl acetate. In both reactions the inhibitor, chloranil, and the catalyst, dibutyltin dilaurate, were used. A total of eight products were achieved. Results of elemental analyses of these products along with their LC chromatograms, NMR, and IR spectra indicated that these materials were indeed the compounds expected. Testing results of these materials as dental adhesives will be reported in a separate paper.*Deceased.
SynopsisMolecular weight distribution curves have been determined for two samples of polystyrene by fractionating them with a conventional single-stage precipitation technique and followed by measurement of the average molecular weights of the fractions by viscometry. The experimental results obtained were analyzed by the usual method of plotting cumulative distribution curves. Subsequently, the distribution curve for a mixture of aliquots of the two samples was obtained and found to agree with the expected curve, which would be the sum of the curves in the two constituent samples. This finding confirms the internal self-consistency of this method for determining molecular weight distribution curves.
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