Robson F. Storey

Quantifying hydroxyl functionality of telechelic poly(ethylene ether carbonate) diols

SummaryA Fourier transform infrared-based method for quantification of hydroxyl functionality was developed and applied to several commercial poly(ethylene oxide) samples of known difunctionality and several experimental poly(ethylene ether carbonate) (PEEC) samples. The PEEC prepolymers were synthesized by ring-opening bulk polymerization of ethylene carbonate using dibutyltin diacetate, dibutyltin dilaurate or dibutyltin dimethoxide as catalysts. Absorption measurements were made of a sterically favored five-membered hydrogen-bonded ring, containing the terminal hydroxyl group, which forms under dilute solution conditions in methylene chloride. Calibration of the method was obtained by measuring the absorption of known concentrations of a model compound. The purified polymers were shown to be hydroxy-terminated using the infrared method in conjunction with measurements of number average molecular weight.

Sulfonation of chlorine-containing polymers: Sulfonation of various model tert-alkyl chlorides

Summarytert-Alkyl chlorides of the structure R-C(CH3)2Cl, where R-methyl, ethyl, tert-butyl, and neo-pentyl, were reacted with a stoichiometric quantity of acetyl sulfate at room temperature in methylene chloride diluent. Reaction conversion was monitored as a function of time using 1H NMR; structure of the sulfonated products was characterized using 1H and 13C NMR. Reactivity toward sulfonation increased with increasing size of the R group. In all cases the structure of the products was the same as would be expected from sulfonation of the olefin which results from dehydrochlorination of the tert-chloride. The observed behavior was consistent with a mechanism involving dehydrochlorination followed by addition of SO3 to yield a zwitterionic intermediate. Depending upon structure, the zwitterion may either eliminate a proton to form one or more isomeric β,γ-unsaturated sulfonic acids, or it may rearrange to form a five-membered γ-sultone. This chemistry, which is particularly useful in the synthesis of ionomers, represents a direct route to alkyl sulfonic acids when the alkyl halide is the natural starting point in the synthesis.