SYNTHESIS AND AQUEOUS-SOLUTION CHARACTERIZATION OF DIHYDROPHILIC BLOCK-COPOLYMERS OF METHYL VINYL ETHER AND METHYL TRIETHYLENE GLYCOL VINYLETHER

Water-soluble dihydrophilic AB block copolymers of methyl vinyl ether (MVE) and methyl triethylene glycol vinyl ether (MTEGVE) were synthesi zed by living cationic polymerization, with copolymer molecular weight s in the range 1500-13 900 with fairly narrow molecular weight distrib utions (M(w)/M(n) < 1.29). The MVE block length was fixed at 20 monome r units, and the MTEGVE block length was varied from 2 to 67 units. Aq ueous solutions of these copolymers were studied using dynamic light s cattering, dye solubilization, and turbidimetry to determine the effec t of temperature on micellization and precipitation. The light scatter ing data for all of the block copolymers indicated that they were disp ersed as single chains in water at room temperature, this was further confirmed by aqueous SEC experiments. Turbidimetry experiments showed that phase separation occurred upon heating aqueous solutions of MVE a nd MTEGVE homopolymers to 18 and 83.5 degrees C respectively. Micelles were formed on heating aqueous solutions of these block copolymers ab ove 50 degrees C, which was expected due to the hydrophobic nature of the MVE block at this temperature. Dynamic light scattering studies ga ve hydrodynamic sizes of the block copolymers ranging from 8.1 to 31 n m. Variable temperature H-1 NMR spectroscopy (in D2O) confirmed that t he MVE block forms the micellar core and that micellization was revers ible. The critical micellization temperatures determined by dye solubi lization were found to increase with the MTEGVE content over a relativ ely small temperature range from 27 to 41 degrees C. The cloud points of these copolymers follow a similar trend and increase with the MTEGV E content, covering a wide range of temperatures from 26 to 79 degrees C.