Journal of the Chinese Institute of Chemical Engineers, Vol.33, No.6, 599-608, 2002
Effect of block size and sequence on the micellization, hydrophobicity, and surface adsorption of ABC triblock methacrylic polyampholytes by isothermal titration calorimetry
The micellization, hydrophobicity, solubilization and surface adsorption of some water-soluble, low-polydispersity, low molecular weight block methacrylic polyampholytes are systematically examined in this study. The polyampholytes were M,2A,2B,2, M36A36B36, A(36)M(36)B(36), A(8)M(12)B(16), A(16)M(12)B(8) and A(10)M(20)B(10), where B is 2-(dimethylamino)ethyl methacrylate (DMAEMA), M is methyl methacrylate (MMA), and A is methacrylic acid (MAA). Isothermal titration microcalorimetry (ITC) was employed to determine the CMC of the polyampholytes in aqueous solution, and the results were compared to the CMC determined by the surface tension and the hydrophobicity specified by the partition between Dextran/PEG two aqueous solution. Moreover, the results of ITC experiments were analyzed to obtain the heat of micellization and the heat of dilution of polyampholytes and micelles. Qualitatively, more hydrophobic polyampholytes correspond to a lower CMC value and less heat of dilution released in both the micelles and monometric solution. The pI value and solvable region of various polyampholytes were also determined in aqueous solutions at different pH values and salt concentrations. Additionally, the adsorption isotherms of the polyampholytes with the anion exchange resin were preformed to study the electrostatic and hydrophobic interactions between the polyampholytes and the adsorption surface in various salt concentrations. These results provide useful insights into bioseparation, soil remediation, controlled release by the applications of triblock co-polymers.
Keywords:triblock copolymer;methacrylic polyampholytes;isothermal titration calorimetry;critical micelle concentration;hydrophobicity;adsorption