| Autor: |
Deng X; Department of Chemical and Biomolecular Engineering , Vanderbilt University , Nashville , Tennessee , 37205., Livingston JL; Department of Chemical and Biomolecular Engineering , Vanderbilt University , Nashville , Tennessee , 37205., Spear NJ; Department of Chemical and Biomolecular Engineering , Vanderbilt University , Nashville , Tennessee , 37205., Jennings GK; Department of Chemical and Biomolecular Engineering , Vanderbilt University , Nashville , Tennessee , 37205. |
| Abstrakt: |
We report the preparation of pH-responsive, ester/carboxylic acid random copolymer films via simple modification of poly(norbornene diacyl chloride) (pNBDAC), prepared via surface-initiated ring-opening metathesis polymerization, with mixtures of water and ethanol to form carboxylic acid and ethyl ester side groups. The pNBDAC film serves as a compositionally versatile platform to controllably obtain copolymers with multiple functionalities. In modifying the pNBDAC to form the copolymer film, ethanol exhibits a significantly higher reactivity with acyl chloride groups within the film than does water. The magnitude and range of the pH-responsive performance are highly dependent on the carboxylic acid content in the copolymer films, which demonstrates the effect of film hydrophilicity on the pH-responsive switching of ionic barrier properties. The resistance of the film against ion transfer can be decreased by a factor of 10 4 through pH change, demonstrating pH-induced switching from hydrophobic and insulating to swollen and ion-permeable films. The interactions of the copolymer films with water at different pH values were also explored. When the copolymer contains 34% carboxylic acids, a 4× greater film thickness is obtained in high pH solution than in low pH solution due to ionically driven water swelling. The reversibility of the pH-responsive performance of these copolymer films is high based on measurements using quartz crystal microbalance with dissipation (QCM-D). |
