| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 5178916 | Polymer | 2016 | 9 Pages |
•Polymethacrylamide homopolymers based on tertiary amine-modified l-alanine are prepared.•The incorporated natural amino acid moiety endow polymers with optical activity.•Monomer structure is critical for polymer to exhibit desired responsive property.•Polymers display LCST in basic pH range and effects of various factors are studied.•Copolymerization is not necessary to obtain multi-responsive polymers.
Four poly(N-methacryloyl-l-alanine) homopolymers containing different tertiary amine moieties, dimethylaminoethyl, dimethylaminopropyl, diethylaminoethyl, and diethylaminopropyl, were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization in an effort to use natural amino acids as building blocks to design stimuli-responsive polymers that display pH-tunable lower critical solution temperature (LCST) transitions in the basic pH range. Monomer structure was found to be critical for the corresponding polymer to exhibit desired stimuli-responsive properties in water. While all four polymethacrylamides showed thermosensitive property in water, only poly(N-methacryloyl-l-alanine 2-(diethylamino)ethylamide) (PMAEE) exhibited LCST behavior in a wide pH range, from 9.0 to 13.0. Other polymers' thermoresponsive properties were found either at very high pH values (e.g., ≥13.0) or in a rather narrow pH range. The effects of pH, polymer molecular weight, polymer concentration, presence of NaCl, and end groups on cloud point of PMAEE in water were investigated; the cloud point decreased with the increase of solution pH and polymer concentration, the addition of NaCl, and the introduction of a more hydrophobic end group but varied little with polymer molecular weight. The incorporation of tertiary amine moieties endowed the polymers with a CO2-responsive property; we demonstrated that the thermosensitive property of PMAEE can be reversibly tuned by bubbling its solution alternately with CO2 and N2 gases.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (212 K)Download as PowerPoint slide
