Phase-Separation Dynamics of Aqueous Poly (N-isopropylacrylamide) Solutions: Characteristic Behavior of the Molecular Weight and Concentration Dependences
| Autor: | Noboru Kitamura, Tatsuya Shoji, Yasuyuki Tsuboi, Takanori Tada |
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| Rok vydání: | 2012 |
| Předmět: |
High concentration
Aqueous solution Materials science Polymers and Plastics Organic Chemistry Kinetics Time constant Analytical chemistry Condensed Matter Physics Laser law.invention Photometry (optics) Behavioral traits chemistry.chemical_compound chemistry law Polymer chemistry Materials Chemistry Poly(N-isopropylacrylamide) Physical and Theoretical Chemistry |
| Zdroj: | Macromolecular Chemistry and Physics. 213:1879-1884 |
| ISSN: | 1022-1352 |
| Popis: | The dynamics of thermoresponsive phase-separation processes in aqueous poly(N-isopropylacrylamide) (PNIPAM) was studied using a laser temperature-jump technique combined with photometry. The time constant for phase separation (τ) was determined with high accuracy for various molecular weights (Mw) and concentrations (C) of PNIPAM in solution. For the C-dependence, τ decreased with increasing concentration, and eventually converged to a constant value (≈ 50 ms) at high concentration. Such behavior can be interpreted in terms of inter-polymer-chain entanglement and diffusion prior to phase separation. On the other hand, there was an optimum value of Mw at which the phase separation was fastest. The origins of these experimental results are discussed within the framework of a diffusion-controlled model. |
| Databáze: | OpenAIRE |
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