The Effect of Hydrostatic Pressure on the Lower Critical Ordering Transition in Diblock Copolymers
| Autor: | MA Pollard, Yves Gallot, Anne M. Mayes, Thomas P. Russell, A. V. Ruzette |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
chemistry.chemical_classification
Materials science Polymers and Plastics Organic Chemistry Hydrostatic pressure Thermodynamics Polymer Lower critical solution temperature Small-angle neutron scattering Inorganic Chemistry chemistry.chemical_compound chemistry Volume (thermodynamics) Polymer chemistry Materials Chemistry Copolymer Polystyrene Order of magnitude |
| Zdroj: | Macromolecules. 31:6493-6498 |
| ISSN: | 1520-5835 0024-9297 |
| Popis: | The effect of hydrostatic pressure on the lower critical ordering transition (LCOT) was investigated by in situ small angle neutron scattering on symmetric and asymmetric diblock copolymers of perdeuterated polystyrene and poly(n-butyl methacrylate). These systems exhibit a transition from the disordered to ordered state upon heating. Similar to the lower critical solution transition (LCST) in polymer mixtures, the LCOT is entropically driven and is accompanied by an increase in volume on demixing of the copolymer blocks. As a consequence, application of hydrostatic pressure markedly increases the temperature at which the transition from the disordered to the ordered state occurs. Small angle neutron scattering studies as a function of temperature and pressure show that the pressure dependence of the LCOT, ΔTLCOT/ΔP, is up to +147 °C/kbar (1.45 ± 0.07 °C/MPa), roughly 1 order of magnitude greater than that seen at elevated pressures for diblock copolymers exhibiting an upper critical ordering transition (... |
| Databáze: | OpenAIRE |
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