Novel thermoresponsive block copolymers having different architectures—structural, rheological, thermal, and dielectric investigations
| Autor: | Peter Müller-Buschbaum, Anna Miasnikova, Zhenyu Di, Christina Psylla, Christine M. Papadakis, Lukas Augsbach, Konstantinos Kyriakos, Sarah Ottinger, Ali Aghebat Rafat, André Laschewsky, Apostolos Kyritsis, Josef Sapper, Dionysia Aravopoulou, Carlos Adrian Benitez-Montoya |
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| Rok vydání: | 2014 |
| Předmět: |
chemistry.chemical_classification
Phase transition Materials science Polymers and Plastics Polymer Neutron scattering Micelle chemistry.chemical_compound Colloid and Surface Chemistry Differential scanning calorimetry chemistry Dynamic light scattering Chemical engineering Polymer chemistry Materials Chemistry Institut für Chemie Polystyrene Physical and Theoretical Chemistry Glass transition |
| Zdroj: | Colloid and Polymer Science. 292:1757-1774 |
| ISSN: | 1435-1536 0303-402X |
| DOI: | 10.1007/s00396-014-3282-0 |
| Popis: | Thermoresponsive block copolymers comprising long, hydrophilic, nonionic poly(methoxy diethylene glycol acrylate) (PMDEGA) blocks and short hydrophobic polystyrene (PS) blocks are investigated in aqueous solution. Various architectures, namely diblock, triblock, and starblock copolymers are studied as well as a PMDEGA homopolymer as reference, over a wide concentration range. For specific characterization methods, polymers were labeled, either by partial deuteration (for neutron scattering studies) or by fluorophores. Using fluorescence correlation spectroscopy, critical micellization concentrations are identified and the hydrodynamic radii of the micelles, r , are determined. Using dynamic light scattering, the behavior of r in dependence on temperature and the cloud points are measured. Small-angle neutron scattering enabled the detailed structural investigation of the micelles and their aggregates below and above the cloud point. Viscosity measurements are carried out to determine the activation energies in dependence on the molecular architecture. Differential scanning calorimetry at high polymer concentration reveals the glass transition of the polymers, the fraction of uncrystallized water and effects of the phase transition at the cloud point. Dielectric relaxation spectroscopy shows that the polarization changes reversibly at the cloud point, which reflects the formation of large aggregates upon heating through the cloud point and their redissolution upon cooling. |
| Databáze: | OpenAIRE |
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