ORIGINAL CONTRIBUTION Novel thermoresponsive block copolymers having different architectures—structural, rheological, thermal, and dielectric investigations Konstantinos Kyriakos & Dionysia Aravopoulou & Lukas Augsbach & Josef Sapper & Sarah Ottinger & Christina Psylla & Ali Aghebat Rafat & Carlos Adrian Benitez-Montoya & Anna Miasnikova & Zhenyu Di & André Laschewsky & Peter Müller-Buschbaum & Apostolos Kyritsis & Christine M. Papadakis Received: 28 March 2014 /Revised: 20 May 2014 /Accepted: 20 May 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract Thermoresponsive block copolymers comprising long, hydrophilic, nonionic poly(methoxy diethylene glycol acrylate) (PMDEGA) blocks and short hydrophobic polysty- rene (PS) blocks are investigated in aqueous solution. Various architectures, namely diblock, triblock, and starblock copoly- mers are studied as well as a PMDEGA homopolymer as reference, over a wide concentration range. For specific char- acterization methods, polymers were labeled, either by partial deuteration (for neutron scattering studies) or by fluorophores. Using fluorescence correlation spectroscopy, critical micelli- zation concentrations are identified and the hydrodynamic radii of the micelles, r h mic , are determined. Using dynamic light scattering, the behavior of r h mic in dependence on temperature and the cloud points are measured. Small-angle neutron scat- tering enabled the detailed structural investigation of the mi- celles and their aggregates below and above the cloud point. Viscosity measurements are carried out to determine the acti- vation energies in dependence on the molecular architecture. Differential scanning calorimetry at high polymer concentra- tion 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. Keywords Block copolymers . Thermoresponsive . Structural investigations . Mechanical properties . Thermal behavior . Dielectric properties Introduction Typically, nonionic thermoresponsive polymers in aqueous solution display lower critical solution temperature (LCST) behavior, i.e., they are water-soluble and swollen below the cloud point (CP) but water-insoluble and collapsed above [1, 2]. The collapsed polymers often form large aggregates of stable size, the so-called mesoglobules [3, 4]. Most studies have so far addressed poly(N-isopropyl acrylamide), PNIPAM [5], providing a wealth of findings, from the molecular inter- action with water [6–8] over the chain collapse [9] to the aggregate formation [3, 4, 10, 11]. We have recently synthesized and investigated a new type of thermoresponsive polymers, namely, poly(methoxy K. Kyriakos : L. Augsbach : J. Sapper : S. Ottinger : C. Psylla : A. Aghebat Rafat : P. Müller-Buschbaum : C. M. Papadakis (*) Physik-Department, Fachgebiet Physik weicher Materie/Lehrstuhl Physik funktioneller Materialien, Technische Universität München, James-Franck-Str. 1, 85748 Garching, Germany e-mail: papadakis@tum.de D. Aravopoulou : A. Kyritsis Physics Department, National Technical University of Athens, Iroon Polytechneiou 9, Zografou Campus, Athens 15780, Greece C. A. Benitez-Montoya : A. Miasnikova : A. Laschewsky Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany Z. Di Jülich Centre for Neutron Science (JCNS), Forschungszentrum Jülich GmbH, Outstation at MLZ, Lichtenbergstr. 1, 85748 Garching, Germany A. Laschewsky Fraunhofer Institut für Angewandte Polymerforschung, Geiselbergstr. 69, 14476 Potsdam-Golm, Germany Colloid Polym Sci DOI 10.1007/s00396-014-3282-0