TY - JOUR A1 - Bogomolova, Anna A1 - Secker, Christian A1 - Koetz, Joachim A1 - Schlaad, Helmut T1 - Thermo-induced multistep assembly of double-hydrophilic block copolypeptoids in water JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - The aqueous solution behavior of thermoresponsive-hydrophilic block copolypeptoids, i.e., poly(N-(n-propyl)glycine) (x) -block-poly(N-methylglycine) (y) (x = 70; y = 23, 42, 76), in the temperature range of 20-45 A degrees C is studied. Turbidimetric analyses of the 0.1 wt% aqueous solutions reveal two cloud points at T (cp)similar to 30 and 45 A degrees C and a clearing point in between at T (cl)similar to 42 A degrees C. Temperature-dependent dynamic light scattering (DLS) suggest that right above the first collapse temperature, single polymer molecules assemble into large structures which upon further heating, i.e., at the clearing point temperature, disassemble into micelle-like structures. Upon further heating, the aggregates start to grow again in size, as recognized by the second cloud point, through a crystallization process. KW - Polypeptoids KW - Block copolymers KW - Thermoresponsive KW - Self-assembly Y1 - 2017 U6 - https://doi.org/10.1007/s00396-017-4044-6 SN - 0303-402X SN - 1435-1536 VL - 295 SP - 1305 EP - 1312 PB - Springer CY - New York ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Bivigou Koumba, Achille Mayelle A1 - Miasnikova, Anna A1 - Busch, Peter A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Polystyrene-block-poly (methoxy diethylene glycol acrylate)-block-polystyrene triblock copolymers in aqueous solution-a SANS study of the temperature-induced switching behavior JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - A concentrated solution of a symmetric triblock copolymer with a thermoresponsive poly(methoxy diethylene glycol acrylate) (PMDEGA) middle block and short hydrophobic, fully deuterated polystyrene end blocks is investigated in D2O where it undergoes a lower critical solution temperature-type phase transition at ca. 36 A degrees C. Small-angle neutron scattering (SANS) in a wide temperature range (15-50 A degrees C) is used to characterize the size and inner structure of the micelles as well as the correlation between the micelles and the formation of aggregates by the micelles above the cloud point (CP). A model featuring spherical core-shell micelles, which are correlated by a hard-sphere potential or a sticky hard-sphere potential together with a Guinier form factor describing aggregates formed by the micelles above the CP, fits the SANS curves well in the entire temperature range. The thickness of the thermoresponsive micellar PMDEGA shell as well as the hard-sphere radius increase slightly already below the cloud point. Whereas the thickness of the thermoresponsive micellar shell hardly shrinks when heating through the CP and up to 50 A degrees C, the hard-sphere radius decreases within 3.5 K at the CP. The volume fraction decreases already significantly below the CP, which may be at the origin of the previously observed gel-sol transition far below the CP (Miasnikova et al., Langmuir 28: 4479-4490, 2012). Above the CP, small, and at higher temperatures, large aggregates are formed by the micelles. KW - Hydrogel KW - Thermoresponsive KW - LCST behavior KW - SANS Y1 - 2015 U6 - https://doi.org/10.1007/s00396-015-3535-6 SN - 0303-402X SN - 1435-1536 VL - 293 IS - 5 SP - 1515 EP - 1523 PB - Springer CY - New York ER - TY - JOUR A1 - Kyriakos, Konstantinos A1 - Aravopoulou, Dionysia A1 - Augsbach, Lukas A1 - Sapper, Josef A1 - Ottinger, Sarah A1 - Psylla, Christina A1 - Rafat, Ali Aghebat A1 - Benitez-Montoya, Carlos Adrian A1 - Miasnikova, Anna A1 - Di, Zhenyu A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Kyritsis, Apostolos A1 - Papadakis, Christine M. T1 - Novel thermoresponsive block copolymers having different architectures-structural, rheological, thermal, and dielectric investigations JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - 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 (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 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. KW - Block copolymers KW - Thermoresponsive KW - Structural investigations KW - Mechanical properties KW - Thermal behavior KW - Dielectric properties Y1 - 2014 U6 - https://doi.org/10.1007/s00396-014-3282-0 SN - 0303-402X SN - 1435-1536 VL - 292 IS - 8 SP - 1757 EP - 1774 PB - Springer CY - New York ER - TY - JOUR A1 - Zhong, Qi A1 - Wang, Weinan A1 - Adelsberger, Joseph A1 - Golosova, Anastasia A1 - Koumba, Achille M. Bivigou A1 - Laschewsky, André A1 - Funari, Sergio S. A1 - Perlich, Jan A1 - Roth, Stephan V. A1 - Papadakis, Christine M. A1 - Müller-Buschbaum, Peter T1 - Collapse transition in thin films of poly(methoxydiethylenglycol acrylate) JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - The thermal behavior of poly(methoxydiethylenglycol acrylate) (PMDEGA) is studied in thin hydrogel films on solid supports and is compared with the behavior in aqueous solution. The PMDEGA hydrogel film thickness is varied from 2 to 422 nm. Initially, these films are homogenous, as measured with optical microscopy, atomic force microscopy, X-ray reflectivity, and grazing-incidence small-angle X-ray scattering (GISAXS). However, they tend to de-wet when stored under ambient conditions. Along the surface normal, no long-ranged correlations between substrate and film surface are detected with GISAXS, due to the high mobility of the polymer at room temperature. The swelling of the hydrogel films as a function of the water vapor pressure and the temperature are probed for saturated water vapor pressures between 2,380 and 3,170 Pa. While the swelling capability is found to increase with water vapor pressure, swelling in dependence on the temperature revealed a collapse phase transition of a lower critical solution temperature type. The transition temperature decreases from 40.6 A degrees C to 36.6 A degrees C with increasing film thickness, but is independent of the thickness for very thin films below a thickness of 40 nm. The observed transition temperature range compares well with the cloud points observed in dilute (0.1 wt.%) and semi-dilute (5 wt.%) solution which decrease from 45 A degrees C to 39 A degrees C with increasing concentration. KW - Hydrogel KW - Thin film KW - Thermoresponsive KW - LCST behavior KW - GISAXS KW - AFM Y1 - 2011 U6 - https://doi.org/10.1007/s00396-011-2384-1 SN - 0303-402X VL - 289 IS - 5-6 SP - 569 EP - 581 PB - Springer CY - New York ER -