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 - Philipp, Martine A1 - Adelsberger, Joseph A1 - Jaksch, Sebastian A1 - Berezkin, Anatoly V. A1 - Lugo, Dersy M. A1 - Richtering, Walter A1 - Grillo, Isabelle A1 - Miasnikova, Anna A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Cononsolvency of water/methanol mixtures for PNIPAM and PS-b-PNIPAM: pathway of aggregate formation investigated using time-resolved SANS JF - Macromolecules : a publication of the American Chemical Society N2 - We investigate the cononsolvency effect of poly(N-isopropylacrylamide) (PNIPAM) in mixtures of water and methanol. Two systems are studied: micellar solutions of polystyrene-b-poly(N-isopropylacrylamide) (PS-b-PNIPAM) diblock copolymers and, as a reference, solutions of PNIPAM homopolymers, both at a concentration of 20 mg/mL in DO. Using a stopped-flow instrument, fully deuterated methanol was rapidly added to these solutions at volume fractions between 10 and 20%. Time-resolved turbidimetry revealed aggregate formation within 10-100 s. The structural changes on mesoscopic length scales were followed by time-resolved small-angle neutron scattering (TR-SANS) with a time resolution of 0.1 s. In both systems, the pathway of the aggregation depends on the content of deuterated methanol; however, it is fundamentally different for homopolymer and diblock copolymer solutions: In the former, very large aggregates (>150 nm) are formed within the dead time of the setup, gradient appears at their surface in the late stages. In contrast, the growth of the aggregates in the latter system features different regimes, and the final aggregate size is 50 nm, thus much smaller than for the homopolymer. For the diblock copolymer, the time dependence of the aggregate radius can be described by two models: In the initial stage, the diffusion-limited coalescence model describes the data well; however, the resulting coalescence time is unreasonably high. In the late stage, a logarithmic coalescence model based on an energy barrier which is proportional to the aggregate radius is successfully applied. and a concentration Y1 - 2014 U6 - https://doi.org/10.1021/ma501434e SN - 0024-9297 SN - 1520-5835 VL - 47 IS - 19 SP - 6867 EP - 6879 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Meier-Koll, Andreas A1 - Bivigou Koumba, Achille Mayelle A1 - Busch, Peter A1 - Holderer, Olaf A1 - Hellweg, Thomas A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - The collapse transition and the segmental dynamics in concentrated micellar solutions of P(S-b-NIPAM) diblock copolymers JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - We investigate concentrated solutions of poly(styrene-b-N-isopropyl acrylamide) (P(S-b-NIPAM)) diblock copolymers in deuterated water (D2O). Both structural changes and the changes of the segmental dynamics occurring upon heating through the lower critical solution temperature (LCST) of PNIPAM are studied using small-angle neutron scattering and neutron spin-echo spectroscopy. The collapse of the micellar shell and the cluster formation of collapsed micelles at the LCST as well as an increase of the segmental diffusion coefficient after crossing the LCST are detected. Comparing to our recent results on a triblock copolymer P(S-b-NIPAM-b-S) [25], we observe that the collapse transition of P(S-b-NIPAM) is more complex and that the PNIPAM segmental dynamics are faster than in P(S-b-NIPAM-b-S). KW - Block copolymers KW - Responsive polymers KW - Small-angle neutron scattering KW - Neutron spin-echo spectroscopy Y1 - 2011 U6 - https://doi.org/10.1007/s00396-011-2382-3 SN - 0303-402X VL - 289 IS - 5-6 SP - 711 EP - 720 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 - TY - JOUR A1 - Adelsberger, Joseph A1 - Metwalli, Ezzeldin A1 - Diethert, Alexander A1 - Grillo, Isabelle A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Kinetics of collapse transition and cluster formation in a thermoresponsive micellar solution of P(S-b-NIPAM-b-S) induced by a temperature jump JF - Macromolecular rapid communications N2 - Structural changes at the intra- as well as intermicellar level were induced by the LCST-type collapse transition of poly(N-isopropyl acrylamide) in ABA triblock copolymer micelles in water. The distinct process kinetics was followed in situ and in real-time using time-resolved small-angle neutron scattering (SANS), while a micellar solution of a triblock copolymer, consisting of two short deuterated polystyrene endblocks and a long thermoresponsive poly(N-isopropyl acrylamide) middle block, was heated rapidly above its cloud point. A very fast collapse together with a multistep aggregation behavior is observed. The findings of the transition occurring at several size and time levels may have implications for the design and application of such thermoresponsive self-assembled systems. KW - polymer physics KW - thermoresponsive polymers KW - small-angle neutron scattering KW - time-resolved measurements Y1 - 2012 U6 - https://doi.org/10.1002/marc.201100631 SN - 1022-1336 VL - 33 IS - 3 SP - 254 EP - 259 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Grillo, Isabelle A1 - Kulkarni, Amit A1 - Sharp, Melissa A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Kinetics of aggregation in micellar solutions of thermoresponsive triblock copolymers - influence of concentration, start and target temperatures JF - Soft matter N2 - In aqueous solution, symmetric triblock copolymers with a thermoresponsive middle block and hydrophobic end blocks form flower-like core-shell micelles which collapse and aggregate upon heating through the cloud point (CP). The collapse of the micellar shell and the intermicellar aggregation are followed in situ and in real-time using time-resolved small-angle neutron scattering (SANS), while heating micellar solutions of a poly((styrene-d(8))-b-(N-isopropyl acrylamide)-b-(styrene-d(8))) triblock copolymer in D2O rapidly through their CP. The influence of polymer concentration as well as of the start and target temperatures is addressed. In all cases, the micellar collapse is very fast. The collapsed micelles immediately form small clusters which contain voids. They densify which slows down or even stops their growth. For low concentrations and target temperatures just above the CP, i.e. shallow temperature jumps, the subsequent growth of the clusters is described by diffusion-limited aggregation. In contrast, for higher concentrations and/or higher target temperatures, i.e. deep temperature jumps, intermicellar bridges dominate the growth. Eventually, in all cases, the clusters coagulate which results in macroscopic phase separation. For shallow temperature jumps, the cluster surfaces stay rough; whereas for deep temperature jumps, a concentration gradient develops at late stages. These results are important for the development of conditions for thermal switching in applications, e.g. for the use of thermoresponsive micellar systems for transport and delivery purposes. Y1 - 2013 U6 - https://doi.org/10.1039/c2sm27152d SN - 1744-683X VL - 9 IS - 5 SP - 1685 EP - 1699 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Zhong, Qi A1 - Adelsberger, Joseph A1 - Niedermeier, M. A. A1 - Golosova, Anastasi A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Funari, S. S. A1 - Papadakis, Christine M. A1 - Müller-Buschbaum, Peter T1 - The influence of selective solvents on the transition behavior of poly(styrene-b-monomethoxydiethylenglycol-acrylate-b-styrene) thick films JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - Thick poly(styrene-b-monomethoxydiethylenglycol-acrylate-b-styrene) [P(S-b-MDEGA-b-S)] films (thickness 5 mu m) are prepared from different solvents on flexible substrates by solution casting and investigated with small-angle X-ray scattering. As the solvents are either PS- or PMDEGA-selective, micelles with different core-shell micellar structures are formed. In PMDEGA-selective solvents, the PS block is the core and PMDEGA is the shell, whereas in PS-selective solvents, the order is reversed. After exposing the films to liquid D2O, the micellar structure inside the films prepared from PMDEGA-selective solvents remains unchanged and only the PMDEGA (shell part) swells. On the contrary, in the films prepared from PS-selective solvents, the micelles revert the core and the shell. This reversal causes more entanglements of the PMDEGA chains between the micelles. Moreover, the thermal collapse transition of the PMDEGA block in liquid D2O is significantly broadened. Irrespective of the solvent used for film preparation, the swollen PMDEGA shell does not show a prominent shrinkage when passing the phase transition, and the transition process occurs via compaction. The collapsed micelles have a tendency to densely pack above the transition temperature. KW - Hydrogel KW - Thin film KW - Thermo-responsive KW - LCST behavior KW - SAXS Y1 - 2013 U6 - https://doi.org/10.1007/s00396-012-2879-4 SN - 0303-402X VL - 291 IS - 6 SP - 1439 EP - 1451 PB - Springer CY - New York ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Kulkarni, Amit A1 - Jain, Abhinav A1 - Wang, Weinan A1 - Bivigou Koumba, Achille Mayelle A1 - Busch, Peter A1 - Pipich, Vitaliy A1 - Holderer, Olaf A1 - Hellweg, Thomas A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Thermoresponsive PS-b-PNIPAM-b-PS micelles : aggregation behavior, segmental dynamics, and thermal response N2 - We have studied I lie thermal behavior of amphiphilic, symmetric triblock copolymers having short, deuterated polystyrene (PS) end blocks and a large poly(N-isopropylacrylarnicle) (PNIPAM) middle block exhibiting a lower critical solution temperature (LCST) in aqueous solution. A wide range of concentrations (0.1-300 mg/mL) is investigated using it number of analytical methods such as fluorescence correlation spectroscopy (FCS), turbidimetry, dynamic light scattering (DLS), small-angle neutron scattering (SANS), and neutron spin-echo spectroscopy (NSE). The critical micelle concentration is determined using FCS to be 1 mu M or less. The collapse of the micelles at the LCST is investigated using turbidimetry and DLS and shows a weak dependence on the degree of polymerization of the PNIPAM block. SANS with contrast matching allows its to reveal the core-shell Structure of the micelles as well as their correlation as a function of temperature. The segmental dynamics of the PNIPAM shell are studied as a function of temperature and arc found to be faster in the collapsed state than in the swollen state. The mode detected has a linear dispersion in q(2) and is found to be faster in the collapsed state as compared to the swollen state. We attribute this result to the averaging over mobile and immobilized segments. Y1 - 2010 UR - http://pubs.acs.org/journal/mamobx U6 - https://doi.org/10.1021/Ma902714p SN - 0024-9297 ER -