TY - JOUR A1 - Zhong, Qi A1 - Metwalli, Ezzeldin A1 - Rawolle, Monika A1 - Kaune, Gunar A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Papadakis, Christine M. A1 - Cubitt, Robert A1 - Müller-Buschbaum, Peter T1 - Rehydration of Thermoresponsive Poly(monomethoxydiethylene glycol acrylate) Films Probed in Situ by Real-Time Neutron Reflectivity JF - Macromolecules : a publication of the American Chemical Society N2 - The rehydration of thermoresponsive poly(monomethoxydiethylene glycol acrylate) (PMDEGA) films exhibiting a lower critical solution temperature (LCST) type demixing phase transition in aqueous environments, induced by a decrease in temperature, is investigated in situ with real-time neutron reflectivity. Two different starting conditions (collapsed versus partially swollen chain conformation) are compared. In one experiment, the temperature is reduced from above the demixing temperature to well below the demixing temperature. In a second experiment, the starting temperature is below the demixing temperature, but within the transition regime, and reduced to the same final temperature. In both cases, the observed rehydration process can be divided into three stages: first condensation of water from the surrounding atmosphere, then absorption of water by the PMDEGA film and evaporation of excess water, and finally, rearrangement of the PMDEGA chains. The final rehydrated film is thicker and contains more absorbed water as compared with the initially swollen film at the same temperature well below the demixing temperature. Y1 - 2015 U6 - https://doi.org/10.1021/acs.macromol.5b00645 SN - 0024-9297 SN - 1520-5835 VL - 48 IS - 11 SP - 3604 EP - 3612 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 - 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 - GEN A1 - Troll, K. A1 - Kulkarni, Amit A1 - Wang, W. A1 - Darko, C. A1 - Koumba, A. M. Bivigou A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - The collapse transition of poly(styrene-b-(N-isopropyl acrylamide)) diblock copolymers in aqueous solution and in thin films T2 - Colloid and polymer science : official journal of the Kolloid-Gesellschaft Y1 - 2011 U6 - https://doi.org/10.1007/s00396-010-2344-1 SN - 0303-402X VL - 289 IS - 2 SP - 227 EP - 227 PB - Springer CY - New York ER - TY - JOUR A1 - Vishnevetskaya, Natalya S. A1 - Hildebrand, Viet A1 - Niebuur, Bart-Jan A1 - Grillo, Isabelle A1 - Filippov, Sergey K. A1 - Laschewsky, Andre A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Aggregation Behavior of Doubly Thermoresponsive Polysulfobetaine-b-poly(N-isopropylacrylamide) Diblock Copolymers JF - Macromolecules : a publication of the American Chemical Society N2 - A 2-fold thermoresponsive diblock copolymer PSPP430-b-PNIPAM(200) consisting of a zwitterionic polysulfobetaine (PSPP) block and a nonionic poly(N-isopropylacrylamide) (PNIPAM) block is prepared by successive RAFT polymerizations. In aqueous solution, the corresponding homopolymers PSPP and PNIPAM feature both upper and lower critical solution temperature (UCST and LCST) behavior, respectively. The diblock copolymer exhibits thermally induced "schizophrenic" aggregation behavior in aqueous solutions. Moreover, the ion sensitivity of the, cloud point of the zwitterionic PSPP block to both the ionic strength and the nature of the salt offers the possibility to create switchable systems which respond sensitively to changes of the temperature and of the electrolyte type and concentration. The diblock copolymer solutions in D2O are investigated by means of turbidimetry and small-angle neutron scattering (SANS) with respect to the phase behavior and the self-assembled structures in dependence on temperature and electrolyte content. Marked, differences of the aggregation below the UCST-type and above the LCST-type transition are observed. The addition of a small amount of NaBr (0.004 M) does not affect the overall behavior, and only the UCST-type transition and aggregate structures are slightly altered, reflecting the well-known ion sensitivity of the zwitterionic PSPP block. Y1 - 2016 U6 - https://doi.org/10.1021/acs.macromol.6b01186 SN - 0024-9297 SN - 1520-5835 VL - 49 SP - 6655 EP - 6668 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Hu, Neng A1 - Lin, Li A1 - Metwalli, Ezzeldin A1 - Bießmann, Lorenz A1 - Philipp, Martine A1 - Hildebrand, Viet A1 - Laschewsky, André A1 - Papadakis, Christine M. A1 - Cubitt, Robert A1 - Zhong, Qi A1 - Müller-Buschbaum, Peter T1 - Kinetics of water transfer between the LCST and UCST thermoresponsive blocks in diblock copolymer thin films monitored by in situ neutron reflectivity JF - Advanced materials interfaces N2 - The kinetics of water transfer between the lower critical solution temperature (LCST) and upper critical solution temperature (UCST) thermoresponsive blocks in about 10 nm thin films of a diblock copolymer is monitored by in situ neutron reflectivity. The UCST-exhibiting block in the copolymer consists of the zwitterionic poly(4((3-methacrylamidopropyl)dimethylammonio)butane-1-sulfonate), abbreviated as PSBP. The LCST-exhibiting block consists of the nonionic poly(N-isopropylacrylamide), abbreviated as PNIPAM. The as-prepared PSBP80-b-PNIPAM(400) films feature a three-layer structure, i.e., PNIPAM, mixed PNIPAM and PSBP, and PSBP. Both blocks have similar transition temperatures (TTs), namely around 32 degrees C for PNIPAM, and around 35 degrees C for PSBP, and with a two-step heating protocol (20 degrees C to 40 degrees C and 40 degrees C to 80 degrees C), both TTs are passed. The response to such a thermal stimulus turns out to be complex. Besides a three-step process (shrinkage, rearrangement, and reswelling), a continuous transfer of D2O from the PNIPAM to the PSBP block is observed. Due to the existence of both, LCST and UCST blocks in the PSBP80-b-PNIPAM(400 )film, the water transfer from the contracting PNIPAM, and mixed layers to the expanding PSBP layer occurs. Thus, the hydration kinetics and thermal response differ markedly from a thermoresponsive polymer film with a single LCST transition. KW - block copolymer KW - dual thermoresponsive KW - kinetic water transfer KW - neutron KW - reflectivity KW - thin film Y1 - 2022 U6 - https://doi.org/10.1002/admi.202201913 SN - 2196-7350 VL - 10 IS - 3 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Hildebrand, Viet A1 - Laschewsky, Andre A1 - Päch, Michael A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Effect of the zwitterion structure on the thermo-responsive behaviour of poly(sulfobetaine methacrylates) JF - Polymer Chemistry N2 - A series of new sulfobetaine methacrylates, including nitrogen-containing saturated heterocycles, was synthesised by systematically varying the substituents of the zwitterionic group. Radical polymerisation via the RAFT (reversible addition–fragmentation chain transfer) method in trifluoroethanol proceeded smoothly and was well controlled, yielding polymers with predictable molar masses. Molar mass analysis and control of the end-group fidelity were facilitated by end-group labeling with a fluorescent dye. The polymers showed distinct thermo-responsive behaviour of the UCST (upper critical solution temperature) type in an aqueous solution, which could not be simply correlated to their molecular structure via an incremental analysis of the hydrophilic and hydrophobic elements incorporated within them. Increasing the spacer length separating the ammonium and the sulfonate groups of the zwitterion moiety from three to four carbons increased the phase transition temperatures markedly, whereas increasing the length of the spacer separating the ammonium group and the carboxylate ester group on the backbone from two to three carbons provoked the opposite effect. Moreover, the phase transition temperatures of the analogous polyzwitterions decreased in the order dimethylammonio > morpholinio > piperidinio alkanesulfonates. In addition to the basic effect of the polymers’ precise molecular structure, the concentration and the molar mass dependence of the phase transition temperatures were studied. Furthermore, we investigated the influence of added low molar mass salts on the aqueous-phase behaviour for sodium chloride and sodium bromide as well as sodium and ammonium sulfate. The strong effects evolved in a complex way with the salt concentration. The strength of these effects depended on the nature of the anion added, increasing in the order sulfate < chloride < bromide, thus following the empirical Hofmeister series. In contrast, no significant differences were observed when changing the cation, i.e. when adding sodium or ammonium sulfate. Y1 - 2016 U6 - https://doi.org/10.1039/c6py01220e SN - 1759-9954 SN - 1759-9962 VL - 8 SP - 310 EP - 322 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Zhong, Qi A1 - Metwalli, Ezzeldin A1 - Rawolle, Monika A1 - Kaune, Gunar A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Papadakis, Christine M. A1 - Cubitt, Robert A1 - Müller-Buschbaum, Peter T1 - Structure and Thermal Response of Thin Thermoresponsive Polystyrene-block-poly(methoxydiethylene glycol acrylate)-block-polystyrene Films JF - Macromolecules : a publication of the American Chemical Society N2 - Thin thermoresponsive films of the triblock copolymer polystyrene-block-poly(methoxydiethylene glycol acrylate)-block-polystyrene (P(S-b-MDEGA-b-S)) are investigated on silicon substrates. By spin coating, homogeneous and smooth films are prepared for a range of film thicknesses from 6 to 82 nm. Films are stable with respect to dewetting as investigated with optical microscopy and atomic force microscopy. P(S-b-MDEGA-b-S) films with a thickness of 39 nm exhibit a phase transition of the lower critical solution temperature (LCST) type at 36.5 degrees C. The swelling and the thermoresponsive behavior of the films with respect to a sudden thermal stimulus are probed with in-situ neutron reflectivity. In undersaturated water vapor swelling proceeds without thickness increase. The thermoresponse proceeds in three steps: First, the film rejects water as the temperature is above LCST. Next, it stays constant for 600 s, before the collapsed film takes up water again. With ATR-FTIR measurements, changes of bound water in the film caused by different thermal stimuli are studied. Hydrogen bonds only form between C=O and water in the swollen film. Above the LCST most hydrogen bonds with water are broken, but some amount of bound water remains inside the film in agreement with the neutron reflectivity data. Grazing-incidence small-angle X-ray scattering (GISAXS) shows that the inner lateral structure is not significantly influenced by the different thermal stimuli. Y1 - 2013 U6 - https://doi.org/10.1021/ma400627u SN - 0024-9297 VL - 46 IS - 10 SP - 4069 EP - 4080 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Reitenbach, Julija A1 - Geiger, Christina A1 - Wang, Peixi A1 - Vagias, Apostolos N. A1 - Cubitt, Robert A1 - Schanzenbach, Dirk A1 - Laschewsky, André A1 - Papadakis, Christine M. A1 - Müller-Buschbaum, Peter T1 - Effect of magnesium salts with chaotropic anions on the swelling behavior of PNIPMAM thin films JF - Macromolecules : a publication of the American Chemical Society N2 - Poly(N-isopropylmethacrylamide) (PNIPMAM) is a stimuli responsive polymer, which in thin film geometry exhibits a volume-phase transition upon temperature increase in water vapor. The swelling behavior of PNIPMAM thin films containing magnesium salts in water vapor is investigated in view of their potential application as nanodevices. Both the extent and the kinetics of the swelling ratio as well as the water content are probed with in situ time-of-flight neutron reflectometry. Additionally, in situ Fourier-transform infrared (FTIR) spectroscopy provides information about the local solvation of the specific functional groups, while two-dimensional FTIR correlation analysis further elucidates the temporal sequence of solvation events. The addition of Mg(ClO4)2 or Mg(NO3)2 enhances the sensitivity of the polymer and therefore the responsiveness of switches and sensors based on PNIPMAM thin films. It is found that Mg(NO3)2 leads to a higher relative water uptake and therefore achieves the highest thickness gain in the swollen state. Y1 - 2023 U6 - https://doi.org/10.1021/acs.macromol.2c02282 SN - 0024-9297 SN - 1520-5835 VL - 56 IS - 2 SP - 567 EP - 577 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Geiger, Christina A1 - Reitenbach, Julija A1 - Henschel, Cristiane A1 - Kreuzer, Lucas A1 - Widmann, Tobias A1 - Wang, Peixi A1 - Mangiapia, Gaetano A1 - Moulin, Jean-François A1 - Papadakis, Christine M. A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter T1 - Ternary nanoswitches realized with multiresponsive PMMA-b-PNIPMAM films in mixed water/acetone vapor atmospheres JF - Advanced engineering materials N2 - To systematically add functionality to nanoscale polymer switches, an understanding of their responsive behavior is crucial. Herein, solvent vapor stimuli are applied to thin films of a diblock copolymer consisting of a short poly(methyl methacrylate) (PMMA) block and a long poly(N-isopropylmethacrylamide) (PNIPMAM) block for realizing ternary nanoswitches. Three significantly distinct film states are successfully implemented by the combination of amphiphilicity and co-nonsolvency effect. The exposure of the thin films to nitrogen, pure water vapor, and mixed water/acetone (90 vol%/10 vol%) vapor switches the films from a dried to a hydrated (solvated and swollen) and a water/acetone-exchanged (solvated and contracted) equilibrium state. These three states have distinctly different film thicknesses and solvent contents, which act as switch positions "off," "on," and "standby." For understanding the switching process, time-of-flight neutron reflectometry (ToF-NR) and spectral reflectance (SR) studies of the swelling and dehydration process are complemented by information on the local solvation of functional groups probed with Fourier-transform infrared (FTIR) spectroscopy. An accelerated responsive behavior beyond a minimum hydration/solvation level is attributed to the fast build-up and depletion of the hydration shell of PNIPMAM, caused by its hydrophobic moieties promoting a cooperative hydration character. KW - co-nonsolvency KW - diblock copolymers KW - nanoswitches KW - neutron reflectometry KW - thin films Y1 - 2021 U6 - https://doi.org/10.1002/adem.202100191 SN - 1438-1656 SN - 1527-2648 VL - 23 IS - 11 PB - Wiley-VCH CY - Weinheim ER -