TY - JOUR A1 - Zhong, Qi A1 - Metwalli, Ezzeldin A1 - Rawolle, Monika A1 - Kaune, Gunar A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, Andre A1 - Papadakis, Christine M. A1 - Cubitt, Robert A1 - Wang, Jiping A1 - Müller-Buschbaum, Peter T1 - Vacuum induced dehydration of swollen poly(methoxy diethylene glycol acrylate) and polystyrene-block-poly(methoxy diethylene glycol acrylate)-block-polystyrene films probed by in-situ neutron reflectivity JF - Polymer : the international journal for the science and technology of polymers N2 - The isothermal vacuum-induced dehydration of thin films made of poly(methoxy diethylene glycol acrylate) (PMDEGA), which were swollen under ambient conditions, is studied. The dehydration behavior of the homopolymer film as well as of a nanostructured film of the amphiphilic triblock copolymer polystyrene-block-poly(methoxy diethylene glycol acrylate)-block-polystyrene, abbreviated as PS-b-PMDEGA-b-PS, are probed, and compared to the thermally induced dehydration behavior of such thin thermo-responsive films when they pass through their LCST-type coil-to globule collapse transition. The dehydration kinetics is followed by in-situ neutron reflectivity measurements. Contrast results from the use of deuterated water. Water content and film thickness are significantly reduced during the process, which can be explained by Schott second order kinetics theory for both films. The water content of the dehydrated equilibrium state from this model is very close to the residual water content obtained from the final static measurements, indicating that residual water still remains in the film even after prolonged exposure to the vacuum. In the PS-b-PMDEGA-b-PS film that shows micro-phase separation, the hydrophobic PS domains modify the dehydration process by hindering the water removal, and thus retarding dehydration by about 30%. Whereas residual water remains tightly bound in the PMDEGA domains, water is completely removed from the PS domains of the block copolymer film. (C) 2017 Elsevier Ltd. All rights reserved. KW - Dehydration KW - Vacuum drying KW - In-situ neutron reflectivity Y1 - 2017 U6 - https://doi.org/10.1016/j.polymer.2017.07.066 SN - 0032-3861 SN - 1873-2291 VL - 124 SP - 263 EP - 273 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kyriakos, Konstantinos A1 - Philipp, Martine A1 - Lin, Che-Hung A1 - Dyakonova, Margarita A1 - Vishnevetskaya, Natalya A1 - Grillo, Isabelle A1 - Zaccone, Alessio A1 - Miasnikova, Anna A1 - Laschewsky, Andre A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Quantifying the Interactions in the Aggregation of Thermoresponsive Polymers: The Effect of Cononsolvency JF - Macromolecular rapid communications N2 - The aggregation kinetics of thermoresponsive core-shell micelles with a poly(N-isopropyl acrylamide) shell in pure water or in mixtures of water with the cosolvents methanol or ethanol at mole fractions of 5% is investigated during a temperature jump across the respective cloud point. Characteristically, these mixtures give rise to cononsolvency behavior. At the cloud point, aggregates are formed, and their growth is followed with time-resolved small-angle neutron scattering. Using the reversible association model, the interaction potential between the aggregates is determined from their growth rate in dependence on the cosolvents. The effect of the cosolvent is attributed to the interaction potential on the structured layer of hydration water around the aggregates. It is surmised that the latter is perturbed by the cosolvent and thus the residual repulsive hydration force between the aggregates is reduced. The larger the molar volume of the cosolvent, the more pronounced is the effect. This framework provides a molecular-level understanding of solvent-mediated effective interactions in polymer solutions and new opportunities for the rational control of self-assembly in complex soft matter systems. KW - colloidal aggregation KW - cononsolvency KW - interaction potential KW - polymer solutions KW - self-assembled micelles KW - thermoresponsive polymers Y1 - 2016 U6 - https://doi.org/10.1002/marc.201500583 SN - 1022-1336 SN - 1521-3927 VL - 37 SP - 420 EP - 425 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Zhong, Qi A1 - Metwalli, Ezzeldin A1 - Rawolle, Monika A1 - Kaune, Gunar A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, Andre A1 - Papadakis, Christine M. A1 - Cubitt, Robert A1 - Wang, Jiping A1 - Müller-Buschbaum, Peter T1 - Influence of Hydrophobic Polystyrene Blocks on the Rehydration of Polystyrene-block-poly(methoxy diethylene glycol acrylate)-block-polystyrene Films Investigated by in Situ Neutron Reflectivity JF - Macromolecules : a publication of the American Chemical Society N2 - The rehydration of thermoresponsive polystyrene-block-poly(methoxy diethylene glycol acrylate)-block-polystyrene (PS-b-PMDEGA-b-PS) films forming a lamellar microphase-separated structure is investigated by in situ neutron reflectivity in a D2O vapor atmosphere. The rehydration of collapsed PS-b-PMDEGA-b-PS films is realized by a temperature change from 45 to 23 degrees C and comprises (1) condensation and absorption of D2O, (2) evaporation of D2O, and (3) reswelling of the film due to internal rearrangement. The hydrophobic PS layers hinder the absorption of condensed D2O, and a redistribution of embedded D2O between the hydrophobic PS layers and the hydrophilic PMDEGA layers is observed. In contrast, the rehydration of semiswollen PS-b-PMDEGA-b-PS films (temperature change from 35 to 23 degrees C) shows two prominent differences: A thicker D2O layer condenses on the surface, causing a more enhanced evaporation of D2O. The rehydrated films differ in film thickness and volume fraction of D2O, which is due to the different thermal protocols, although the final temperature is identical. Y1 - 2016 U6 - https://doi.org/10.1021/acs.macromol.5b02279 SN - 0024-9297 SN - 1520-5835 VL - 49 SP - 317 EP - 326 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Nieuwenhuis, Sophie A1 - Zhong, Qi A1 - Metwalli, Ezzeldin A1 - Biessmann, Lorenz A1 - Philipp, Martine A1 - Miasnikova, Anna A1 - Laschewsky, Andre A1 - Papadakis, Christine M. A1 - Cubitt, Robert A1 - Wang, Jiping A1 - Müller-Buschbaum, Peter T1 - Hydration and Dehydration Kinetics: Comparison between Poly(N-isopropyl methacrylamide) and Poly(methoxy diethylene glycol acrylate) Films JF - Langmuir N2 - Thermoresponsive films of poly(N-isopropyl methacrylamide) (PNIPMAM) and poly(methoxy diethylene glycol acrylate) (PMDEGA) are compared with respect to their hydration and dehydration kinetics using in situ neutron reflectivity. Both as-prepared films present a homogeneous single-layer structure and have similar transition temperatures of the lower critical solution temperature type (TT, PNIPMAM 38 degrees C and PMDEGA 41 degrees C). After hydration in unsaturated D2O vapor at 23 degrees C, a D2O enrichment layer is observed in PNIPMAM films adjacent to the Si substrate. In contrast, two enrichment layers are present in PMDEGA films (close to the vapor interface and the Si substrate). PNIPMAM films exhibit a higher hydration capability, ascribed to having both donor (N-H) and acceptor (C=O) units for hydrogen bonds. "While the swelling of the PMDEGA films is mainly caused by the increase of the enrichment layers, the thickness of the entire PNIPMAM films increases with time. The observed longer relaxation time for swelling of PNIPMAM films is attributed to the much higher glass transition temperature of PNIPMAM. When dehydrating both films by increasing the temperature above the TT, they react with a complex response consisting of three stages (shrinkage, rearrangement, and reswelling). PNIPMAM films respond faster than PMDEGA films. After dehydration, both films still contain a large amount of D2O, and no completely dry film state is reached for a temperature above their TTs. Y1 - 2019 U6 - https://doi.org/10.1021/acs.langmuir.9b00535 SN - 0743-7463 VL - 35 IS - 24 SP - 7691 EP - 7702 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Hildebrand, Viet A1 - Heydenreich, Matthias A1 - Laschewsky, Andre A1 - Moeller, Heiko M. A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. A1 - Schanzenbach, Dirk A1 - Wischerhoff, Erik T1 - "Schizophrenic" self-assembly of dual thermoresponsive block copolymers bearing a zwitterionic and a non-ionic hydrophilic block JF - Polymer : the international journal for the science and technology of polymers N2 - Several series of presumed dual thermo-responsive diblock copolymers consisting of one non-ionic and one zwitterionic block were synthesized via consecutive reversible addition-fragmentation chain transfer (RAFT) polymerization. For all copolymers, poly(N-isopropylmethacrylamide) was chosen as non-ionic block that shows a coil-to-globule collapse transition of the lower critical solution temperature (LCST) type. In contrast, the chemical structure of zwitterionic blocks, which all belonged to the class of poly(sulfobetaine methacrylate)s, was varied broadly, in order to tune their coil-to-globule collapse transition of the upper critical solution temperature (UCST) type. All polymers were labeled with a solvatochromic fluorescent end-group. The dual thermo-responsive behavior and the resulting multifarious temperature-dependent self-assembly in aqueous solution were mapped by temperature resolved turbidimetry, H-1 NMR spectroscopy, dynamic light scattering (DLS), and fluorescence spectroscopy. Depending on the relative positions between the UCST-type and LCST-type transition temperatures, as well as on the width of the window in-between, all the four possible modes of stimulus induced micellization can be realized. This includes classical induced micellization due to a transition from a double hydrophilic, or respectively, from a double hydrophobic to an amphiphilic state, as well as "schizophrenic" behavior, where the core- and shell-forming blocks are inverted. The exchange of the roles of the hydrophilic and hydrophobic block in the amphiphilic states is possible through a homogeneous intermediate state or a heterogeneous one. (C) 2017 Elsevier Ltd. All rights reserved. KW - RAFT polymerization KW - Block copolymer KW - Sulfobetaine methacrylate KW - Responsive polymer KW - LCST KW - UCST KW - Schizophrenic self-assembly Y1 - 2017 U6 - https://doi.org/10.1016/j.polymer.2017.06.063 SN - 0032-3861 SN - 1873-2291 VL - 122 SP - 347 EP - 357 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Papadakis, Christine M. A1 - Müller-Buschbaum, Peter A1 - Laschewsky, Andre T1 - Switch It Inside-Out: "Schizophrenic" Behavior of All Thermoresponsive UCST-LCST Diblock Copolymers JF - Langmuir N2 - This feature article reviews our recent advancements on the synthesis, phase behavior, and micellar structures of diblock copolymers consisting of oppositely thermoresponsive blocks in aqueous environments. These copolymers combine a nonionic block, which shows lower critical solution temperature (LCST) behavior, with a zwitterionic block that exhibits an upper critical solution temperature (UCST). The transition temperature of the latter class of polymers is strongly controlled by its molar mass and by the salt concentration, in contrast to the rather invariant transition of nonionic polymers with type II LCST behavior such as poly(N-isopropylacrylamide) or poly(N-isopropyl methacrylamide). This allows for implementing the sequence of the UCST and LCST transitions of the polymers at will by adjusting either molecular or, alternatively, physical parameters. Depending on the location of the transition temperatures of both blocks, different switching scenarios are realized from micelles to inverse micelles, namely via the molecularly dissolved state, the aggregated state, or directly. In addition to studies of (semi)dilute aqueous solutions, highly concentrated systems have also been explored, namely water-swollen thin films. Concerning applications, we discuss the possible use of the diblock copolymers as "smart" nanocarriers. Y1 - 2019 U6 - https://doi.org/10.1021/acs.langmuir.9b01444 SN - 0743-7463 VL - 35 IS - 30 SP - 9660 EP - 9676 PB - American Chemical Society CY - Washington 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 - "Schizophrenic" Micelles from Doubly Thermoresponsive Polysulfobetaine-b-poly(N-isopropylmethacrylamide) Diblock Copolymers JF - Macromolecules : a publication of the American Chemical Society Y1 - 2017 U6 - https://doi.org/10.1021/acs.macromol.7b00356 SN - 0024-9297 SN - 1520-5835 VL - 50 SP - 3985 EP - 3999 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Vishnevetskaya, Natalya S. A1 - Hildebrand, Viet A1 - Dyakonova, Margarita A. A1 - Niebuur, Bart-Jan A1 - Kyriakos, Konstantinos A1 - Raftopoulos, Konstantinos N. A1 - Di, Zhenyu A1 - Müller-Buschbaum, Peter A1 - Laschewsky, Andre A1 - Papadakis, Christine M. T1 - Dual orthogonal switching of the "Schizophrenic" self-assembly of diblock copolymers JF - Macromolecules : a publication of the American Chemical Society N2 - Based on diblock copolymers, a pair of "schizophrenic" micellar systems is designed by combining a nonionic and thermoresponsive block with a zwitterionic block, which is thermoresponsive and salt-sensitive. The nonionic block is poly(N-isopropylacrylamide) (PNIPAM) or poly(N-isopropylmethacrylamide) (PNIPMAM) and exhibits a lower critical solution temperature (LCST) behavior in aqueous solution. The zwitterionic block is a polysulfobetaine, i.e., poly(4((3-methacrylamidopropyl)dimethylammonio)butane-1-sulfonate) (PSBP), and has an upper critical solution temperature (UCST) behavior with the clearing point decreasing with increasing salt concentration. The PSBP-b-PNIPAM and PSBP-b-PNIPMAM diblock copolymers are prepared by successive reversible addition-fragmentation chain transfer (RAFT) polymerizations. The PSBP block is chosen such that the clearing point of the homopolymer is significantly higher in pure water than the cloud point of PNIPAM or PNIPMAM. Using turbidimetry, H-1 NMR, and small-angle neutron scattering, we investigate the overall phase behavior as well as the structure and interaction between the micelles and the intermediate phase, both in salt-free D2O and in 0.004 M NaBr in D2O in a wide temperature range. We find that PSBP-b-PNIPAM at 50 g L-1 in salt-free D2O is turbid in the entire temperature range. It forms spherical micelles below the cloud point of PNIPAM and cylindrical micelles above. Similar behavior is observed for PSBP-b-PNIPMAM at 50 g L-1 in salt-free D2O with a slight and smooth increase of the light transmission below the cloud point of PNIPMAM and an abrupt decrease above. Upon addition of 0.004 M NaBr, the UCST-type cloud point of the PSBP-block is notably decreased, and an intermediate regime is encountered below the cloud point of PNIPMAM, where the light transmission is slightly enhanced. In this regime, the polymer solution exhibits behavior typical for polyelectrolyte solutions. Thus, double thermosensitive and salt-sensitive behavior with "schizophrenic" micelle formation is found, and the width of the intermediate regime, where both blocks are hydrophilic, can be tuned by the addition of electrolyte. Y1 - 2018 U6 - https://doi.org/10.1021/acs.macromol.8b00096 SN - 0024-9297 SN - 1520-5835 VL - 51 IS - 7 SP - 2604 EP - 2614 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Vishnevetskaya, Natalya S. A1 - Hildebrand, Viet A1 - Nizardo, Noverra Mardhatillah A1 - Ko, Chia-Hsin A1 - Di, Zhenyu A1 - Radulescu, Aurel A1 - Barnsley, Lester C. A1 - Müller-Buschbaum, Peter A1 - Laschewsky, André A1 - Papadakis, Christine M. T1 - All-in-One "Schizophrenic" self-assembly of orthogonally tuned thermoresponsive diblock copolymers JF - Langmuir N2 - Smart, fully orthogonal switching was realized in a highly biocompatible diblock copolymer system with variable trigger-induced aqueous self-assembly. The polymers are composed of nonionic and zwitterionic blocks featuring lower and upper critical solution temperatures (LCSTs and UCSTs). In the system investigated, diblock copolymers from poly(N-isopropyl methacrylamide) (PNIPMAM) and a poly(sulfobetaine methacrylamide), systematic variation of the molar mass of the latter block allowed for shifting the UCST of the latter above the LCST of the PNIPMAM block in a salt-free condition. Thus, successive thermal switching results in "schizophrenic" micellization, in which the roles of the hydrophobic core block and the hydrophilic shell block are interchanged depending on the temperature. Furthermore, by virtue of the strong electrolyte-sensitivity of the zwitterionic polysulfobetaine block, we succeeded to shift its UCST below the LCST of the PNIPMAM block by adding small amounts of an electrolyte, thus inverting the pathway of switching. This superimposed orthogonal switching by electrolyte addition enabled us to control the switching scenarios between the two types of micelles (i) via an insoluble state, if the LCST-type cloud point is below the UCST-type cloud point, which is the case at low salt concentrations or (ii) via a molecularly dissolved state, if the LCST-type cloud point is above the UCST-type cloud point, which is the case at high salt concentrations. Systematic variation of the block lengths allowed for verifying the anticipated behavior and identifying the molecular architecture needed. The versatile and tunable self-assembly offers manifold opportunities, for example, for smart emulsifiers or for sophisticated carrier systems. Y1 - 2019 U6 - https://doi.org/10.1021/acs.langmuir.9b00241 SN - 0743-7463 VL - 35 IS - 19 SP - 6441 EP - 6452 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zhong, Qi A1 - Mi, Lei A1 - Metwalli, Ezzeldin A1 - Biessmann, Lorenz A1 - Philipp, Martine A1 - Miasnikova, Anna A1 - Laschewsky, Andre A1 - Papadakis, Christine M. A1 - Cubitt, Robert A1 - Schwartzkopf, Matthias A1 - Roth, Stephan V. A1 - Wang, Jiping A1 - Müller-Buschbaum, Peter T1 - Effect of chain architecture on the swelling and thermal response of star-shaped thermo-responsive (poly(methoxy diethylene glycol acrylate)-block-polystyrene)(3) block copolymer films JF - Soft matter N2 - The effect of chain architecture on the swelling and thermal response of thin films obtained from an amphiphilic three-arm star-shaped thermo-responsive block copolymer poly(methoxy diethylene glycol acrylate)-block-polystyrene ((PMDEGA-b-PS)(3)) is investigated by in situ neutron reflectivity (NR) measurements. The PMDEGA and PS blocks are micro-phase separated with randomly distributed PS nanodomains. The (PMDEGA-b-PS)(3) films show a transition temperature (TT) at 33 degrees C in white light interferometry. The swelling capability of the (PMDEGA-b-PS)(3) films in a D2O vapor atmosphere is better than that of films from linear PS-b-PMDEGA-b-PS triblock copolymers, which can be attributed to the hydrophilic end groups and limited size of the PS blocks in (PMDEGA-b-PS)(3). However, the swelling kinetics of the as-prepared (PMDEGA-b-PS)(3) films and the response of the swollen film to a temperature change above the TT are significantly slower than that in the PS-b-PMDEGA-b-PS films, which may be related to the conformation restriction by the star-shape. Unlike in the PS-b-PMDEGA-b-PS films, the amount of residual D2O in the collapsed (PMDEGA-b-PS)(3) films depends on the final temperature. It decreases from (9.7 +/- 0.3)% to (7.0 +/- 0.3)% or (6.0 +/- 0.3)% when the final temperatures are set to 35 degrees C, 45 degrees C and 50 degrees C, respectively. This temperature-dependent reduction of embedded D2O originates from the hindrance of chain conformation from the star-shaped chain architecture. Y1 - 2018 U6 - https://doi.org/10.1039/c8sm00965a SN - 1744-683X SN - 1744-6848 VL - 14 IS - 31 SP - 6582 EP - 6594 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Kreuzer, Lucas A1 - Widmann, Tobias A1 - Hohn, Nuri A1 - Wang, Kun A1 - Biessmann, Lorenz A1 - Peis, Leander A1 - Moulin, Jean-Francois A1 - Hildebrand, Viet A1 - Laschewsky, André A1 - Papadakis, Christine M. A1 - Müller-Buschbaum, Peter T1 - Swelling and exchange behavior of poly(sulfobetaine)-based block copolymer thin films JF - Macromolecules : web edition N2 - The humidity-induced swelling and exchange behavior of a block copolymer thin film, which consists of a zwitterionic poly(sulfobetaine) [poly(N,N-dimethyl-N-(3-(methacrylamido)propyl)ammoniopropanesulfonate) (PSPP)] block and a nonionic poly(N-isopropylacrylamide) (PNIPAM) block, are investigated by time-of-flight neutron reflectometry (TOF-NR). We monitor in situ the swelling in the H2O atmosphere, followed by an exchange with D2O. In the reverse experiment, swelling in the D2O atmosphere and the subsequent exchange with H2O are studied. Both, static and kinetic TOF-NR measurements indicate significant differences in the interactions between the PSPP80-b-PNIPAM(130) thin film and H2O or D2O, which we attribute to the different H- and D-bonds between water and the polymer. Changes in the chain conformation and hydrogen bonding are probed with Fourier transform infrared spectroscopy during the kinetics of the swelling and exchange processes, which reveals the key roles of the ionic SO3- group in the PSPP block and of the polar amide groups of both blocks during water uptake and exchange. Y1 - 2019 U6 - https://doi.org/10.1021/acs.macromol.9b00443 SN - 0024-9297 SN - 1520-5835 VL - 52 IS - 9 SP - 3486 EP - 3498 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Lai, Huagui A1 - Luo, Jincheng A1 - Zwirner, Yannick A1 - Olthof, Selina A1 - Wieczorek, Alexander A1 - Ye, Fangyuan A1 - Jeangros, Quentin A1 - Yin, Xinxing A1 - Akhundova, Fatima A1 - Ma, Tianshu A1 - He, Rui A1 - Kothandaraman, Radha K. A1 - Chin, Xinyu A1 - Gilshtein, Evgeniia A1 - Muller, Andre A1 - Wang, Changlei A1 - Thiesbrummel, Jarla A1 - Siol, Sebastian A1 - Prieto, Jose Marquez A1 - Unold, Thomas A1 - Stolterfoht, Martin A1 - Chen, Cong A1 - Tiwari, Ayodhya N. A1 - Zhao, Dewei A1 - Fu, Fan T1 - High-performance flexible all-Perovskite tandem solar cells with reduced V-OC-deficit in wide-bandgap subcell JF - Advanced energy materials N2 - Among various types of perovskite-based tandem solar cells (TSCs), all-perovskite TSCs are of particular attractiveness for building- and vehicle-integrated photovoltaics, or space energy areas as they can be fabricated on flexible and lightweight substrates with a very high power-to-weight ratio. However, the efficiency of flexible all-perovskite tandems is lagging far behind their rigid counterparts primarily due to the challenges in developing efficient wide-bandgap (WBG) perovskite solar cells on the flexible substrates as well as their low open-circuit voltage (V-OC). Here, it is reported that the use of self-assembled monolayers as hole-selective contact effectively suppresses the interfacial recombination and allows the subsequent uniform growth of a 1.77 eV WBG perovskite with superior optoelectronic quality. In addition, a postdeposition treatment with 2-thiopheneethylammonium chloride is employed to further suppress the bulk and interfacial recombination, boosting the V-OC of the WBG top cell to 1.29 V. Based on this, the first proof-of-concept four-terminal all-perovskite flexible TSC with a power conversion efficiency of 22.6% is presented. When integrating into two-terminal flexible tandems, 23.8% flexible all-perovskite TSCs with a superior V-OC of 2.1 V is achieved, which is on par with the V-OC reported on the 28% all-perovskite tandems grown on the rigid substrate. KW - all-perovskite tandems KW - flexible tandem solar cells KW - perovskite KW - V OC-deficit KW - wide-bandgap Y1 - 2022 U6 - https://doi.org/10.1002/aenm.202202438 SN - 1614-6832 SN - 1614-6840 VL - 12 IS - 45 PB - Wiley-VCH CY - Weinheim ER -