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 - 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 - 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 - 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 - 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 - Aravopoulou, Dionysia A1 - Kyriakos, Konstantinos A1 - Miasnikova, Anna A1 - Laschewsky, Andre A1 - Papadakis, Christine M. A1 - Kyritsis, Apostolos T1 - Comparative Investigation of the Thermoresponsive Behavior of Two Diblock Copolymers Comprising PNIPAM and PMDEGA Blocks JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - The thermoresponsive behavior of two diblock copolymers PS-b-PNIPAM and PS-b-PMDEGA, which both comprise a hydrophobic polystyrene (PS) block but different thermoresponsive blocks, also differing in length, poly(N-isopropylacrylamide) (PNIPAM) and poly(methoxy diethylene glycol acrylate) (PMDEGA), respectively, was comparatively investigated in a wide temperature range. Concentrated aqueous solutions containing 25 wt % polymer were studied by small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and broadband dielectric spectroscopy (BDS). DSC measurements show that, during the demixing phase transition, the hydration number per oligo(ethylene glycol) side chain in the PS-b-PMDEGA solution decreases rather gradually, even up to 20 °C above the onset of the transition, i.e., the cloud point (CP). In contrast, the PS-b-PNIPAM solution exhibits an abrupt, stepwise dehydration behavior at its CP, indicated by the sharp, narrow endothermic peak. BDS measurements suggest that the organization of the expelled water during the phase transition and the subsequent evolution of the micellar aggregates are different for the two copolymers. In the PS-b-PMDEGA solution, the long-range charge transport process changes significantly at its CP and strong interfacial polarization processes appear, probably due to charge accumulation at the interfaces between the micellar aggregates and the aqueous medium. On the contrary, in the PS-b-PNIPAM solution, the phase transition has only a marginal effect on the long-range conduction process and is accompanied by a reduction in the high-frequency (1 MHz) dielectric permittivity, ε′. The latter effect is attributed to the reduced polarization strength of local chain modes due to an enhancement of intra- and interchain hydrogen bonds (HBs) in the polymer-rich phase during the water detaching process. Surprisingly, our BDS measurements indicate that prior to both the demixing and remixing processes the local chain mobility increases temporally. Our dielectric studies suggest that for PS-b-PNIPAM the water detaching process initiates a few degrees below CP and that the local chain mobility and intra- and/or interchain HBs of the PNIPAM blocks may control its thermoresponsive behavior. Dielectric “jump” experiments show that the kinetics of micellar aggregation in the PS-b-PMDEGA solution is slower than that in the PS-b-PNIPAM solution and is independent of the target temperature within the two-phase region. From the experimental point of view, it is shown that the dielectric susceptibility, especially, the dielectric permittivity, ε′, is a well-suited probe for monitoring both the reversible changes in the molecular dipolar bond polarizability and the long-range interfacial polarization at the phase transition. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jpcb.7b09647 SN - 1520-6106 VL - 122 IS - 9 SP - 2655 EP - 2668 PB - American Chemical Society CY - Washington 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 - 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 - 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 - 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 -