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  - 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  - 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  - 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  - 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  - Zhong, Qi
A1  - Metwalli, Ezzeldin
A1  - Kaune, Gunar
A1  - Rawolle, Monika
A1  - Bivigou Koumba, Achille Mayelle
A1  - Laschewsky, André
A1  - Papadakis, Christine M.
A1  - Cubitt, Robert
A1  - Müller-Buschbaum, Peter
T1  - Switching kinetics of thin thermo-responsive hydrogel films of poly(monomethoxy-diethyleneglycol-acrylate) probed with in situ neutron reflectivity
JF  - Soft matter
N2  - The switching kinetics of thin thermo-responsive hydrogel films of poly(monomethoxy-diethyleneglycol-acrylate) (PMDEGA) are investigated. Homogeneous and smooth PMDEGA films with a thickness of 35.9 nm are prepared on silicon substrates by spin coating. As probed with white light interferometry, PMDEGA films with a thickness of 35.9 nm exhibit a phase transition temperature of the lower critical solution temperature (LCST) type of 40 degrees C. In situ neutron reflectivity is performed to investigate the thermo-responsive behavior of these PMDEGA hydrogel films in response to a sudden thermal stimulus in deuterated water vapor atmosphere. The collapse transition proceeds in a complex way which can be seen as three steps. The first step is the shrinkage of the initially swollen film by a release of water. In the second step the thickness remains constant with water molecules embedded in the film. In the third step, perhaps due to a conformational rearrangement of the collapsed PMDEGA chains, water is reabsorbed from the vapor atmosphere, thereby giving rise to a relaxation process. Both the shrinkage and relaxation processes can be described by a simple model of hydrogel deswelling.
Y1  - 2012
U6  - https://doi.org/10.1039/c2sm25401h
SN  - 1744-683X
VL  - 8
IS  - 19
SP  - 5241
EP  - 5249
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  - Wang, Peixi
A1  - Geiger, Christina
A1  - Kreuzer, Lucas
A1  - Widmann, Tobias
A1  - Reitenbach, Julija
A1  - Liang, Suzhe
A1  - Cubitt, Robert
A1  - Henschel, Cristiane
A1  - Laschewsky, André
A1  - Papadakis, Christine M.
A1  - Müller-Buschbaum, Peter
T1  - Poly(sulfobetaine)-based diblock copolymer thin films in water/acetone atmosphere: modulation of water hydration and co-nonsolvency-triggered film contraction
JF  - Langmuir : the ACS journal of surfaces and colloids
N2  - The water swelling and subsequent solvent exchange including co-nonsolvency behavior of thin films of a doubly thermo-responsive diblock copolymer (DBC) are studied viaspectral reflectance, time-of-flight neutron reflectometry, and Fourier transform infrared spectroscopy. 
The DBC consists of a thermo-responsive zwitterionic (poly(4-((3-methacrylamidopropyl) dimethylammonio) butane-1-sulfonate)) (PSBP) block, featuring an upper critical solution temperature transition in aqueous media but being insoluble in acetone, and a nonionic poly(N-isopropylmethacrylamide) (PNIPMAM) block, featuring a lower critical solution temperature transition in water, while being soluble in acetone. 
Homogeneous DBC films of 50-100 nm thickness are first swollen in saturated water vapor (H2OorD2O), before they are subjected to a contraction process by exposure to mixed saturated water/acetone vapor (H2OorD2O/acetone-d6 = 9:1 v/v).
The affinity of the DBC film toward H2O is stronger than for D2O, as inferred from the higher film thickness in the swollen state and the higher absorbed water content, thus revealing a pronounced isotope sensitivity. 
During the co-solvent-induced switching by mixed water/acetone vapor, a two-step film contraction is observed, which is attributed to the delayed expulsion of water molecules and uptake of acetone molecules. 
The swelling kinetics are compared for both mixed vapors (H2O/acetone-d6 and D2O/acetone-d6) and with those of the related homopolymer films. 
Moreover, the concomitant variations of the local environment around the hydrophilic groups located in the PSBP and PNIPMAM blocks are followed. 
The first contraction step turns out to be dominated by the behavior of the PSBP block, where as the second one is dominated by the PNIPMAM block. 
The unusual swelling and contraction behavior of the latter block is attributed to its co-nonsolvency behavior. 
Furthermore, we observe cooperative hydration effects in the DBC films, that is, both polymer blocks influence each other's solvation behavior.
Y1  - 2022
U6  - https://doi.org/10.1021/acs.langmuir.2c00451
SN  - 0743-7463
SN  - 1520-5827
VL  - 38
IS  - 22
SP  - 6934
EP  - 6948
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  - 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  -