@article{ZhongMetwalliRawolleetal.2015, author = {Zhong, Qi and Metwalli, Ezzeldin and Rawolle, Monika and Kaune, Gunar and Bivigou Koumba, Achille Mayelle and Laschewsky, Andr{\´e} and Papadakis, Christine M. and Cubitt, Robert and M{\"u}ller-Buschbaum, Peter}, title = {Rehydration of Thermoresponsive Poly(monomethoxydiethylene glycol acrylate) Films Probed in Situ by Real-Time Neutron Reflectivity}, series = {Macromolecules : a publication of the American Chemical Society}, volume = {48}, journal = {Macromolecules : a publication of the American Chemical Society}, number = {11}, publisher = {American Chemical Society}, address = {Washington}, issn = {0024-9297}, doi = {10.1021/acs.macromol.5b00645}, pages = {3604 -- 3612}, year = {2015}, abstract = {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.}, language = {en} } @article{ZhongMetwalliRawolleetal.2013, author = {Zhong, Qi and Metwalli, Ezzeldin and Rawolle, Monika and Kaune, Gunar and Bivigou Koumba, Achille Mayelle and Laschewsky, Andr{\´e} and Papadakis, Christine M. and Cubitt, Robert and M{\"u}ller-Buschbaum, Peter}, title = {Structure and Thermal Response of Thin Thermoresponsive Polystyrene-block-poly(methoxydiethylene glycol acrylate)-block-polystyrene Films}, series = {Macromolecules : a publication of the American Chemical Society}, volume = {46}, journal = {Macromolecules : a publication of the American Chemical Society}, number = {10}, publisher = {American Chemical Society}, address = {Washington}, issn = {0024-9297}, doi = {10.1021/ma400627u}, pages = {4069 -- 4080}, year = {2013}, abstract = {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.}, language = {en} } @article{ZhongMetwalliKauneetal.2012, author = {Zhong, Qi and Metwalli, Ezzeldin and Kaune, Gunar and Rawolle, Monika and Bivigou Koumba, Achille Mayelle and Laschewsky, Andr{\´e} and Papadakis, Christine M. and Cubitt, Robert and M{\"u}ller-Buschbaum, Peter}, title = {Switching kinetics of thin thermo-responsive hydrogel films of poly(monomethoxy-diethyleneglycol-acrylate) probed with in situ neutron reflectivity}, series = {Soft matter}, volume = {8}, journal = {Soft matter}, number = {19}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1744-683X}, doi = {10.1039/c2sm25401h}, pages = {5241 -- 5249}, year = {2012}, abstract = {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.}, language = {en} } @article{ZhongAdelsbergerNiedermeieretal.2013, author = {Zhong, Qi and Adelsberger, Joseph and Niedermeier, M. A. and Golosova, Anastasi and Bivigou Koumba, Achille Mayelle and Laschewsky, Andr{\´e} and Funari, S. S. and Papadakis, Christine M. and M{\"u}ller-Buschbaum, Peter}, title = {The influence of selective solvents on the transition behavior of poly(styrene-b-monomethoxydiethylenglycol-acrylate-b-styrene) thick films}, series = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft}, volume = {291}, journal = {Colloid and polymer science : official journal of the Kolloid-Gesellschaft}, number = {6}, publisher = {Springer}, address = {New York}, issn = {0303-402X}, doi = {10.1007/s00396-012-2879-4}, pages = {1439 -- 1451}, year = {2013}, abstract = {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.}, language = {en} } @article{ZerballLaschewskyvonKlitzing2015, author = {Zerball, Maximilian and Laschewsky, Andr{\´e} and von Klitzing, Regine}, title = {Swelling of Polyelectrolyte Multilayers: The Relation Between, Surface and Bulk Characteristics}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {119}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {35}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/acs.jpcb.5b04350}, pages = {11879 -- 11886}, year = {2015}, abstract = {The odd even effect, i.e., the influence of the outermost layer of polyelectrolyte multilayers (PEMs) on their swelling behavior, is investigated. For that purpose poly(styrene sodium sulfonate) (PSS)/poly(diallyl-dimethylammonium chloride) (PDADMAC) polyelectrolyte multilayers are studied in air with 1\% relative humidity (RH), 30\% RH, 95\% RH, and in liquid water by ellipsometry, atomic force microscopy (AFM), and X-ray reflectometry (XRR). Since the total amount of water uptake in swollen PEMs is divided into two fractions, the void water and the swelling water, a correct evaluation of the odd even effect is only possible if both fractions are examined separately. In order to allow measuring samples over a larger thickness regime the investigation of a larger amount of samples is required. Therefore, the concept of separating void water from swelling water using neutron reflectometry is for the first time transferred to ellipsometry. The subsequent analysis of swelling water, void water, and roughness revealed the existence of two types of odd even effects: an odd even effect which addresses only the surface of the PEM (surface-odd even effect) and an odd even effect which addresses also the bulk of the PEM (bulk-odd even effect). The appearance of both effects is dependent on the environment; the surface-odd even effect is only detectable in humid air while the bulk-odd even effect is only detectable in liquid water. The bulk-odd even effect is related to the osmotic pressure between the PEM and the surrounding water. A correlation between the amount of void water and both odd even effects is not found. The amount of void water is independent of the terminated layer and the thickness of PEMs.}, language = {en} } @article{ZehmLaschewskyLiangetal.2011, author = {Zehm, Daniel and Laschewsky, Andr{\´e} and Liang, Hua and Rabe, J{\"u}rgen P.}, title = {Straightforward access to amphiphilic dual bottle brushes by combining RAFT, ATRP, and NMP polymerization in one sequence}, series = {Macromolecules : a publication of the American Chemical Society}, volume = {44}, journal = {Macromolecules : a publication of the American Chemical Society}, number = {24}, publisher = {American Chemical Society}, address = {Washington}, issn = {0024-9297}, doi = {10.1021/ma2015613}, pages = {9635 -- 9641}, year = {2011}, abstract = {Molecular brush diblock copolymers were synthesized by the orthogonal overlay of the RAFT (reversible addition-fragmentation chain transfer), the ATRP (atom transfer radical polymerization), and the NMP (nitroxide-mediated polymerization) techniques. This unique combination enabled the synthesis of the complex amphiphilic polymers without the need of postpolymerization modifications, using a diblock copolymer intermediate made from two selectively addressable inimers and applying a sequence of four controlled free radical polymerization steps in total. The resulting polymers are composed of a thermosensitive poly(N-isopropylacrylamide) brush as hydrophilic block and a polystyrene brush as hydrophobic block, thus translating the structure of the established amphiphilic diblock copolymers known as macro surfactants to the higher size level of "giant surfactants". The dual molecular brushes and the aggregates formed on ultra flat solid substrates were visualized by scanning force microscopy (SFM).}, language = {en} } @article{ZehmLaschewskyHeunemannetal.2011, author = {Zehm, Daniel and Laschewsky, Andr{\´e} and Heunemann, Peggy and Gradzielski, Michael and Prevost, Sylvain and Liang, Hua and Rabe, J{\"u}rgen P. and Lutz, Jean-Francois}, title = {Synthesis and self-assembly of amphiphilic semi-brush and dual brush block copolymers in solution and on surfaces}, series = {Polymer Chemistry}, volume = {2}, journal = {Polymer Chemistry}, number = {1}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1759-9954}, doi = {10.1039/c0py00200c}, pages = {137 -- 147}, year = {2011}, abstract = {The combination of two techniques of controlled free radical polymerization, namely the reversible addition fragmentation chain transfer (RAFT) and the atom transfer radical polymerization (ATRP) techniques, together with the use of a macromonomer allowed the synthesis of symmetrical triblock copolymers, designed as amphiphilic dual brushes. One type of brush was made of poly(n-butyl acrylate) as soft hydrophobic block, i.e. characterized by a low glass transition temperature, while the other one was made of hydrophilic poly(ethylene glycol) (PEG). The new triblock polymers represent "giant surfactants" according to their molecular architecture. The hydrophobic and hydrophilic blocks microphase separate in the bulk. In aqueous solution, they aggregate into globular micellar aggregates, their size being determined by the length of the stretched polymer molecules. As determined by the combination of various scattering techniques for the dual brush copolymer, a rather compact structure is formed, which is dominated by the large hydrophobic poly(n-butyl acrylate) block. The aggregation number for the dual brush is about 10 times larger than for the "semi-brush" precursor copolymer, due to the packing requirements for the much bulkier hydrophobic core. On mica surfaces the triblock copolymers adsorb with worm-like backbones and stretched out side chains.}, language = {en} } @article{ZehmLaschewskyGradzielskietal.2010, author = {Zehm, Daniel and Laschewsky, Andr{\´e} and Gradzielski, Michael and Pr{\´e}vost, Sylvain and Liang, Hua and Rabe, J{\"u}rgen P. and Schweins, Ralf and Gummel, J{\´e}r{\´e}mie}, title = {Amphiphilic dual brush block copolymers as "giant surfactants" and their aqueous self-assembly}, issn = {0743-7463}, doi = {10.1021/La903087p}, year = {2010}, abstract = {Amphiphilic dual brush diblock as well as symmetrical triblock polymers were synthesized by the overlay of the reversible addition-fragmentation chain transfer and the nitroxide mediated polymerization (NMP) techniques. While poly(ethylene glycol) brushes served as hydrophilic block, the hydrophobic block was made of polystyrene brushes. The resulting "giant surfactants" correspond structurally to the established amphiphilic diblock and triblock copolymer known as macrosurfactants. The aggregation behavior of the novel "giant surfactants" in aqueous solution was studied by dynamic light scattering, small-angle neutron scattering (SANS), and small-angle X-ray scattering (SAXS) over a large range in reciprocal space. Further, the self-assembled aggregates Were investigated by scanning force microscopy (SFM) after deposition on differently functionalized ultraflat solid substrates. Despite the high fraction of hydrophobic segments, the polymers form stable mesoscopic, spherical aggregates with hydrodynamic diameters in the range of 150-350 nm. Though prepared from well-defined individual polymers, the aggregates show several similarities to hard core latexes. They are stable enough to he deposited without much changes onto surfaces, where they cluster and show Spontaneous sorting according to their size within the clusters, with the larger aggregates being in the center.}, language = {en} } @article{YuillaumeGlinelJonasetal.2003, author = {Yuillaume, P. Y. and Glinel, Karine and Jonas, Alain M. and Laschewsky, Andr{\´e}}, title = {Ordered polyelectrolyte "Multilayers" : 6. Effect of the molecular parameters on the formation of hybrid multilayers complexing poly(diallylammonium) salt and exfoliated clay}, year = {2003}, language = {en} } @article{WischerhoffGlatzelUhligetal.2009, author = {Wischerhoff, Erik and Glatzel, Stefan and Uhlig, Katja and Lankenau, Andreas and Lutz, Jean-Francois and Laschewsky, Andr{\´e}}, title = {Tuning the thickness of polymer brushes grafted from nonlinearly growing multilayer assemblies}, issn = {0743-7463}, doi = {10.1021/La804197j}, year = {2009}, abstract = {A new versatile method for tuning the thickness of surface-tethered polymer brushes is introduced. It is based on the combination of polyelectrolyte multilayer deposition and surface-initiated atom transfer radical polymerization. To control the thickness of the brushes, the nonlinear growth of certain polyelectrolyte multilayer systems is exploited. The method is demonstrated to work with different polyelectrolytes and different monomers. The relevance for applications is demonstrated by cell adhesion experiments oil grafted thermoresponsive polymer layers with varying thickness.}, language = {en} }