References of "Philipp, Martine 40000526"
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See detailMolecular versus macroscopic perspective on the demixing transition of aqueous PNIPAM solutions by studying the dual character of the refractive index
Philipp, Martine UL; Aleksandrova, Ralitsa UL; Müller, Ulrich UL et al

in Soft Matter (2014), 10(37), 7297-7305

The phase separation of aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions is known to strongly affect their volume expansion behaviour and the elastic moduli, as the latter are strongly coupled to ... [more ▼]

The phase separation of aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions is known to strongly affect their volume expansion behaviour and the elastic moduli, as the latter are strongly coupled to the macroscopic order parameter. On the molecular scale, considerable changes in H-bonding and hydrophobic interactions, as well as in the structure govern the demixing process. However, the relationship between the molecular and macroscopic order parameters is unclear for such complex phase-separating solutions. We contribute to the clarification of this problem by relating optical to volumetric properties across the demixing transition of dilute to concentrated aqueous PNIPAM solutions. Far from the demixing temperature, the temperature dependence of the refractive index is predominantly determined by thermal expansion. In the course of phase separation, the refractive index is dominated by the anomalous behaviour of the specific refractivity, which reflects the spatio-temporally averaged changes in molecular interactions and the structural reorganization of the demixing solutions. Moreover, the presence of relaxation processes is studied by the complex expansion coefficient using the novel technique of temperature modulated optical refractometry. [less ▲]

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See detailFrom Molecular Dehydration to Excess Volumes of Phase-Separating PNIPAM Solutions
Philipp, Martine UL; Kyriakos, Konstantinos; Silvi, Luca et al

in Journal of Physical Chemistry B (2014), 118

For aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions, a structural instability leads to the collapse and aggregation of the macromolecules at the temperature-induced demixing transition. The ... [more ▼]

For aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions, a structural instability leads to the collapse and aggregation of the macromolecules at the temperature-induced demixing transition. The accompanying cooperative dehydration of the PNIPAM chains is known to play a crucial role in this phase separation. We elucidate the impact of partial dehydration of PNIPAM on the volume changes related to the phase separation of dilute to concentrated PNIPAM solutions. Quasi-elastic neutron scattering enables us to directly follow the isotropic jump diffusion behavior of the hydration water and the almost freely diffusing water. As the hydration number decreases from 8 to 2 for the demixing 25 mass % PNIPAM solution, only a partial dehydration of the PNIPAM chains occurs. Dilatation studies reveal that the transition-induced volume changes depend in a remarkable manner on the PNIPAM concentration of the solutions. The excess volume per mole of H2O molecules expelled from the solvation layers of PNIPAM during phase separation probably strongly increases from dilute to concentrated PNIPAM solutions. This finding is qualitatively related to the immense strain-softening previously observed for demixing PNIPAM solutions. [less ▲]

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See detailImmense elastic nonlinearities at the demixing transition of aqueous PNIPAM solutions
Philipp, Martine UL; Müller, Ulrich UL; Aleksandrova, Ralitsa UL et al

in Soft Matter (2013), 9

Elastic nonlinearities are particularly relevant for soft materials because of their inherently small linear elasticity. Nonlinear elastic properties may even take over the leading role for the ... [more ▼]

Elastic nonlinearities are particularly relevant for soft materials because of their inherently small linear elasticity. Nonlinear elastic properties may even take over the leading role for the transformation at mechanical instabilities accompanying many phase transitions in soft matter. Because of inherent experimental difficulties, only little is known about third order (nonlinear) elastic constants within liquids, gels and polymers. Here we show that a key concept to access third order elasticity in soft materials is the determination of mode Gr¨uneisen parameters. We report the first direct observation of third order elastic constants across mechanical instabilities accompanying the liquid–liquid demixing transition of semi-dilute aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions. Immense elastic nonlinearities, leading to a strong strain-softening in the phase-separating PNIPAM solutions, are observed. Molecular mechanisms, which may be responsible for these immense elastic nonlinearities, are discussed. The importance of third order elastic constants in comparison to second order (linear) elastic constants in the demixing PNIPAM solutions evidences the need to focus more on the general role played by nonlinear elasticity at phase transitions within synthetic and biological liquids and gels. [less ▲]

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See detailKinetic processes at the demixing transition of PNIPAM solutions
Philipp, Martine UL; Müller, Ulrich UL; Jiménez Riobóo et al

in Soft Matter (2013), 9

Kinetic processes, which are joined with mass transport, are studied in the vicinity of the sharp LCST-type demixing transition of semi-dilute aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions ... [more ▼]

Kinetic processes, which are joined with mass transport, are studied in the vicinity of the sharp LCST-type demixing transition of semi-dilute aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions. These processes are slow as compared to the highly cooperative collapse of individual polymer chains. Purely elastic properties, that are particularly sensitive to this phase transition, are addressed depending on the temperature, space and time by Brillouin spectroscopy. Above the demixing temperature Tc, we discriminate between kinetics related to the phase separation into PNIPAM-rich and PNIPAM-poor domains and kinetics connected to the impact of gravitation on the on-going phase separation. Using shallow temperature jumps of 0.3 C, the growth of compact PNIPAM-rich agglomerates with identical gel-like mechanical consistency is provoked independently of temperature and position within the sample above Tc. Astonishingly, the transition temperature does not vary while heating or cooling the solutions across the phase transition, although the elastic properties depend strongly on space and time during the equilibration of PNIPAM concentration gradients following the re-entrance into the lowtemperature phase. [less ▲]

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See detailTemperature modulated optical refractometry: A quasi-isothermal method to determine the dynamic volume expansion coefficient
Müller, Ulrich UL; Philipp, Martine UL; Thomassey, Matthieu UL et al

in Thermochimica Acta (2013), 555

The volume expansion coefficient is a thermodynamic key parameter yielding insight into molecular cohesion and organization of condensed matter. We present here the novel experimental technique ... [more ▼]

The volume expansion coefficient is a thermodynamic key parameter yielding insight into molecular cohesion and organization of condensed matter. We present here the novel experimental technique temperature modulated optical refractometry (TMOR) to determine not only the static but also the dynamic volume expansion coefficient of transparent condensed matter of cubic or isotropic symmetry. A specialty of TMOR is its capability to measure the volume expansion coefficient under quasi-isothermal conditions. In this experimental mode TMOR is able to differentiate between static, dynamic and kinetic contributions to the volume expansion coefficient. Due to these features TMOR especially qualifies for the investigation of structural changes provoked by structural phase transitions, glass transitions and other structure-related transformations in transparent condensed matter. The scientific potential of this novel experimental technique is demonstrated by evidencing anomalies of the complex volume expansion coefficient accompanying the chemically induced glass transition occurring during the formation of a covalently cross-linked epoxy network. [less ▲]

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See detailCompetition Between Chemical Network Formation and Physical Adsorption and Desorption Processes in a Silica-Filled Silicone Rubber: Calorimetry versus Refractometry Studies
Krüger, Jan-Kristian UL; Müller, Ulrich UL; Zielinski, Bartosz UL et al

in Journal of Adhesion (2012), 88(7), 649-663

Calorimetry and high-performance refractometry are applied to study the network formation and accompanying morphological changes in reactive polydimethylsiloxane systems filled with silica nanoparticles ... [more ▼]

Calorimetry and high-performance refractometry are applied to study the network formation and accompanying morphological changes in reactive polydimethylsiloxane systems filled with silica nanoparticles. Both methods give insight into the structure formation during the polymerization of silica-filled silicone nanocomposites in an impressively complementary way. It will be shown that the specific heat flow as determined by calorimetry does not allow for estimating the chemical conversion whereas the refractive index does, which results from the different perspectives of both techniques on the relevant polymerization, adsorption, and desorption processes occurring in the nanocomposites. Finally, the interphase formation in the polymeric matrix in the vicinity of the nanoparticles and the network formation within the silicone rubber are demonstrated to be strongly correlated processes. [less ▲]

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See detailScanning Brillouin Microscopy: Acoustic Microscopy at Gigahertz Frequencies
Philipp, Martine UL; Müller, Ulrich UL; Sanctuary, Roland UL et al

in Archives des Sciences Naturelles, Physiques et Mathématiques (2012), NS 46(Special volume (invited Review Article)),

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See detailInfluence of Nanoparticles on the Coupling Between Optical Dipoles in Epoxy-Silica Nanocomposites During Network Formation
Philipp, Martine UL; Müller, Ulrich UL; Gervais, Pierre-Colin et al

in The Journal of Adhesion (2012), 88(7), 566-588

High-performance refractometry and infrared spectroscopy are combined in order to elucidate the gelation process and the glass transition during the network formation of epoxies and epoxy-based ... [more ▼]

High-performance refractometry and infrared spectroscopy are combined in order to elucidate the gelation process and the glass transition during the network formation of epoxies and epoxy-based nanocomposites. Whereas infrared spectroscopy yields the chemical conversion due to the opening of oxirane rings during the covalent network formation, high-performance refractometry is extremely sensitive to the accompanying changes of the arrangement of the molecular network. In accordance with the Lorentz-Lorenz relationship, the evolution of the refractive index seems to reflect that of the mass density during polymerization of the epoxy-based systems within the limits of a few percent. The slight deviations from the Lorentz-Lorenz relationship, which occur during the gelation of the epoxy-based systems, are attributed to long-ranged dipole-dipole interactions, which respond at optical frequencies. This point of view is supported by the fact that chemically inert silica nanoparticles embedded in the pure epoxy matrix as disturbances for these dipole-dipole interactions are able to diminish or even to suppress totally this excess contribution of the refractive index. [less ▲]

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See detailStructural properties of poly(N-isopropyl acrylamide)-based systems
Philipp, Martine UL; Magerl, D.; Aleksandrova, Ralitsa UL et al

Poster (2011, October 10)

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See detailStructural properties of poly(N-isopropyl acrylamide)-based systems
Philipp, Martine UL; Magerl, D.; Aleksandrova, Ralitza UL et al

Poster (2011, June 08)

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See detailStructural properties of poly(N-isopropyl acrylamide)-based systems
Philipp, Martine UL; Magerl, D.; Aleksandrova, Ralitsa UL et al

Poster (2011, June 01)

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See detailHeterogeneous Transport Processes and Unexpected Structure Formation in Layered Epoxy and Epoxy-Alumina Nanocomposite Systems
Philipp, Martine UL; Müller, Ulrich UL; Sanctuary, Roland UL et al

in Journal of Adhesion (2011), 87(11), 1073-1098

Static and dynamic hypersonic properties are probed to reveal the subtle interplay between demixing, matter transport, chemical network formation, polymer network swelling, and network damage in the ... [more ▼]

Static and dynamic hypersonic properties are probed to reveal the subtle interplay between demixing, matter transport, chemical network formation, polymer network swelling, and network damage in the vicinity of the interface between the reactants of amine-curing epoxies. An innovative time- and space-resolved acoustic microscopy, called scanning Brillouin microscopy, gives access to these competing transport and structure formation processes in epoxy systems consisting of either pure resin, alumina nanoparticles-filled resin, or various epoxy resin-hardener mixtures topped by a layer of pure hardener. Static and dynamic hypersonic properties are probed to reveal the subtle interplay between demixing, matter transport, chemical network formation, polymer network swelling, and network damage in the vicinity of the interface between the reactants of amine-curing epoxies. An innovative time- and space-resolved acoustic microscopy, called scanning Brillouin microscopy, gives access to these competing transport and structure formation processes in epoxy systems consisting of either pure resin, alumina nanoparticles-filled resin, or various epoxy resin-hardener mixtures topped by a layer of pure hardener. [less ▲]

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See detailOn the interplay between matter transport and structure formation at epoxy-hardener interfaces visualized by scanning Brillouin microscopy
Philipp, Martine UL; Müller, Ulrich UL; Sanctuary, Roland UL et al

in Soft Matter (2011), 7(1), 118-124

Structural developments are investigated in network-forming reactive polymers by time- and 10 space-resolved scanning Brillouin microscopy. Hypersonic properties are probed to reveal the subtle interplay ... [more ▼]

Structural developments are investigated in network-forming reactive polymers by time- and 10 space-resolved scanning Brillouin microscopy. Hypersonic properties are probed to reveal the subtle interplay between molecular transport, dissolution, polymerization and network defects in the vicinity of the interface between reactants, which are either pure epoxy resin or various epoxy resin-hardener mixtures, topped by a layer of pure hardener. The trans-interfacial polymerization produces heterogeneous epoxy structures of either gelatinous or glassy nature. Interestingly, the 15 hardener can easily penetrate and swell these networks and epoxy network fragments can be transported over several millimeters by convective flow. The observed features may be used to form interpenetrating networks during self-healing procedures. [less ▲]

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See detailCombination of high performance refractometry and infrared spectroscopy as a probe for chemically induced gelation and vitrification of epoxies
Müller, Ulrich UL; Philipp, Martine UL; Gervais, P. C. UL et al

in New Journal of Physics (2010), 12

A combination of infrared spectroscopy and high performance refractometry was used to investigate the chemically induced sol-gel and glass transition during the polymerization of epoxies. Representations ... [more ▼]

A combination of infrared spectroscopy and high performance refractometry was used to investigate the chemically induced sol-gel and glass transition during the polymerization of epoxies. Representations of the refractive index versus chemical conversion reveal an interesting insight in the optical properties accompanying gelation and vitrification. Whereas the electronic polarizability of the liquid state of small average molecular mass and the glassy state is dominated by the mass density, an unexpected excess polarizability observed during the gelation is attributed to cooperative dipole-dipole interactions. [less ▲]

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See detailTrans-Interfacial Polymerization and Matter Transport Processes in Epoxy-Alumina Nanocomposites Visualized By Scanning Brillouin Microscopy
Sanctuary, Roland UL; Philipp, Martine UL; Kieffer, J. et al

in Journal of Physical Chemistry B (2010), 114(25), 8396-8404

The structural developments in the vicinity of the interface between the reactants of an epoxy are investigated using time- and space-resolved scanning Brillouin microscopy. The hypersonic profile across ... [more ▼]

The structural developments in the vicinity of the interface between the reactants of an epoxy are investigated using time- and space-resolved scanning Brillouin microscopy. The hypersonic profile across the phase boundary evolves with strong spatial asymmetry and exhibits erratic behavior within the resin-rich region, which is attributed to a complex interplay between matter transport, dissolution, polymerization, and molecular unravelling process. The presence of alumina nanoparticles in the resin changes the character of these matter transport and reaction processes significantly. On the one hand, the nanoparticles act as transport barriers, hindering the mixing of the reactive components; on the other hand they seem to have a catalytic influence on the epoxy polymerization under certain circumstances. Their transport against gravity is tentatively attributed to gradients in surface tension. [less ▲]

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See detailNichtgleichgewichtsphänomene, Strukturbildung und Grenzflächeneinflüsse in netzwerkbildenden Systemen aus optischer und akustischer Sicht.
Philipp, Martine UL

Doctoral thesis (2009)

Isostructural phase transitions occurring under non-equilibrium conditions are investigated using technologically relevant epoxies. The evolution of the hypersonic and optical properties during the ... [more ▼]

Isostructural phase transitions occurring under non-equilibrium conditions are investigated using technologically relevant epoxies. The evolution of the hypersonic and optical properties during the genesis of the polymeric network leads to deeper insight into the chemically induced sol-gel transition and glass transition, as demonstrated e.g. by the elastic anharmonicity and the generalised Cauchy relation. During gelation the refractive index versus chemical conversion behaves in an unexpected manner, indicating that in addition to the mass density an excess polarisability seems to contribute to the optical polarisability. The clarification of the isostructural phase transitions is impeded by the demixing tendency of the epoxy components which leads to different types of epoxy inhomogeneities on the nano- to mesoscopic scale. Taking benefit from a sample arrangement where both epoxy components are layered, the spatio-temporal evolution of acoustic properties gives supplementary information about trans-interfacial transport and structure formation processes. Of special technological relevance, but also of fundamental interest, is the influence of nanoscopic disturbances placed into the epoxy matrix. So-called interphases surrounding the nanoparticles modify and complicate the epoxy network formation, leading to long-lived metastable morphologies and properties. The role of the mixing sequence of the epoxy resin, the hardener and the nanoparticles for the polymerised epoxy state and the transient states during network formation, as well as the isostructural phase transitions is further elucidated. [less ▲]

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See detailMixing Behavior and Interphase Formation in the Diethylene Triamine-Water System Studied by Optical Imaging and Spatially Resolved Brillouin Scattering
Philipp, Martine UL; Collette, Florimond; Veith, Michael et al

in Journal of Physical Chemistry B (2009), 113(38), 12655-12662

The injection of water beneath liquid diethylene triamine in a glass cuvette leads to an unexpected phase evolution behavior of the two liquids. The space and time dependent developments of the molecular ... [more ▼]

The injection of water beneath liquid diethylene triamine in a glass cuvette leads to an unexpected phase evolution behavior of the two liquids. The space and time dependent developments of the molecular structure and the underlying transport associated with mixing of the two liquids are monitored by optical imaging and scanning Brillouin microscopy. Apparently, results obtained by either experimental technique lead to disparate interpretations. Whereas optical imaging suggests the existence of a two phase structure, which disappears within a few hours, acoustic microscopy indicates the evolution of a more gradually evolving and longer-lived three phase structure. According to molecular acoustics, the transport of diethylene triamine into water and vice versa behaves strongly asymmetric in time. An attempt is made to reconcile the observed optical and acoustic manifestations of the mixing process on the basis of molecular complex formation. [less ▲]

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