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Herein, we report a simple and versatile synthetic approach towards siloxane‐based poly(ionic liquid)s (PILs) with unusually low glass transition temperatures (Tg) down to −73°C, and thus “liquid‐like” behavior at room temperature. We designed a polydimethylsiloxane‐derived copolymer carrying dialkylimidazolium moieties, and by careful selection of the side‐chain length and the type of anions we were able to manipulate its Tgover a wide range and reach high ionic conductivities (σDC) up to 4.8 × 10−5S/cm at 300 K. The ionized species make up only a minor fraction (<25 mol%) of the overall repeating units and are supposedly randomly distributed: Yet our results indicate dramatic effects on the thermal properties due to repulsive interactions between ionic and non‐ionic segments.

Spider silks are remarkable materials designed by nature to have extraordinary elasticity. Their elasticity, however, remains poorly understood, as typical stress–strain experiments only allow access to the axial Young’s modulus. In this work, micro-Brillouin light spectroscopy (micro-BLS), a noncontact, nondestructive technique, is utilized to probe the direction-dependent phonon propagation in the Nephila pilipesspider silk and hence solve its full elasticity. To the best of our knowledge, this is the first demonstration on the determination of the anisotropic Young’s moduli, shear moduli, and Poisson’s ratios of a single spider fiber. The axial and lateral Young’s moduli are found to be 20.9 ± 0.8 and 9.2 ± 0.3 GPa, respectively, and the anisotropy of the Young’s moduli further increases upon stretching. In contrast, the shear moduli and Poisson’s ratios exhibit very weak anisotropy and are robust to stretching.

Polyimides are interesting polymer materials for organic solvent nanofiltration (OSN) applications because of their high excess free volume and high chemical and temperature resistance. However, an open challenge that remains for glassy polymer materials (i.e., polyimides) is their tendency to swell in organic solvents which can lead to a loss of performance. An understanding on how swelling influences the polymer properties and performance is then of crucial importance for assessing polyimide suitability in OSN applications. Here, the combination of in situ spectroscopic ellipsometry (iSE), broadband dielectric spectroscopy (BDS), and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT-FTIR) is applied to study the molecular interaction of two organic penetrants, toluene and n-hexane, with Matrimid 5218 in detail. iSE shows that slightly cross-linked Matrimid 5218 swells approximately seven times more in toluene (swelling degree ≈ 28%) compared to in n-hexane (swelling degree ≈ 4%). Combined BDS and DRIFT-FTIR results indicate that toluene interacts with the benzene ring present in the diamine via π–π interactions, while n-hexane likely fills up the excess free volume and interacts via local van der Waals interactions. This work highlights the insights into the exact nature of the molecular interactions between the penetrant and polymer that can be gained from a combination of BDS and other techniques and how these insights can be used to estimate or understand solvent-induced swelling of polymers used in OSN applications.

Broadband dielectric spectroscopy (BDS) and orthopositronium annihilation lifetime spectroscopy (PALS) are combined to study the molecular dynamics and the free volume of poly(propylene glycol) terminated with amino end groups (PPG-NH2) in the bulk state and when confined in native and silanized unidirectional silica nanopores with average diameters of 4, 6, and 8 nm. In the bulk state, three dielectric relaxation processes are observed: (i) the fast β-relaxation assigned to the librational fluctuations of the −O–NH2moiety, (ii) the α-process corresponding to the dynamic glass transition, and (iii) the (slower) chain dynamics or normal mode (NM) relaxation. Under confinement in native nanopores, the β-process becomes slower, while the α and the normal mode relaxation processes become faster and broader and demonstrate a lower dielectric strength with decreasing pore diameter. In silanized nanopores the normal and β-processes are nearly bulklike, but the α-process still remains faster than bulk closer to the Tg. All these findings can be comprehended as controlled by the counterbalance between surface and confinement effects. The former are caused by attractive interactions with the solid walls of the nanopores (resulting in an additional slower process which is removed after silanization), and the latter are caused by an increase of the free volumeof the polymer segments due to a less efficient packing as proven by orthopositronium annihilation lifetime spectroscopy. These results conform to the cooperative free volume model (CFV).

Spider dragline silk possesses superior mechanical properties compared with synthetic polymers with similar chemical structure due to its hierarchical structure comprised of partially crystalline oriented nanofibrils. To date, silk’s dynamic mechanical properties have been largely unexplored. Here we report an indirect hypersonic phononic bandgap and an anomalous dispersion of the acoustic-like branch from inelastic (Brillouin) light scattering experiments under varying applied elastic strains. We show the mechanical nonlinearity of the silk structure generates a unique region of negative group velocity, that together with the global (mechanical) anisotropy provides novel symmetry conditions for gap formation. The phononic bandgap and dispersion show strong nonlinear strain-dependent behaviour. Exploiting material nonlinearity along with tailored structural anisotropy could be a new design paradigm to access new types of dynamic behaviour.

The impact of 1- and 2-dimensional (2D) confinement on the structure and dynamics of poly(styrene-b-1,4-isoprene) P(S-b-I) diblock copolymer is investigated by a combination of Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Grazing-Incidence Small-Angle X-ray Scattering (GISAXS), and Broadband Dielectric Spectroscopy (BDS). 1D confinement is achieved by spin coating the P(S-b-I) to form nanometric thin films on silicon substrates, while in the 2D confinement, the copolymer is infiltrated into cylindrical anodized aluminum oxide (AAO) nanopores. After dissolving the AAO matrix having mean pore diameter of 150 nm, the SEM images of the exposed P(S-b-I) show straight nanorods. For the thin films, GISAXS and AFM reveal hexagonally packed cylinders of PS in a PI matrix. Three dielectrically active relaxation modes assigned to the two segmental modes of the styrene and isoprene blocks and the normal mode of the latter are studied selectively by BDS. The dynamic glass transition, related to the segmental modes of the styrene and isoprene blocks, is independent of the dimensionality and the finite sizes (down to 18 nm) of confinement, but the normal mode is influenced by both factors with 2D geometrical constraints exerting greater impact. This reflects the considerable difference in the length scales on which the two kinds of fluctuations take place.

We present a novel experimental approach for determining the dynamics of free-standing ferroelectric liquid crystalline films in the frequency range from 1 Hz to 103Hz. By measuring the dynamic infrared dichroism of specific absorption bands in a free-standing FLC-film exposed to rotating external electric fields within a miniaturized electrode arrangement the collective dynamics and the innermolecular response of the FLC system can be analysed. In the SmC* phase a dynamic process is found which corresponds to a resonant switching behaviour which can be described by the model of kink switching. The main contribution to the dynamics of the SmC* phase is caused by the molecular moieties in the mesogenic core.

Optical tweezers-assisted dynamic force spectroscopy is employed to investigate specific receptor–ligand interactions on the level of single binding events. In particular, we analyze binding of the phosphorylation-specific monoclonal antibody (mAb) HPT-101 to synthetic tau-peptides with two potential phosphorylation sites (Thr231 and Ser235), being the most probable markers for Alzheimer’s disease. Whereas the typical interpretation of enzyme-linked immunosorbent assay (ELISA) suggests that this monoclonal antibody binds exclusively to the double-phosphorylated tau-peptide, we show here by DFS that the specificity of only mAb HPT-101 is apparent. In fact, binding occurs also to each sort of monophosphorylated peptide. Therefore, we characterize the unbinding process by analyzing the measured rupture force distributions, from which the lifetime of the bond without force τ0, its characteristic length xts, and the free energy of activation ΔGare extracted for the three mAb/peptide combinations. This information is used to build a simple theoretical model to predict features of the unbinding process for the double-phosphorylated peptide purely based on data on the monophosphorylated ones. Finally, we introduce a method to combine binding and unbinding measurements to estimate the relative affinity of the bonds. The values obtained for this quantity are in accordance with ELISA, showing how DFS can offer important insights about the dynamic binding process that are not accessible with this common and widespread assay.

Infrared Transition Moment Orientational Analysis (IR–TMOA) and Broadband Dielectric Spectroscopy (BDS) are combined to study molecular order and dynamics of the glass-forming liquid Tris(2-ethylhexy)phosphate (TEHP) confined in uni-directional nanopores with diameters of 4, 8, and 10.4 nm. The former method enables one to determine the molecular order parameter of specific IR transition moments. It is observed that the central P=O moiety of TEHP has a weak orientational effect (molecular order parameter Sz= −0.1± 0.04) due the nanoporous confinement, in contrast to the terminal C–H groups. BDS traces the dynamic glass transition of the guest molecules in a broad spectral range and at widely varying temperature. An enhancement of the mobility takes place when approaching the glass transition temperature and becomes more pronounced with decreasing pore diameter. This is attributed to a slight reduction of the density of the confined liquid caused by the 2-dimensional geometrical constraint.

Forces of interaction within singlepairs of negatively charged microsized blank colloids in aqueous solutions of water miscible room temperature ionic liquids (RTILs) have been measured at varying concentrations and pH by using optical tweezers (OT). Three different water miscible RTILs (1-butyl-3-methylimidazolium tetrafluoroborate [BMIM-BF4], 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM-TfO], and 1-butyl-3-methylimidazolium chloride [BMIM-Cl]) having the same organic cation [BMIM]+and different inorganic anions ([BF4]−, [TfO]−, and Cl−) are used and compared with the high temperature molten salt (KCl). The experimental data are well described by a size-corrected screened Coulomb interaction approach which originates from the linearized Poisson−Boltzmann (PB) equation. The effective surface charge density σ derived from the fitted force-separation data is found to be concentration and pH dependent.

Minor and major ampullate spider silks are studied under varying mechanical stress by static and time‐resolved FT‐IR spectroscopy. This enables one to trace the external mechanical excitation on a microscopic level and to determine for the different moieties the time dependence of the molecular order parameters and corresponding band shifts. It is concluded that the hierarchical nanostructure of both types of silk is similar, being composed of highly oriented nanocrystals, which are interconnected by amorphous chains that obey the worm‐like chain model and have a Gaussian distribution of pre‐strain. By that it is possible to describe the mechanical properties of both silks by two adjustable parameters only, the center and width of the distribution. For major ampullate silk, the observed variability is small in pronounced contrast to the findings for minor ampullate.

Composites of PUR and IL were prepared and specific conductivities and Shore A hardness were determined. IL were based on 1-alkyl3methylimidazolium salts with counterions BF4−, PF6−, triflate, or ethylsulfate. Presence of IL increased the conductivity by five orders of magnitude. Variation of alkyl chain length and nature of counterions only had little effect on the conductivity. Presence of IL had a plasticizing effect, which was most pronounced for the IL with dodecyl groups and PF6−as counterion. In broadband dielectric measurements, the complex conductivity showed a characteristic dispersion that is caused by the interplay between hopping transport of charge carriers and electrode polarization.

The impact of the preparation and thermal history on the dynamic glass transition in thin films of polymethyl methacrylate and polyvinyl acetate is systematically investigated by means of broadband dielectric spectroscopy. Metastable states of glassy dynamics are detected, exhibiting shifts in the meanrelaxation time from the bulk values. These shifts possibly mimicking confinementeffects in thin polymer films become weaker or even disappear after an extensive annealing.

Abstract: A series of alternating maleimide (MI) copolymers with fluorinated side chains have been investigated using broadband dielectric spectroscopy. The side chains consist of fluoroalkane (–C x F2x+1, x=1, 7, 9) end groups connected to the main chain via methylene spacers. The experiments were carried out in a frequency range of 0.1 Hz to 10 MHz and at temperatures between 120 K and 500 K. The fluorinated MI copolymers show a fast sub-T g (β) relaxation characterized by an Arrhenius-type temperature dependence with activation energy in the range of 30–37 kJ/mol. Two more processes (α and δ-like) are observed, corresponding to independent relaxations of the main chain and the fluoroalkane domains respectively. For shorter side chains, the δ-like process is not observed but instead another relaxation process, α S , occurs at temperatures higher than either the α and δ-like processes. When compared with unfluorinated MI copolymers, the fluorinated MI copolymers show the δ-like process and a slower β-relaxation unlike their unfluorinated counterparts. A model to explain the molecular origin of the four processes is proposed, supplemented by differential scanning calorimetry and published WAXS/SAXS data.

Summary: Two sets of side-chain, liquid-crystalline ionomers based on copolymers of butyl acrylate and 4-{[6‐(acryloyloxy)hexyl]oxy}benzoic acid containing 2.5–20 mol‐% of lithium or rubidium ions were studied. As the content of ions of alkali metals increases, segmental mobility markedly decreases. As compared with rubidium‐containing ionomers, ionomers containing lithium ions are characterized by a far more efficient decrease in their dielectric relaxation times because ionic radius of lithium ions is lower than that of rubidium ions.

Summary: Fourier transform infrared (FTIR) spectroscopy with polarized light is employed to study the segmental orientation and the order of a nematic liquid crystalline elastomers (NLCEs) with a monodomain structure in response to an external mechanical field. The reorientation and the order parameter of the different molecular moieties are analyzed in detail, revealing information about angular excursion in the rearrangement of the mesogens, the spacer molecules, and the main-chain. In case of an elongation of the NLCE films perpendicular to the initial mesogen orientation, no reorientation or change of order is observed for an elongation ratio less than 1.3. At higher strain, a molecular reorientation process is induced on all molecular segments and the order of alignment is decreased. When the NLCE-films are stretched parallel to the mesogens, no molecular reorientation takes place and the order parameters show no significant change.Angular reorientation of different molecular moieties at mechanical strain perpendicular to the initial mesogen orientation.

Herkömmliche Hochleistungs‐Piezomaterialien erreichen bei Anlegen elektrischer Spannung einen Hub von maximal 0, 1 % ihrer Längen. Arbeitsgruppen der Universtäten Leipzig und Mainz haben ein neues, ferroelektrisches Elastomer entwickelt, das auf Flüssigkristallen basiert. Die Flüssigkristallmoleküle sind so in das Polymernetzwerk eingebunden, dass sie sich wie mikroskopische Hebel bewegen und Kräfte übertragen können. Bei einem elektrischen Feld von nur 1, 5 kV/mm ändert ein frei tragender Film des neuen Materials seine Dicke um bis zu 4 %. Das ist Weltrekord und eröffnet völlig neue Felder für technische Anwendungen.

We report the electric field induced thickness variations of homeotropically oriented free standing films of a smectic (C* or A*) FLCE prepared from cross - linkable ferroelectric polysiloxanes. The changes in optical path length in free standing ferroelectric liquid crystal elastomer films have been detected by means of interferometric measurements at both the first and second harmonic of the exciting electric field (ω=33 Hz). The measured electrostrictive strain is above 2.7% (in the thickness direction) at a electric field around 1.5 MV /m. Our experiment reveal that the inverse piezoelectric and electrostrictive response increases sharply near the Sm-C* - Sm-A* phase transition temperature. Also X-ray reflection measurements on a spin cast FLCE film reveal the constriction of smectic layers.

The synthesis of poly(vinyl ether)s or polyvinylcarbazole under the conditions of constricted geometry can be achieved by means of cationic host–guest polymerisation of the corresponding monomers in the pores of MCM‐41 (pore diameter 3.6 nm), MCM‐48 (pore diameter 2.4 nm) and in nanoporous glasses (Gelsil®with a pore diameter of 5 nm) with bis(4‐methoxyphenyl)methyl chloride (BMCC) or triphenylmethyl chloride as the internal surface initiator. The reaction products are new polymer/MCM‐41, polymer/MCM‐48 etc., host–guest hybrid materials. The molecular mass of the enclosed polymer and the degree of loading of the host compounds can be adjusted within certain limits. The molecular dynamics were investigated by using broad‐band dielectric spectroscopy. Under the conditions of constricted geometry, molecular fluctuation is observed as well as a secondary β‐relaxation, which is hardly affected (in comparison with the free melt) and which corresponds to the relaxation between structural substates (dynamic glass transition). This process is several orders of magnitude faster in its relaxation rate than in the free melt and thus follows a confinement effect. This is already well known in lower molecular weight systems with constricted geometry.

AbstractThe molecular structure and reorientation of ferroelectric liquid crystalline elastomers (FLCE) in response to an external electric field is studied on a microsecond scale with time-resolved Fourier transform infrared (FTIR) spectroscopy. In order to analyze the influence of the network on the molecular structure and mobility in FLCE, three similar FLC polysiloxanes are under study that differ just in their crosslinking architecture: besides the uncrosslinked polymer we obtain by photocrosslinking FLCE in which the backbones of either adjacent smectic layers (“interlayer”) or of the same smectic layer (“intralayer”) are preferably crosslinked. It is shown that the crosslinking leads to a slowing down of the molecular mobility which is stronger for the inter-than for the intralayer FLCE. Asymmetries in the reorientation times and/or in the reorientation angles are observed (elastic memory effect). The intralayer crosslinking causes a “locomotive effect”: the reorientation of the mesogenic cores precedes that ofthe backbones.

A hydrogen-bonded blend based on comb-shaped functionalized LC copolymers containing alkyloxy-4-hydroxybenzoic acid fragments (proton donor) and a low molecular weight dopant 4-(4-pyridyloyl)methoxybenzoate-d4 (proton acceptor) was obtained. The temperature dependence of the order parameter S, the birefringence Δn and the bend elastic constant K3 of the LC copolymer and blend were studied by the ²H NMR spectroscopy and the Freedericksz method of threshold transitions in a magnetic field. The formation of the blend leads to a decrease of the order parameter S of the functionalized LC copolymer. The essential difference in the order parameter S of the mesogenic groups of the LC copolymers and the dopant molecules was established.

A number of new functionalized LC copolymers containing mesogenic oxycyanobiphenyl groups and 3–41 mol-% of maleic acid has been obtained by free-radical copolymerization in solution. A significant effect of intramolecular hydrogen bonds on the phase behavior of these copolymers is observed: for a maleic acid content of up to 8 mol-% LC copolymers form only the nematic and between 10–41 mol-% the SmA phase is formed. The process of formation of anhydrides in functionalized LC polymers at 130°C is investigated. It is shown that the formation of five-membered intramolecular anhydride rings does not influence the phase behavior of the LC polymers.

A novel technique to contact (ultra‐) thin polymer layers is presented which enables to compare the molecular dynamics in grafted films of poly(γ‐benzyl‐L‐glutamate) (PBLG) to that of the bulk polymer by means of dielectric spectroscopy. Two relaxation processes are observed which are assigned to restricted fluctuations of the helical main chains and to the dynamic glass transition of the side chains. Furthermore, the swelling behavior of PBLG is studied.

The electrically induced thickness variations of homeotropically oriented free standing films of a smectic (C* and A*) ferroelectric liquid crystalline elastomer (FLCE) have been examined. For this purpose an interferometric setup has been built with a resolution of 3 pm at 133 Hz AC excitation frequency. The laser beam has been focussed by means of two “long distance” microscope objective lenses in order to study small homogeneous areas in the film. The changes in optical pathlength through the sample were measured at the first (ω), second (2ω) and fourth (4ω) harmonic of the AC-electric excitation voltage (ω=133 Hz). The measured thickness (optical pathlength) modulation at the 2nd harmonic is in the range of some % and thus stronger than expected from FTIR-measurements on the electroclinic effect in CaF2 cells filled with this sample. Nevertheless, the strength of this quadratic effect and also of the linear effect is greatly increased at the phase transition Sm-C*-Sm-A*, which indicates a correlation of the thickness variation with the electroclinic effect.

To analyze the impact of the molecular structure on the network formation in ferroelectric liquid crystalline polymers, two copolymers are studied, which are identical except for the molecular position of the cross-linkable group: (i) Polymer P1 with cross-linkable groups attached to the backbone via a short spacer and (ii) Polymer P2 with the cross-linkable group in terminal position of a mesogenic side group. When mechanical stress is imposed on thin films in homeotropic orientation through stretching, the two elastomers react differently to the deformation, as seen by AFM imaging of the surface topology: For Polymer P1, “intra-layer” cross-linking results in two dimensional networks in each backbone layer, separated by liquid-like FLC sidegroup layers. As there are practically no vertical connections in this intralayer network, no vertical distortions occur. In Polymer P2 a three dimensional, “inter-layer” network is formed; the system reacts with a distortion of the smectic layering.

AbstractMicrotomized sections of single-crystalline ferroelectric liquid crystalline elastomers (SC-FLCE) have been prepared. The piezoelectric (and electrostrictive) responses in these sections have been measured by means of an interferometric setup and the pyroeletric properties have been determined using the laser intensity modulation method (LIMM).

Pulsed field gradient NMR and dielectric spectroscopy are applied to investigate the rates of molecular reorientation and translation of the glass-forming liquids propanediol and salol in porous glasses. Though there is a general tendency for the confinement in the pore system to reduce both the rotational and translational mobility in comparison with the liquid phase, in particular cases also an enhancement of the molecular mobility is observed. As a possible explanation of this enhancement it is assumed that the spatial confinement within the pore system excludes the formation of long-range molecular aggregates which dominate molecular dynamics in the bulk liquid.

Hydrogen‐bonded blends based on smectic comb‐shaped functionalized LC copolymers containing alkyloxy‐4‐hydroxybenzoic acid fragments (proton donor) and the low molecular weight dopant 4‐(4‐pyridyloyl)cyanobenzoate (proton acceptor) were obtained. It was observed that blends containing 10–25 mol‐% of low molecular weight dopants form a reentrant nematic phase (SmA‐RN‐SmA‐I). The blend behavior in the magnetic field was studied, and the orientational elastic constants of the RN phase were determined.

An ultra-stable Michelson interferometer is described which enables to measure periodic displacements (of a mirror in one interferometer arm) with a resolution of less than 100 fm. This setup is employed to measure the (linear) inverse piezoelectric and the (quadratic) electrostrictive effect in macroscopically oriented ferroelectric liquid crystalline elastomers (FLCE). A pronounced temperature dependence of the electromechanical effects is observed. Superposition of a DC-bias field leads to a strong enhancement of the inverse piezoelectric effect being well comparable in its strength with classical piezoceramics (BaTiO3, PZT, etc.). The molecular mechanisms of the observed effects are discussed.

This report is concerned with the use of guided optical waves for investigating ferroelectric liquid crystals, especially the electroclinic motion in the SmA phase and the switching motion in the SmC* phase. The optical waves are able to probe the molecular orientation and movement of the liquid crystal molecules under alternating electric fields.

Both a conservative rapid‐scan FT‐IR technique and a novel step‐scan FT‐IR technique with 2D correlation analysis were used to study the orientation and the mobility of a ferroelectric liquid crystal dimer during switching under an electric field. The detailed mutual arrangements of different molecular segments (mesogen, poly(methylene) chain, polysiloxane chain) in a smectic C* phase were derived from the static spectra. It was shown that the long mesogen axis, the average poly(methylene) and the average polysiloxane chain axes do not coincide with each other. The hindered rotation of the carbonyl group is confirmed. Time‐resolved FT‐IR technique was used to follow the segmental motion with a time resolution of 5 μs. The temperature and electric field strength dependencies of the mobility of these segments are discussed. 2D correlation analysis of time‐resolved data reveals small differences in the behavior of the carbonyl and the benzoic rings in the mesogen moieties, that can be explained as differences in the orientation distribution functions of these moieties.

AbstractIn recent years a substantial amount of research has been devoted under - standing of anchoring and ordering mechanisms of liquid crystal molecules near solid surfaces. The interaction of a liquid crystalline compound with a solid surface depends on the nature of both the surface and liquid crystal material. The dielectric measurements in untreated Anopore membranes confirm the planar axial order of nematic molecules; in membranes treated by decanoic acid, a polar-radial or polar - polar orientation of the molecules is very likely, although a slight escaped director structure at least at low temperatures seems to be indicated in the dielectric data.