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So far, it has been difficult to directly compare diverse characteristic gelation mechanisms over different length and time scales. This paper presents a universal water structure analysis of several gels with different structures and gelation mechanisms including polymer gels, supramolecular gels composed of surfactant micelles, and cement gels. The spatial distribution of water molecules was analyzed at molecular level from a diagram of the relaxation times and their distribution parameters (τ–β diagrams) with our database of the 10 GHz process for a variety of aqueous systems. Polymer gels with volume phase transition showed a small decrease in the fractal dimension of the hydrogen bond network (HBN) with gelation. In supramolecular gels with rod micelle precursor with amphipathic molecules, both the elongation of the micelles and their cross-linking caused a reduction in the fractal dimension. Such a reduction was also found in cement gels. These results suggest that the HBN inevitably breaks at each length scale with relative increase in steric hindrance due to cross-linking, resulting in the fragmentation of collective structures of water molecules. The universal analysis using τ–β diagrams presented here has broad applicability as a method to characterize diverse gel structures and evaluate gelation processes.

In this study, we investigated the cooperative molecular dynamics of poly(vinylpyrrolidone) (PVP), ice, and uncrystallized water (UCW) in partially crystallized PVP-water mixtures by means of broadband dielectric spectroscopy. Three relaxation processes, denoted I, II, and III, were observed at temperatures ranging from immediately below the crystallization temperature (Tc) to approximately 200 K. At temperatures of 173-193 K, processes I and II cannot be distinguished. Below 168 K, process II separates into two processes: process IV at higher frequencies and process V at lower frequencies. Process I contributes to process V. In partially crystallized mixtures, process I originates from UCW in an uncrystallized phase with PVP. Process II is attributed to ice in the mixture, with a relaxation time that is 2 orders of magnitude smaller than that of pure ice. The concentration dependence of the strength of process II and the relaxation time relative to that of ice in bovine serum albumin (BSA)-water and gelatin-water mixtures strongly support this conclusion. Observation of processes IV and V indicates the presence of multiple ice relaxation processes. Process III is attributed to the α process of PVP in the uncrystallized phase in 40 and 50 wt % PVP mixtures. For mixtures with 30 wt % PVP or less, process III is attributed not only to the α process of PVP but also to interfacial polarization.

To investigate the dielectric relaxations of ice in low-concentration protein-water mixtures, broadband dielectric spectroscopy measurements were performed on partially crystallized bovine serum albumin (BSA)-water mixtures with BSA concentrations of 1-10 wt% at temperatures in the range of 123-298 K. The temperature dependence of the relaxation time of ice observed in all these mixtures changes twice at

Analytical technique using the τ−β diagram offers variations to evaluate aqueous complex systems. Those recent applications of the fractal analysis offer us simple and clear understanding of water structures as one of most effective tools for moist materials including living tissues. The newer application studies are summarized as follows; 1. Only a single plot: comparison with our database, 2. Structured water: such as water in cement materials, 3. Ion migrations: Maxwell-Wagner effect, 4. Stability of materials including homeostasis for biological tissues. As the skin condition recovers over a longer period after coating glycerol aqueous solutions, the τ−β diagram indicated more typical hyperbolic behavior for plots obtained at 60 minutes after coating. This result indicates that the fractal analysis can be used for evaluations of homeostasis.

In recent years, there is a massive demand for the development of high-performance sensing technologies to curtail the effect of environmental pollutions. One such primary ecological concern is water pollution, where the major risk factor is associated with the concentrations of the chemical residues (hydrogen peroxide [H2O2]) in drinking water. Keeping this in view, we have demonstrated a non-enzymatic electrochemical probing of H2O2 in water employing microwave-assisted TiO2-ZrO2-HfO2 ternary nanocomposite for the first time. Structural analysis revealed the formation of monoclinic phases of ZrO2 and HfO2 along with anatase phased TiO2. Dynamic sensing characteristics of the TiO2-ZrO2-HfO2 nanocomposite were studied by varying the concentration of H2O2 from 1 to 19 µM where the sensor showed linearity up to 9 µM. The LOD and LOQ of the sensor were found to be 0.32 and 1.06 µM respectively along with the sensitivity of 6.71 $$\mu \mathrm{A}\bullet\upmu {\mathrm{M}}^{-1}$$ . The dominant signal change of Zr4+ ions in the TiO2-ZrO2-HfO2 nanointerface upon interacting with H2O2 has significantly inhibited the Hf4+ ions from taking part in the redox reaction, which refers to the sacrificial behavior. The reaction hierarchy was observed as ZrO2 (Eo = − 1.23 V) > TiO2 (Eo = − 1.15 V [suppressed peak]) > HfO2 (no redox peaks observed sacrificial). The real-time recovery study was carried out using the tap water, field water, and urban river water samples with repeatable and reproducible characteristics. Thus, our study provokes a new dimension in exploring many ternary nanointerfaces in the near future for the electrochemical sensing of different analytes.

The effect of hydrophobicity on thermal diffusion of acetylated dextran in aqueous solution was studied in the temperature range of 15–50 °C by optical beam deflection (OBD) technique. The hydrophobicity was controlled by substitution of hydroxyl groups on dextran chain with acetylated groups. The Soret coefficient ST and thermal diffusion coefficient DT significantly increased with an increase of temperature. The hydrophobicity plays an important role in the thermal diffusion behavior, i.e. ST and DT switch the sign from negative to positive magnitude with an increase of hydrophobic contents. We observed a correlation between the parameters obtained from Iacopini and Piazza equation (Europhy. Lett. 63 (2003) 247–253.) and the hydrophobic content of the binary aqueous solutions. A master curve can be used to describe the temperature dependence of ST and DT for acetylated samples. The ST linearly decreases with an increase of particle size for dextran whereas it scales linearly with the volume of particles for acetylated samples.

A novel polymer host from carboxymethyl cellulose (CMC)/poly(N-isopropylacrylamide) (PNiPAM) was developed for a high safety solid polymer electrolyte (SPE) in a zinc ion battery. Effects of the PNiPAM loading level in the range of 0–40% by weight ( wt%) on the chemical, mechanical, thermal, and morphological properties of the CMC/PNiPAMx films (where x is the wt% of PNiPAM) were symmetrically investigated. The obtained CMC/PNiPAMx films showed a high compatibility between the polymers. The CMC/PNiPAM20 blend showed the greatest tensile strength and modulus at 37.9 MPa and 2.1 GPa, respectively. Moreover, the thermal degradation of CMC was retarded by the addition of PNiPAM. Scanning electron microscopy images of CMC/PNiPAM20 revealed a porous structure that likely supported Zn2+ movement in the SPEs containing zinc triflate, resulting in the high Zn2+ ion transference number (0.56) and ionic conductivity (1.68 × 10–4 S cm−1). Interestingly, the presence of PNiPAM in the CMC/PNiPAMx blends showed a greater stability during charge–discharge cyclic tests, indicating the ability of PNiPAM to suppress dendrite formation from causing a short circuit. The developed CMC/PNiPAM20 based SPE is a promising material for high ionic conductivity and stability in a Zn ion battery.

This study investigates the cooperative molecular dynamics of poly(vinyl methyl ether) (PVME) at temperatures above and below the glass transition temperature, Tg, using differential scanning calor...

The dynamic behavior of water molecules in tofu gels is observed using dielectric spectroscopy (DS) and pulsed field gradient nuclear magnetic resonance (PFG-NMR) methods. The breaking stress of tofu gels are dependent on the heating time, which affects the water structures characterized by the dielectric relaxation time, τ. On the other hand, the inhomogeneity of the gel structures decreases with increasing coagulant concentration was reflected as decreasing of the dielectric broadening parameter, β, that related for a fluctuation of the dynamic water structure. In addition, a decrease in the translational diffusion coefficient of water molecules is obtained with increasing coagulant concentration suggesting a reduction of the free space for the diffusional motion of water molecules. Negative correlations between the broadening parameter, β, and the inverse of diffusion coefficient, 1/D, are found in tofu gels and soymilk with distinct correlation coefficients of −0.95 and −0.87, respectively. These results suggest that water dynamics analysis and complementary analysis using DS and PFG-NMR measuring techniques can be an effective tool to evaluate food gel physical properties. Further these technique could also explain the molecular mechanisms of gel and liquid structures and properties via dynamic water structures.

The dielectric relaxation process of water has been investigated for a partially crystallized poly(ethylene glycol) (PEG)–water mixture with PEG concentrations of up to 50 wt% at temperatures between −60 and 25 °C and over the frequency range of 1 MHz to 50 GHz. At subzero temperatures, most of the water is crystallized, and another portion of the water, uncrystallized water (UCW), remains in a liquid state with the polymer in an uncrystallized phase. The relaxation strength, Δɛ, of UCW for all PEG–water mixtures increased abruptly because of the melting of the eutectic of PEG and water. The Δɛ of UCW for 10–40 wt% PEG–water mixtures increased again because of the melting of ice, whereas the 50 wt% PEG–water mixture did not show any additional increase in Δɛ because it did not contain enough water to form ice crystals. The relaxation time of UCW in PEG–water mixtures is smaller than those observed in other polymer–water mixtures. The local fluctuation of the PEG chain, which has a smaller relaxation time than those of other polymers in water mixtures, and the characteristic hydration structure around the PEG chain prevent the formation of ice crystals even for water with a small relaxation time. The dielectric relaxation process of uncrystallized water (UCW) has been investigated for poly(ethylene glycol) (PEG)–water mixtures. The relaxation strength, Δɛ, of UCW for all PEG–water mixtures increased because of melting of the eutectic. For 10–40 wt% PEG–water mixtures, Δɛ increased again because of the melting of ice, whereas 50wt % PEG–water mixture did not show any additional increase because it did not contain enough water to form ice crystals.

Self-assembly of acetylated dextran (Ac-DEXs) was investigated with a modified dextran with acetic anhydride in the presence of pyridine. The effect of acetylation degree on solution properties has been investigated by static and dynamic light scattering (DLS). Molecular weight (Mw) and the radius of gyration (Rg) of dextran significantly increased with acetylation degree due to the aggregates formation. However, those aggregates noticeably reduced with further increase of acetylation degree. It suggested that the aggregates have shrinkage. The aggregate formation is clearly confirmed by DLS analysis in the presence of the bimodal relaxation distribution for Ac-DEXs. The hydrodynamic radius (Rh) of fast and slow mode is distinctly corresponded with single dextran macromolecules and aggregates, respectively. The Rh of aggregates varied slightly with increasing acetylation degree. The aggregates of Ac-DEXs represent hard spherical nanoparticles whereas the random coil structure is found in dextran. Formation of gel nanoparticles was monitored at the highest acetylated substitution.

Natural polysaccharides represent a renewable resource whose effective utilization is of increasing importance. Chemical modification is a powerful tool to transform them into processable materials but usually sacrifices the original structures and properties of value. Here we introduce a chemical modification of Curdlan, a β-1,3-glucan, via 4,6-acetalization. This modification has successfully combined a helix-forming ability of Curdlan with new solubility in organic media. Furthermore, it has operationalized efficient cohelical crossovers (CCs) among the helices to demonstrate the formation of an extensive supramolecular network that goes well beyond the nanoscopic regime, allowing for preparation of flexible self-supporting films with macroscopic dimensions. This protocol, which is now viewed as supramolecular polymerization of a helical polysaccharide macromer, can add a new dimension to "polysaccharide nanotechnology", opening a door for the creation of unconventional polymer materials based on the cohelical crossover network (CCN).

Background The dynamic behavior of water molecules remains an important subject for understanding human skin. The change in the dynamics of water molecules from those in bulk water can be effectively observed by dielectric spectroscopy. To study water in the human skin in vivo, non‐invasive and non‐destructive measurements are essential. Since many unknowns remain from previous research, in this report we employ a two‐layer dielectric model to evaluate the penetration depth of the electric field and use the results in measurements on human skin. Materials and Methods We used open‐ended coaxial probes with different diameters to perform time‐domain reflectometry (TDR) measurements for an acetone‐Teflon double‐layer model and for human skin from various parts of the body. Results The electric‐field penetration depth obtained from model measurements increases with the increasing outer diameter of open‐ended coaxial electrodes. For skin measurements, the relaxation strength corresponding to the water content shows a clear dependence on the epidermal thickness of the measured body parts. Conclusion We determined the depth distribution of the water content of skin from results of dielectric measurements obtained using electrodes with various electric‐field penetration depths. We found exponential decays with the thickness of the epidermis of each body part for several examinees. This study suggests an effective method for detailed evaluations of human skin.

The dynamics of a hydrogen bonding network (HBN) relating to macroscopic properties of hydrogen bonding liquids were observed as a significant relaxation process by dielectric spectroscopy measurements. In the cases of water and water rich mixtures including biological systems, a GHz frequency relaxation process appearing at around 20 GHz with the relaxation time of 8.2 ps is generally observed at 25 &deg, C. The GHz frequency process can be explained as a rate process of exchanges in hydrogen bond (HB) and the rate becomes higher with increasing HB density. In the present work, this study analyzed the GHz frequency process observed by suitable open-ended coaxial electrodes, and physical meanings of the fractal nature of water structures were clarified in various aqueous systems. Dynamic behaviors of HBN were characterized by a combination of the average relaxation time and the distribution of the relaxation time. This fractal analysis offered an available approach to both solution and dispersion systems with characterization of the aggregation or dispersion state of water molecules. In the case of polymer-water mixtures, the HBN and polymer networks penetrate each other, however, the HBN were segmented and isolated more by dispersed and aggregated particles in the case of dispersion systems. These HBN fragments were characterized by smaller values of the fractal dimension obtained from the fractal analysis. Some examples of actual usages suggest that the fractal analysis is now one of the most effective tools to understand the molecular mechanism of HBN in aqueous complex materials including biological systems.

Polycarboxylic acid-based superplasticizers are being used for various fields of concrete work, however little has reported on changing basic performance by thermal fluctuation. In this study, heating superplasticizers itself is hereinafter as referred to as “thermal stimulation”, the effect of thermal stimulation and heat retention of superplasticizer on the fresh mortar, moreover the influence of molecular structural changed of superplasticizer by thermal stimulation were investigated. As the result, it was confirmed that improving fluidity of the mortar flow on this condition the highly heat temperature and heat over a long time by thermal stimulation of superplasticizer. In addition, it turned out that this phenomenon was caused molecular structural changed by thermal stimulation, and the result was revealed that the effect of thermal stimulation varies according to the type of polymer.

In this study, broadband dielectric spectroscopy and differential scanning calorimetry (DSC) measurements are performed to study the dynamics of water and polymers in an aqueous solution of poly(vinylpyrrolidone) (PVP) with concentrations of 60, 65, and 70 wt % PVP in a temperature range of 123-298 K. Two distinct relaxation processes, l- and h-processes, which originate from the segmental chain motion of PVP and the primary relaxation process of water, respectively, are observed simultaneously. The relationship between l- and h-processes and their temperature dependences mimic those of the α-process and Johari-Goldstein β-process, which are observed in ordinal glass formers. The relaxation time of the l-process, τl, obeys the Vogel-Fulcher (VF)-type temperature dependence, and the glass-transition temperature of the l-process, Tg,l, which is defined by the temperature that is reached in a τl of 100-1000 s, shows good agreement with the calorimetric Tg obtained by DSC. The temperature dependence of the relaxation time of the h-process, τh, exhibits a crossover from VF to Arrhenius behavior at the so-called fragile-to-strong transition (FST) of water at Tg,l. The temperature dependence of the relaxation strength of the h-process, Δεh, increases with a decrease in temperature from 298 K to Tg,l. Below Tg,l, Δεh is nearly constant or slightly decreases with decreasing temperature. According to previous studies on aqueous solutions of sugars and alcohols, the Δε of the ν-process, which originates from local motion of water, decreases with decreasing temperature above the Tg of the α-process, which originates from the cooperative motion of the solute and water. Therefore, the l-process in the PVP-water mixture is not a result of the cooperative motion of PVP and water but rather a result of the polymer-polymer cooperative motion of PVP. In addition, agreement among Tg,l, the temperature of the FST of water, and calorimetric Tg suggests that the FST of water occurs at Tg.

Dynamics of solvent molecules restricted in poly (acryl amide) gels immersed in solvent mixtures of acetone&ndash, 1,4-dioxane&ndash, and dimethyl sulfoxide&ndash, water were analyzed by the time domain reflectometry method of dielectric spectroscopy and the pulse field gradient method of nuclear magnetic resonance. Restrictions of dynamic behaviors of solvent molecules were evaluated from relaxation parameters such as the relaxation time, its distribution parameter, and the relaxation strength obtained by dielectric measurements, and similar behaviors with polymer concentration dependences for the solutions were obtained except for the high polymer concentration in collapsed gels. Scaling analyses for the relaxation time and diffusion coefficient respectively normalized by those for bulk solvent suggested that the scaling exponent determined from the scaling variable defined as a ratio of the size of solvent molecule to mesh size of polymer networks were three and unity, respectively, except for collapsed gels. The difference in these components reflects characteristic molecular interactions in the rotational and translational diffusions, and offered a physical picture of the restriction of solvent dynamics. A universal treatment of slow dynamics due to the restriction from polymer chains suggests a new methodology of characterization of water structures.

Dynamics of Hydrogen Bonding Network (HBN) relating to macroscopic properties of hydrogen bonding liquids were observed as the largest relaxation process by dielectric spectroscopy measurements. In the cases of water and water rich mixtures including biological systems, a GHz frequency relaxation process appearing at around 20GHz with the relaxation time of 8.2ps is generally observed at 25°C. The GHz frequency process can be explained as a rate process of exchanges in HB and the rate becomes higher with increasing HB density. In the present work, we analyzed the GHz frequency process and clarified physical meanings of the fractal nature of water structures in various aqueous systems. Dynamic behaviors of HBN were characterized by a combination of the average relaxation time and the distribution of the relaxation time. The fractal analysis offered an available approach to both solution and dispersion systems with characterization of the aggregation or dispersion state of water molecules. In the case of polymer-water mixtures, the HBN and polymer networks well penetrate each other. However, the HBN were segmented and isolated more by dispersed and aggregated particles in the case of dispersion systems. These HBN fragments were dominantly evaluated by smaller values of the fractal dimension obtained from the fractal analysis, but it is also related with other two parameters. The fractal analysis is now one of the most effective tools to understand molecular mechanism of HBN in aqueous complex materials including biological systems.

Cloud points of poly( N-isopropylacrylamide) in aqueous mixed solvents, with methanol as the cosolvent, are experimentally measured for polymer concentrations varied up to as high as the weight fraction 0.25. They are shown to form closed loops on the ternary phase plane in the temperature region between 5 and 30 °C, and hence co-nonsolvency is complete. Miscibility loops shrink by cooling, or equivalently, they exhibit lower critical solution temperature behavior. For a fixed polymer concentration, there is a composition of the mixed solvent at which the cloud-point temperature takes the lowest value. This minimum cloud-point temperature composition of the mixed solvent turned out to be almost independent of the polymer concentration, at least within the measured dilute region below the weight fraction 0.25. On the basis of the assumption that the phase separation is closely related to the preferential adsorption of the solvents by hydrogen bonding, we employ a model solution of Flory-Huggins type, augmented with direct and cooperative polymer-solvent hydrogen bonds, to construct the ternary phase diagrams. Theoretical calculation of the spinodal curves is performed, and the results are compared with the obtained experimental cloud-point data. The effect of molecular volume of the cosolvent is also studied within the same theoretical framework. Possibility for a upper critical solution temperature co-nonsolvency to appear for cosolvents with larger molecular volume is discussed.

Broadband dielectric measurements of fructose–water mixtures with various fructose concentrations, C f (wt.%), in the range of 5–94.6 wt.% were carried out in the frequency range of 2 mHz–50 GHz at 25 and 0 °C, to clarify the dynamics of water and fructose molecules in the mixtures from liquid to glass states as a function of C f . For the mixtures with C f below 45 wt.%, a single relaxation process originating from the reorientational motion of water, i.e., ν relaxation, was observed. In contrast, in the mixtures with C f above 45 wt.%, in addition to the ν relaxation, α relaxation resulting from the cooperative motion of two components appears at a lower frequency than that of the ν relaxation. The temperature dependences of the relaxation time and strength of the α and ν relaxations are governed by the deviation from the glass transition temperature. Similarly, the concentration dependences of the relaxation time and strength are governed by the deviation from the glass transition concentration, which was defined as the concentration at which the relaxation time is 100 s. This means that the temperature–concentration superposition appears to be valid for the ν and α relaxations.

Broadband dielectric spectroscopy measurements were performed on partially crystallized gelatin–water mixtures with gelatin concentrations of 1–5 wt % for temperatures between 123 and 298 K to study the dynamics of ice. These systems contain only hexagonal ice. Nevertheless, four dielectric relaxation processes of ice were observed. At temperatures below the crystallization temperature, a loss peak was observed, and it separated into four loss peaks at around 225 K. Using the temperature and concentration dependencies of these relaxation processes, we confirmed that these four processes originated from ice. For the relaxation time of ice, τice, the deviation of the temperature dependence of τice from the Arrhenius type is larger for the relaxation process at the higher-frequency side. For the temperature dependence of τice for the dominant process, three temperature ranges with different activation energies, Ea, were investigated. The intermediate-temperature range of τice with the smallest Ea decreased a...

The temperature-gradient induced migration of biomolecules, known as thermophoresis or thermodiffusion, changes upon ligand binding. In recent years, this effect has been used to determine protein-ligand binding constants. The mechanism through which thermodiffusive properties change when complexes are formed, however, is not understood. An important contribution to thermodiffusive properties originates from the thermal response of hydrogen bonds. Since there is a considerable difference between the degree of solvation of the protein-ligand complex and its isolated components, ligand-binding is accompanied by a significant change in hydration. The aim of the present work is therefore to investigate the role played by hydrogen bonding on the change in thermodiffusive behaviour upon ligand binding. As a model system we use cyclodextrins (CDs) and acetylsalicylic acid (ASA), where a quite significant change in hydration is expected, and where no conformational changes occur when a CD-ASA complex is formed in aqueous solution. Thermophoresis was investigated in a temperature range from 10 to 50°C by infrared thermal diffusion forced Rayleigh scattering (IR-TDFRS). NMR measurements were performed at 25°C to obtain information about the structure of the complexes. All CD-ASA complexes show a stronger affinity towards regions of lower temperature as compared to the free CDs. We found that the temperature sensitivity of thermophoresis correlates with the 1-octanol/water partition coefficient. This observation not only establishes the relation between thermodiffusion and the degree of hydrogen bonding, but also opens the possibility to relate thermodiffusive properties of complexes to their partition coefficient, which can not be determined otherwise. This concept is especially interesting for protein-ligand complexes where the protein undergoes a conformational change, different from the CD-ASA complexes, giving rise to additional changes in their hydrophilicity.

Water structures in protein–water mixtures and cheeses were examined by Time Domain Reflectometry (TDR) and Nuclear Magnetic Resonance (NMR). The relaxation time obtained from TDR increased and the diffusion coefficient obtained from NMR decreased with increasing protein concentration, even if those physical quantities and time scales of respective observation techniques were considerably different. The correlation of these dynamic behaviors obtained from TDR and NMR is also found for water structures in cheeses. Fractal analysis of protein solutions by TDR measurements suggested that water structures in both systems were same with usual dispersion systems much more than solution systems. The fractal analysis with the τ– β diagram using geometric characteristics of the whole diagram is effective to characterize various water structures.

The glass transition of partially crystallized gelatin-water mixtures was investigated using broadband dielectric spectroscopy (BDS) over a wide range of frequencies (10 mHz to 10 MHz), temperatures (113-298 K), and concentrations (10-45 wt %). Three dielectric relaxation processes (processes I, II, and III) were clearly observed. Processes I, II, and III originate from uncrystallized water (UCW) in the hydration shells of gelatin, ice, and hydrated gelatin, respectively. A dynamic crossover, called the Arrhenius to non-Arrhenius transition of UCW, was observed at the glass transition temperature of the relaxation process of hydrated gelatin for all mixtures. The amount of UCW increases with increasing gelatin content. However, above 35 wt % gelatin, the amount of UCW became more dependent on the gelatin concentration. This increase in UCW causes a decrease in the glass transition temperature of the cooperative motion of gelatin and UCW, which appears to result from a change in the aggregation structure of gelatin in the mixture at a gelatin concentration of approximately 35 wt %. The temperature dependence of the relaxation time of process II has nearly the same activation energy as pure ice made by slow crystallization of ice Ih. This implies that process II originates from the dynamics of slowly crystallized ice Ih.

We performed an experiment of broadband dielectric relaxation spectroscopy (BDS) to study the molecular dynamics of an aqueous pullulan solution as a function of pullulan concentration. The frequency range of the BDS experiment is 40 Hz to 50 GHz, and the solution temperature is set at T = 25.0 °C. Two relaxation processes originating from pullulan and water molecules are obtained in the megahertz and gigahertz regions, respectively. Additionally, the electrode polarization and the contribution of dc conductivity are also observed at lower frequencies. The relaxation process at a frequency higher than 10 GHz is associated with the primary process of water (h-process), and that at 100 MHz is attributed to the local chain motion of pullulan (m-process). Impurities in the aqueous solutions, which are practically disregarded in the analysis of polysaccharide solutions, affect the quality of the relaxation spectrum. Thus, the purification of pullulan sample is carried out by methanol precipitation from aqueous pullulan solution. This iterative purification reduces the contributions of electrode polarization and DC conductivity, which enables the clear observation of the relaxation of the m-process. It was found that the relaxation times of the m- and h-processes increase with pullulan concentration. The relaxation strength of the m-process shows increasing behavior with increasing pullulan concentration, whereas the relaxation strength of the h-process decreases with increasing pullulan concentration. It is suggested that the relaxation strength of the m-process is mainly determined by the magnitude of the dipole moment of solvent molecules. The relaxation process of water (h-process) is affected by the interactions of pullulan chains. The interdependence between the h- and m-processes is discussed with respect to the findings of recent dielectric relaxation studies on aqueous polymer solutions.

Stereoregular poly( N -isopropylacrylamide)s with controlled content of isotactic dyads have recently been synthesized, and interesting interference phenomena between LCST phase separation and high-temperature reversible gelation have been observed in their aqueous solutions. We develop a model solution in which dehydrated stereo-regular isotactic segments on polymers are driven into intermolecular cross-links leading to gelation. We theoretically calculate the phase diagrams for the varied content isotactic dyads and compare with the experimental data.

Dielectric relaxation caused by the segmental motion of poly(vinyl pyrrolidone) (PVP) was observed in solutions at 25 °C with various solvents, that is, chloroform, water, and mono- and dihydroxyl alcohols with dielectric constants ranging between 5 and 78. The relaxation strength of the segmental motion of PVP varies with the solvent. The magnitudes of the effective dipole moment of the repeat unit of PVP in solutions with various solvents calculated using the Onsager equation depends simply on the dielectric constant of the solvent at higher frequency.

Cyclodextrins are cyclic oligosaccharides which are interesting as drug delivery systems, because they can be used as containers for pharmaceutical substances. We studied the Ludwig-Soret effect of $\alpha$-, $\beta$-, $\gamma$- and methyl-$\beta$-cyclodextrin in water and formamide by infrared thermal diffusion forced Rayleigh scattering (IR-TDFRS).In water the Soret coefficient, $S_{\mathrm{T}}$, of $\alpha$-, $\beta$- and $\gamma$-cyclodextrin increases with increasing temperature and shows a sign change from negative to positive around $T=35^\circ$C, while $S_{\mathrm{T}}$ of methyl-$\beta$-cyclodextrin is positive in the entire investigated temperature. In formamide $S_{\mathrm{T}}$-values of all cyclodextrins coincide and show a slight decrease with temperature. We discuss the obtained results and relate the $S_{\mathrm{T}}$-values to the different hydrogen bonding capabilities of the cyclodextrins and the used solvents. It turns out that the change of $S_{\mathrm{T}}$ with temperature correlates with the partition coefficient, log~$P$, which indicates that more hydrophilic substances show a more pronounced temperature sensitivity of $S_{\mathrm{T}}$. Additionally we obtained a surprising result measuring the refractive index contrast factor with temperature, $(\partial n/\partial T)_{c,p}$ of cyclodextrins in formamide, which might be explained by a complex formation between cyclodextrins and formamide.