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  • 1
    Electronic Resource
    Electronic Resource
    Picosecond relaxations in model substances for proteins: A millimeter-wave investigation on crystalline alkyl amides (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 677-691 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dielectric absorption at millimeter-wave (mm-wave) frequencies (50-150 GHz) of N-methylacetamide (NMA), N,N-dimethylacetamide (DiNMA), and N,N-dimethylacrylamide (DiNMAcry) is measured. Measurements are performed using the oversized-cavity technique in the temperature range from liquid helium to room temperature. Additionally, a mm-wave interferometeric measurement at room temperature is made. NMA and DiNMAcry exhibit monotonic increases of the absorption coefficient with temperature as well as with frequency. For DiNMA a monotonic increase of the absorption coefficient with frequency is also found, while the absorption coefficient as a function of temperature shows a pronounced maximum at approximately 30 K. At this maximum the absorption coefficient of DiNMA exceeds those of NMA and DiNMAcry by about two orders of magnitude. The dielectric behavior of the three substances can be described by relaxation processes in asymmetric double-well potentials. For the low-temperature relaxation in DiNMA the double well could be established by two possible positions of the molecule in the crystal that are separated by a rotational movement. Hydrogen bonds and long side chains may hinder these relaxational movements in NMA and DiNMAcry, respectively, and thereby account for their comparatively lower absorption. The results are compared with similar results recently obtained on proteins and synthetic biopolymers.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250411
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  • 2
    Electronic Resource
    Electronic Resource
    Relaxation processes on a picosecond time scale in hemoglobin and poly(L-alanine) observed by millimeter-wave spectroscopy (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 1715-1729 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Broadband measurements of the millimeter-wave and far-ir absorption (10-104 GHz) of lyophilized hemoglobin are reported. Additionally, the absorption of poly(L-alanine) and crystalline L-alanine at 70 GHz was measured for comparison. All measurements were extended over the temperature range from liquid helium to room temperature. For the millimeter range, this was attained by using the novel oversized-cavity technique. It was found that the millimeter-wave absorption of the materials increased nearly exponentially with temperature and increased as ν1.2-ν2 with frequency. The far-ir absorption of hemoglobin showed broadbands with almost no temperature dependence. The frequency and temperature dependence of the millimeter-wave absorption is quantitatively described as due to three distinct relaxation processes on a picosecond time scale occurring in asymmetric double-well potentials. These processes are most probably assigned to the NH⃛OC hydrogen bonds of the peptide backbone.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360220708
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  • 3
    Electronic Resource
    Electronic Resource
    Evidence of dynamic heterogeneity as obtained from dielectric and brillouin light-scattering studies of poly(n-hexylmethacrylate) (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 1391-1401 
    Details
    ISSN: 0887-6266
    Keywords: Rayleigh-Brillouin spectroscopy ; dielectric relaxation spectroscopy ; poly(n-hexylmethacrylate) ; cooperative length of glass transition ; splitting between α- and β-relaxation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We report dielectric relaxation and Rayleigh-Brillouin spectroscopic measurements on the side chain polymer poly(n-hexylmethacrylate), PHMA (Tg = 268 K), exhibiting a broad glass transition region. The dielectric loss curves can be represented by single Havriliak-Negami functions in the temperature range of 260-450 K. The width of the distribution relaxation function is a decreasing function of temperature up to T = 333 K ≊ 1.24 × Tg and remains virtually constant above that temperature. This is interpreted as marking the merging of the α-process with a slow β-relaxation in agreement with the value of the cooperativity length associated with the α-mode. Hence above that temperature, the relaxation times confirm well to an Arrhenius temperature dependence. The hypersonic dispersion deduced from the Brillouin spectra (210-550 K) surprisingly peaks at temperatures near Tg which bears no relation to the main α-relaxation. This structural relaxation is rather associated with the side hexyl group motion showing striking resemblance with the hypersonic dispersion in molecular liquids. It is conceivable that the observed damping in PHMA is dynamically related to the internal plasticization effect of the hexyl group. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Double ferroelectric-to-paraelectric transition in 70/30 vinylidene fluoride-trifluoro ethylene copolymer as revealed by dielectric spectroscopy (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1449-1455 
    Details
    ISSN: 0887-6266
    Keywords: ferroelectric copolymers ; curie temperature ; dielectric relaxation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The variation of dielectric properties with temperature in the 1 kHz to 1 GHz frequency range for the 70/30 copolymer of vinylidene fluoride with trifluoroethylene has been associated to two processes: the β relaxation process associated with the glass transition of the amorphous phase and the ferroelectric-to-paraelectric crystal transition. The β process follows a Vogel-Fülcher behavior exhibiting an anomaly in the vicinity of the crystal transition. Analysis of the ferroelectric-to-paraelectric Curie transition reveals the existence of a double relaxation maximum in the dielectric losses. Results have been interpreted in terms of the Havriliak-Negami relaxation function. The variation of the relaxation strength and of the broadening parameter has been investigated as a function of temperature. The obtained results are discussed in terms of a two-step phase transformation mechanism for the Curie transition: a first transition from the low temperature “all-trans” ferroelectric phase to a more defective phase; a second transition from the latter phase to the final paraelectric structure. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090320816
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  • 5
    Electronic Resource
    Electronic Resource
    Collective and molecular dynamics in ferroelectric liquid crystals: from low molar to polymeric and elastomeric systems (1992)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 3 (1992), S. 249-255 
    Details
    ISSN: 1042-7147
    Keywords: Ferroelectric liquid crystals ; Polymers ; Dielectric spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Broadband dielectric spectroscopy delivers in the frequency range from 10 Hz to 1010 Hz two collective dielectric loss processes (soft and Goldstone modes) and one molecular relaxation (β-relaxation). The soft mode and Goldstone mode are assigned to the fluctuation of the amplitude and the phase of the helical superstructure. The β-relaxation corresponds to the libration (hindered rotation) of the mesogene around its long molecular axis. At the SmA-SmC* phase transition this process does not split or broaden, and the temperature dependence of its relaxation rate does not show any deviation from an Arrhenius-like behavior. Its dielectric strength does not decline at the SmA-SmC* phase transition. These experimental findings are in contrast to the common explanation of the origin of the saturation polarization (“induced spontaneous polarization”), which is based on the existence of a “free” rotation inside the SmA phase and its strong hindrance in the ferroelectric SmC* phase. Furthermore, the high frequency results require a reformulation for the (generalized) Landau theory as applied to the SmA-SmC* phase transition. In comparing low molar mass and polymeric (elastomeric) FLC, the collective and molecular dynamics are qualitatively similar, independent of the molecular architecture (e.g. side-chain, combined main- and side-chain or crosslinked systems).
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1992.220030509
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  • 6
    Electronic Resource
    Electronic Resource
    Editorial - ferroelectric liquid crystalline polymers (1992)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 3 (1992), S. 195-195 
    Details
    ISSN: 1042-7147
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1992.220030501
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  • 7
    Electronic Resource
    Electronic Resource
    Polymeric liquid crystals: structural basis for ferroelectric and nonlinear optical properties (1992)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 3 (1992), S. 211-217 
    Details
    ISSN: 1042-7147
    Keywords: LC polymers ; LC elastomers ; Ferroelectricity ; Piezoelectricity ; Nonlinear optics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper describes the rational design and structure-property relations in three different types of polar LC polymers with interesting material properties, as follows. (i) Chiral LC polymers, which are functionalized with crosslinkable groups, can be converted into LC elastomers with chiral smectic C* phases. The mechanical orientability of these elastomers leads to new piezoelectric materials. (ii) The curing (dense crosslinking) of a polymer matrix provides one possibility of stabilizing the polar order of dye molecules, which is necessary for frequency doubling. Additionally, LC phases can help to stabilize this polar structure, which leads to large and stable nonlinear optical coefficients. (iii) Polymer analogous esterifications offer a convenient method for the synthesis of chiral smectic C* polymers with large ferrolectric polarizations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1992.220030504
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  • 8
    Electronic Resource
    Electronic Resource
    Dielectric relaxation and conductivity in polyelectrolyte - surfactant complexes (1996)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 47 (1996), S. 460-465 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dielectric and conductivity behavior of some selected solid polyelectrolyte-surfactant complexes (PE-surf) is characterized by broadband dielectric spectroscopy in the frequency range 10-2-107 Hz. Depending on phase-morphology and volume fraction of alkyl-tails, electrical conductivities at room temperature of up to 10-4 S/cm are found. In addition, the behavior at low temperatures is characterized by two distinct β-relaxations which show an Arrhenius-like activation, and their relaxation strength depends on temperature, in contrast to the standard behavior of dielectric media. The relaxations are assigned to surfactant movements, the number or strength of which increase with temperature, which are obviously important already well below the glass transition temperature of the ionic layers. Doping of a selected complex showing a rather high basic conductivity with LiClO4 results in a decrease of the conductivity, which is explained by an increase in the glass transition temperature of the ionic layer.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1996.010471007
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  • 9
    Electronic Resource
    Electronic Resource
    Picosecond relaxations in hydrated polyamide-6 observed by millimeter-wave spectroscopy (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 23 (1985), S. 1247-1254 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Absorption measurements at millimeter-wave frequencies (50-151 GHz) are reported for dried and hydrated polyamide-6. The measurements were extended over the temperature range from liquid helium to room temperature using the oversized-cavity technique. For dried polyamide-6 (water content ≤ 0.5% w/w), a nearly linear increase with frequency and an exponential increase with temperature of the absorption coefficient is found between 50 and 300 K. This frequency and temperature dependence is described by relaxation processes in asymmetric double-well potentials. The observed relaxation times are on a picosecond time scale, thus suggesting an assignment to the NH…OC hydrogen bonds and the adjacent peptide unit (O=C—N—H). Hydration results in an increase of the absorption over the whole temperature and frequency range. This is attributed to the fact that the water of hydration is adsorbed in the neighborhood of the hydrogen bonds and changes their dynamical properties. This interpretation is supported by IR-spectroscopic measurements of the shift of amide I and amide II after hydration.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.180230615
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  • 10
    Electronic Resource
    Electronic Resource
    Local dynamics in a thermotropic terpolyester as revealed by dynamic mechanical analysis, 2H NMR and dielectric spectroscopy (1996)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 47 (1996), S. 429-435 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dynamic mechanical, 2H NMR and dielectric spectroscopy techniques were used to identify the nature of the local motions involved in the secondary relaxations of a thermotropic aromatic terpolyester prepared from para-hydroxybenzoic acid, hydroquinone and isophthalic acid. Three secondary relaxations, denoted β, γ, and δ, were detected. A β relaxation, pointed out by dynamic mechanical measurements, is quite close to the large amplitude π-flip processes observed by 2H NMR. Correlated motions of the para-substituted rings and adjacent carbonyl groups may also participate in the β process. Then, at lower temperatures, a γ process is detected by both dielectric and dynamic mechanical experiments. It is assigned to small amplitude oscillations of the isophthalic acid units of the HBA33 polymer. At high temperatures, a heavy overlap of broad rate distributions for the β and γ processes observed in the measurements precludes a more detailed analysis. A dielectric relaxation, denoted δ relaxation, is observed at very low temperatures. It likely comes from motions of a very small number of water molecules trapped in the structure of the terpolyester.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1996.010471002
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