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In a few decades, several characteristic regimes and subregimes have been theoretically presented as functions of concentration C and contour length for flexible polyelectrolyte solutions. However, experimentally only the dilute and semidilute regimes have been well acknowledged. In this study, solutions of sodium poly(styrene sulfonate) are studied at various concentrations ranging from the semidilute regime to the bulk through the concentrated regime using small-angle and intermediate-angle x-ray scattering techniques. We have observed a single scattering peak being characteristic of polyelectrolyte solutions until C=4.1 mol/l. Above C=4.9 mol/l, such a characteristic peak disappears and instead, another new peak appears at higher q’s. In the plot of the maximum position qmax vs C, two crossover concentrations are found at C**=1.2 mol/l and C***=4.5 mol/l. The former is a continuous crossover from qmax∼C1/2 to qmax∼C1/4 which can be assigned to the crossover of the semidilute-to-concentrated regime, whi...

Inelastic and quasielastic neutron-scattering measurements have been performed on an amorphous poly(ethylene terephthalate) (PET) fiber in parallel and perpendicular scattering geometries, i.e., when the fiber axis f is parallel and perpendicular to the scattering vector Q, respectively. The so-called boson peak is observed at around −1.4 meV in neutron energy transfer at low temperatures below about 150 K in both the geometries; as temperature increases, the fast process of picosecond order appears at a certain temperature below the glass-transition temperature Tg(=348 K). Although no drastic differences in the dynamics can be observed, a closer look at the spectra revealed some interesting features of the low-energy modes. From the mean-square displacements evaluated with two different energy resolutions, it was found that the fast process appears only in the direction perpendicular to the polymer chain (not the fiber axis f) in the energy region between −1 and −0.2 meV. In the inelastic scattering spec...

We report quasielastic neutron scattering results on an amorphous polyimide (AURUM) in a temperature range from 10 to 300 K below the glass transition temperature Tg(=250 °C). As temperature increases from 10 K, anharmonic excess scattering intensity appears at around 200 K or about 300 K below Tg. This excess scattering is very similar to the so-called fast process in picosecond order observed for glass-forming polymers as well as organic and inorganic low molecular weight glass-forming materials. We first analyzed the spectra in a simple way assuming validity of the Bose scaling for the vibrational density of states and a Lorentzian for the additional relaxational process, and found that the excess scattering intensity appears in the frequency range below the Boson peak and the characteristic time is independent of temperature which are common features for the fast processes reported previously. The second analysis using the recent vibration-relaxation (VR) model, which is more realistic, indicated that...

We have developed a novel cryostat in which glassy states of molecular substances are formed by deposition of their vapor on a cold substrate. The glassy samples are subjected to in situ inelastic neutron scattering experiments. By the use of this cryostat, the glassy state of propylene(CH2=CHCH3) prepared at 20 K was examined on an inverted geometry time-of-flight neutron spectrometer in the energy range below 10 meV. The measurement was performed also on the glassy sample annealed at the glass transition temperature (55 K). A broad excitation peak (boson peak) was found at around 3 meV in the S(2θ,ω) spectra of the as-deposited and annealed samples. The absolute densities of vibrational states G(ω) were derived by combining the neutron spectra and the heat capacity data of a similar compound 1-butene (CH2=CHCH2CH3). The number of vibrational modes associated with the low-energy excitation was 1.64 per molecule for the as-deposited sample and 1.34 for the annealed sample. The boson peak energy depends on...

We have studied the glass transition dynamics of trans‐1,4‐chloroprene from microscopic view points using a quasielastic neutron scattering technique in a time range of ∼4×10−13 to ∼4×10−10 s. It was found that the so‐called fast process of picosecond order appears at around the Vogel–Fulcher temperature T0, similarly to cis‐1,4‐polybutadiene having no large side groups [J. Chem. Phys. 98, 8262 (1993)]. It is considered that the onset temperature at around T0 must be characteristic to polymers having no large side groups or no large internal degrees of freedom. In addition to the fast process, the slow process of subnanosecond order sets in at around the glass transition temperature Tg and the activation energy of the relaxation time was found to be ∼2.5 kcal/mol. The nature of the slow process is discussed in terms of conformational transition near Tg.

This paper presents the first neutron scattering measurement of 1,2‐1,4‐polybutadienes with varying microstructure. Incoherent inelastic scattering experiments have been performed in the range of moderate (ΔE≊300 μeV) and high (ΔE≊20 μeV) energy resolution. For the moderate resolution experiments the vibration–relaxation model has been used as a guideline for interpretation. The most striking influence of the microstructure variation can be found in the position of the boson peak. Its position at low temperature as well as its temperature dependence is significantly different among the measured samples. The high resolution data have been Fourier transformed into the time domain yielding the intermediate incoherent scattering function in a time range of 5,...,150 ps. There, the basic properties found for 1,4‐polybutadiene earlier could be reproduced (separation of α and βslow regimes of the slow relaxation, Kohlrausch–Williams–Watts function with β≊0.4). On the basis of the new data, no microstructure indu...

Glassy 1‐butene (CH2=CHCH2CH3) was studied by incoherent inelastic neutron scattering below 10 meV in the temperature range 18≤T≤80 K covering the glass transition temperature (Tg=60 K). A broad excitation peak due to the low‐energy excitation was found at 3–4 meV. The spectra corrected for the Bose factor could be scaled to a unique curve for temperatures below Tg. The absolute density of vibrational states was derived from the spectrum at 18 K and the previously measured heat capacity data. The number of vibrational states associated with the low energy excitation was 1.4 per molecule. This is much larger than those for SiO2 and other amorphous materials studied so far. The density of vibrational states was well reproduced by the soft potential model originally conceived for network glasses.

The dynamics of atactic polystyrene (PS) has been studied by a quasielastic neutron scattering technique in a temperature range of 21–475 K covering the glass transition temperature Tg (=373 K). The so‐called fast process in picosecond order is observed similarly to other glass‐forming materials in supercooled states so far reported. However, the onset temperature of the fast process is ∼170 K below Tg in PS, which is far below Tg in contrast to the previous observations. This result implies that the fast process is not necessarily the β process predicted by the recently noted mode coupling theory. By comparing the result of hydrogenated PS with that of partially deuterated polystyrene (PS‐d5) where only phenyl rings were preferentially deuterated, the origin of the fast process occurring far below Tg has been assigned to librational motion of phenyl rings, which is coupled with main chain motion near Tg. Analysis of the spectra by curve fit has suggested that the nature of the fast process changes at a t...

Dynamics of amorphous cis‐1,4‐polybutadiene was studied by incoherent inelastic and quasielastic neutron scattering below 10 meV in a wide temperature range covering the glass transition temperature Tg. The spectra at low temperatures below Tg show a broad excitation peak at about 2–3 meV, which is the so‐called low‐energy excitation and believed to be an origin of anomalous thermal properties of amorphous materials at low temperatures. It was found that the temperature dependence of the low‐energy excitation intensity can be normalized by the Bose factor at temperatures low enough below Tg. With increasing temperature, a very fast motion appears in the energy range below ∼4 meV at around the Vogel–Fulcher temperature T0, which is ∼50 K below Tg. This fast motion is often interpreted as the β process predicted by the mode coupling theory. In this paper, both the low‐energy excitation and the fast motion were analyzed in terms of a common microscopic picture, i.e., an asymmetric double well potential. The ...

In order to investigate low‐energy excitations below 10 meV, inelastic neutron‐scattering measurements have been carried out on various organic amorphous polymers at 10 and 50 K and three inorganic glasses at 150 and 295 K. It was found that a broad excitation peak is observed for all amorphous materials in the ω range of 1.5–4.0 meV irrespective of different chemical structures. On the other hand, highly crystalline polyethylene with a degree of crystallinity 0.96 shows no such broad peak, indicating that the low‐energy excitation is characteristic of amorphous materials. We have employed an asymmetric double‐well potential as a common origin for the low‐energy excitation in amorphous materials and analyzed the results of amorphous polyisobutylene to confirm validity of this model and alternatively to determine parameters of the potential. Analysis of the temperature dependence of the inelastic‐scattering intensity of the low‐energy excitation leads to a concept of phonon‐assisted tunneling in the asymmetric double‐well potential.