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Order–order transitions during spin-coating processes in symmetric and asymmetric poly(styrene-block-2-vinylpyridine) (PS-b-P2VP) were investigated by using grazing incidence small-angle X-ray scattering (GISAXS). When the composition was symmetric (e.g., the copolymer P2VP volume fraction, fP2VP, was 0.50), we found that loose-packed nanocylindrical structures formed after the transition from micelles to a body-centered cubic (BCC) lattice structure during evaporation. After the BCC (110) plane aligned perpendicular to the substrate, microdomains coalesced into a cylindrical structure. This coalescence was caused by the convection effect of the solvent, and vitrification of PS and P2VP further prohibited transitions from the cylindrical structure, although generally, the equilibrium morphology in the bulk state is lamellae. For an asymmetric composition with fP2VP = 0.70, lamellar structures formed perpendicular to the substrate. During evaporation, the micelles transformed to hexagonal close-packed (HCP...

We have investigated the inner structure of shear-induced precursor of shish kebab of isotactic polystyrene (iPS) above the nominal melting temperature Tm using microbeam wide-angle X-ray scattering. We first studied the effects of the shear rate on the inner structure and found that the crystallinity in the precursor increased with the shear rate while the crystallite size was independent of that. This was explained in terms of effects of chain entanglements on shear-induced crystallization. We also studied effects of annealing below the nominal melting temperature Tm and found no changes in the crystallites size before and after the annealing, suggesting that the crystallites did not grow into shishs during the annealing below Tm although the kebabs grew.

We have studied kinetics of polymerization-induced phase separation of epoxy solution in oligoethylene glycol using light scattering and an optical microscope. It was found that special double droplet morphology was observed only in a very narrow range of epoxy fraction, which depended on the reaction temperature. In the narrow range the phase separation rate was very fast, and the bicontinuous structure which was typical in spinodal decomposition-type phase separation was observed only in the very early stage, suggesting that the solutions in the narrow fraction range entered directly the spinodal decomposition region without crossing the bimodal region. It is therefore considered that the temperature-dependent narrow fraction range corresponds to the trajectory of the critical point of the phase separation curve in the fraction–temperature diagram.

We studied the structure development in the dewetting process of deuterated polystyrene (dPS) and poly(vinyl methyl ether) (PVME) thin films, which were prepared by a spin-coating method on a quartz substrate, after the temperature jump into the two-phase region, using time-resolved specular and off-specular neutron reflectivity (NR), specular X-ray reflectivity (XR), light scattering (LS), and optical microscope (OM) measurements. The OM and specular XR measurements showed that there clearly existed an incubation period before dewetting. In the incubation period, composition fluctuations between dPS and PVME were developed due to phase separation. The specular NR results revealed that composition fluctuations began to occur just after the temperature jump along the depth direction over the film, giving rise to the composition gradient heterogeneously over the film. Composition fluctuations were also observed in the in-plane direction by the off-specular NR and LS measurements: the off-specular NR measure...

Preparation of strong fiber with ultrahigh strength and modus is a dream of polymer scientists and engineers. It is believed that a shish-kebab is the structure origin of the ultrahigh strength and modulus fiber. This article presents our investigation on the inner structure of shish-kebab precursor of isotactic polystyrene in μm scale formed by shear flow above the nominal melting temperature Tm using microbeam wide- and small-angle X-ray scattering (WAXS and SAXS). The microbeam WAXS experiments indicated that the precursor included crystallites with degree of crystallinity of ∼0.15%, which had higher melting temperature than normal lamellar crystals, meaning that its size (the length) was longer in the c-axis of crystals than the normal lamellar crystals. The microbeam SAXS experiments confirmed that approximately 1% of the crystallites in the precursor were rather long in the direction of c-axis. It is expected that such crystallites work as an initiator of a shish when it is below Tm.

Local dynamics of para-substituted poly(1-chloro-2-phenylacetylene) (PCPA) derivatives was studied using quasielastic neutron scattering. Broadening of the dynamic scattering law (S(Q,ω)) was clearly observed for para-substituted PCPA derivatives even in the glassy state, and the observed S(Q,ω) was well fitted to a sum of narrow and broad Lorentzians, which represent the slow and fast motions, respectively. The half-width at half-maximum (Γ) of the narrow Lorentzian exhibited a positive correlation with the CO2 and CH4 permeability coefficients (P), while the Γ from the broad Lorentzian hardly changed despite of the variation of permeability coefficient, indicating that only the narrow component (i.e., the slow motion) contributes to the gas permeability. The Γ from the narrow component was approximately proportional to the diffusion coefficient (D) of the CO2 and CH4 gases, whereas it did not correlate with solubility coefficient (S). This implies that the local mobility affects the gas permeability thr...

In a previous paper [Polymer 2009, 50, 2095] we found that string-like objects were formed on the micrometer scale, after applying shear flow on melt of isotactic polystyrene (iPS) above its nominal melting temperature Tm, and assigned to precursors of shish-kebab (shear-induced precursor). In this paper we studied effects of a small amount of noncrystalline high molecular weight atactic polystyrene (aPS) in iPS on the shear-induced precursor formation above Tm (=223 °C). Polarized optical microscope (POM) measurements were mainly used to study the structure formation process of iPS and aPS/iPS blends under the chosen experimental conditions. It was found that there were more shear-induced precursors in aPS/iPS blend than in pure iPS at some shear conditions. This suggests that aPS can enhance the shear-induced precursor formation of iPS. The shear-induced precursors formed in the blends were as stable as those in pure iPS. Both could survive for more than 60 min at shear temperatures above Tm and melted ...

Dielectric behavior was examined for ternary blends of guestcis-polyisoprene (PI) chains, coguest PS chains, and host PS–PI–PS triblock copolymers. The guest PI chains had the molecular weight Mg-PI well below Mb-PI of the PI blocks and were mixed in the spherical PI domains formed in the copolymers. PI has the type-A dipoles parallel along the chain backbone and its end-to-end vector fluctuation activates dielectric relaxation. The dielectric test was conducted at temperatures well below the glass transition temperature of the PS blocks, so that the PI blocks had their ends fixed on the glassy PS matrix and exhibited no end-to-end vector fluctuation. Thus, the slow dielectric response of the systems exclusively detected the global motion of the guest PI chains confined in the spherical PI domain. The dielectric mode distribution of the guest PI chains thus observed was broader than that of the same chains in bulk systems, reflecting the osmotic and spatial constraints on the chain dynamics in the spheric...

Effects of the addition of PDLA on the crystallization behavior of PLLA was investigated by means of differential scanning calorimetry, wide-angle X-ray diffraction, melt rheology, and polarized optical microscopy. Nonisothermal and isothermal crystallization behavior of PLLA including low (l-PDLA) and high molecular weight PDLA (h-PDLA) were studied. PLLA/PDLA asymmetric blends form stereocomplex (SC) crystal and stay unmelted at 200 °C in the PLLA melt. Nonisothermal crystallization measurement from 200 °C showed monotonous rise in the crystallization temperature for PLLA/h-PDLA blend, while peculiar concentration dependence was observed for PLLA/l-PDLA blends. The acceleration effect was more pronounced in PLLA/h-PDLA, although the crystallinity of SC was lower than PLLA/l-PDLA blends, which implies the importance of higher order structure of SC for the crystallization of PLLA. From isothermal crystallization kinetics measurements, the acceleration effect in PLLA/h- and l-PDLA blends was found to enhan...

Density of the polyacrylamide ultrathin films has been studied using X-ray reflectivity technique. Two sources (one powder and another aqueous solution) of polyacrylamide were used to prepare spin coated films on silicon substrate. Light scattering measurements show that the polymer chains were unentangled in a concentrated (4 mg/ml) as well as in a dilute (2 mg/ml) solution prepared from the powder, whereas the solution (4 mg/ml) prepared by diluting the solution source shows entangled chain morphology. Three sets of films of different thicknesses were prepared using the three solutions by spin coating on silicon substrates. Comparison of X-ray reflectivity data for as prepared and dry films reveals that the shrinkage of the films decreases with increasing thickness. Average electron densities of the films were found to follow a trend of higher density for thinner films with a maximum increase of about 12% compared to the bulk. The densities of all the films irrespective of the nature of entanglement and concentration of their source were found to increase with spin speed of coating and attain saturation at higher speed. Absence of correlation between shrinkage and density data and the fact that the densities of all the films follow a master curve irrespective of their origin suggest that the higher density of the films result from the higher orientation of chains as a consequence of an interplay between stretching and stronger attractive interactions of polar nature., Comment: 6 figures

The mesomorphic phase of poly(butylene-2,6-naphthalate) (PBN) has been studied using wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). It was found that PBN showed a mesomorphic phase when it was rapidly quenched from the molten state to 0 °C. The mesomorphic PBN was nearly transparent solid in appearance and its structure in WAXD scale was an intermediate one between amorphous and crystal having smectic periodicity. With increasing the temperature, a portion of amorphous remaining in the quenched PBN transformed into the mesomorphic phase above 48 °C, and then the mesomorphic phase began to transform into the α-crystal above 71 °C. We propose that the mesomorphic phase of PBN has a glass transition temperature T g meso at 65 °C besides the normal glass transition temperature Tg for the isotropic glass at 41 °C.

Effects of the crystallization temperature on the crystal structure and its melting behavior of poly (l-lactic acid) (PLLA) have been investigated by means of wide-angle (WAXS) and small-angle (SAXS) X-ray scattering, optical microscopy, and differential scanning calorimetory (DSC). PLLA was found to crystallize as the α form when the crystallization temperature Tc was higher than 120 °C, while significant change in lattice parameters was seen for Tc's below 120 °C. The ratio of the a- and b-axis lengths begins to decrease with Tc below 120 °C and is 31/2 below 90 °C, which suggests a new crystalline form with hexagonal packing, namely, the α‘ form. The possible reason for α‘ formation is discussed. High-temperature WAXS and SAXS measurements showed that α‘ crystal transforms into ordered a form during heating. The transition takes place at 150 °C without a decrease in scattering intensity and without heating rate dependence. The mechanism for the transition is discussed.

Time-resolved light-scattering measurements have been performed on poly(vinyl alcohol) (PVA) in mixed solvents of dimethyl sulfoxide (DMSO) and water with various mixing ratios after quenching from...

We performed small-angle X-ray scattering (SAXS) measurements on crystallization processes of polyethylene blends of low molecular weight and ultrahigh molecular weight components with various blending ratios in order to clarify effects of ultrahigh molecular component on shish-kebab structure formation. Anisotropic scattering patterns due to kebab structure formation were observed above a certain concentration of ultrahigh molecular weight polyethylene. The critical concentration was about ∼0.1 wt % independent of the crystallization temperature below 125 °C, while it increased with the crystallization temperature above 125 °C. Analyzing the correlation between ultrahigh molecular weight component concentration and crystallization temperature in more detail, these results suggest that both the crystallization rate and the relaxation rate of the ultrahigh molecular weight component have significant effects on the shish-kebab formation process.

For a series of 1,4-butadiene (B)−styrene (S) symmetrical multiblock copolymers, BSB triblock, BSBSB pentablock, and BSBSBSB heptablock copolymers having the same block molecular weights and B/S composition, the rheological behavior and structure were examined in dibutyl phthalate (DBP) at 25 °C. DBP is an S-selective solvent, i.e., a good solvent for the S blocks and a poor solvent for the B blocks. The copolymer concentrations C (= 22−25 wt %) were chosen to be just above (by 1 wt %) respective microphase separation concentrations. In a well-equilibrated state, the copolymer/DBP solutions formed a bcc lattice of the spherical domains of unsolved B blocks bridged by the S blocks (lattice-type network), thereby exhibiting elastic behavior under small strains. This lattice-type network was disrupted under steady shear to lose its elasticity, and the heaviest disruption occurred at an intermediate shear rate close to the B/S concentration fluctuation frequency. The elasticity was recovered after cessation o...

We performed small-angle neutron and X-ray scattering (SANS and SAXS) measurements on an elongated blend of low molecular weight deuterated polyethylene (PE) and high molecular weight hydrogenated one (97.2/2.8) in a very wide range of scattering vector of 1 × 10-4−3 A-1 to elucidate hierarchic structure of the so-called shish-kebab. Comparing the SANS and SAXS data, we found that the hydrogenated high molecular weight PE formed a large and long object aligned along the elongation direction. The SANS data were analyzed in terms of the multicore−shell cylinder model, and we found that the long oriented structure had radius of ∼1 μm and length of ∼12 μm and included about three extended chain crystals with radius of ∼45 A. We believe that this oriented long object with a relatively low aspect ratio of about 12:1, which is called the row structure in this paper, is a precursor formed from deformation of network of high molecular weight components due to entanglements.

The crystallization process of isotactic polypropylene (iPP) by heating from the prequenched mesomorphic phase has been studied using wide-angle X-ray diffraction, small-angle X-ray scattering, and optical microscopy. Mesomorphic iPP as quenched shows the well-known nodular structure of ca. 100 A. In heating process the nodules grew larger keeping self-similarity, with the mesomorphic phase partially transforming into the crystalline phase inside the nodules. After reaching the isothermal process, the nodules stopped to grow at a certain quasi-equilibrium size depending on the annealing temperature. During the long annealing, the interface among the nodules became obscure, and the nodules in nanometer scale merge into larger structure of pure α-phase in micrometer scale. The relation between the quasi-equilibrium nodule size and the annealing temperature leads an extrapolated melting temperature of the mesomorphic phase, which is located above the equilibrium melting temperature of the α-crystal.

We studied crystallization process of isotactic polypropylene (iPP) under shear flow as a function of shear rate using time-resolved wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), depolarized light scattering (DPLS), and polarized optical microscopy (POM) to elucidate the formation mechanism of the so-called shish-kebab structure in a wide spatial scale from 0.1 nm to several tens of μm. In the time-resolved DPLS, SAXS, and WAXS measurements we observed the formation processes of the shish-like structure, the kebab structure, and the crystalline lattice (mostly in the kebab), respectively, and found that there were critical shear rates for the anisotropic structure formation in the DPLS, SAXS, and WAXS measurements. The values are very close each other, suggesting the anisotropic structure formations in both of the shish and the kebab are dominated by a common origin. Furthermore, comparing the onset times of intensities in DPLS, SAXS, and WAXS, we found that the onset of DPLS in...

The effect of isotacticity on the mesomorphic phase-forming properties of isotactic polypropylene (iPP) is reported. Only iPP having high isotacticity (iPP-HT) can form the mesomorphic phase by a rapid quench, but iPP having low isotacticity (iPP-LT) cannot form the mesomorphic phase though it crystallizes by the same quenching rate. These results suggest that the mesomorphic phase of iPP is closely related to the stereoregularity of the polymer chain. The mesomorphic phase in the iPP-HT shows longer regular 3/1 helices than in the crystalline iPP-LT. The structure and formation mechanism of the mesomorphic iPP are considered analogous to those of liquid crystals since the average length of the long regular 3/1 helices in the mesomorphic iPP acting as rodlike segments is sufficiently large to fulfill a criterion for the formation of liquid crystalline phase. From this criterion, the minimum requirement of isotacticity to form the mesomorphic phase is also estimated.

Rheological and structural properties were examined for a 30 wt % solution of a 1,4-butadiene−styrene−1,4-butadiene (BSB) triblock copolymer (MS = 108 × 103, MB = 13.3 × 103 for each B block) in an S-selective solvent, dibutyl phthalate (DBP). At equilibrium at 25 °C, a bcc lattice of the unsolved, soft (rubbery) B domains connected by the middle S blocks (a lattice-type network) was formed to exhibit the elastic behavior against small strains. This lattice-type network was disrupted under steady shear to lose its elasticity, and the strongest disruption occurred at an intermediate shear rate (γ) close to a frequency of B/S concentration fluctuation. This disruption behavior was similar to that of a BS/DBP diblock micellar lattice system. However, for the BSB/DBP system, an order of magnitude increase of γ resulted in a minor change (by a factor

In a nonpolar solvent such as benzene (Bz), living anionic chains having Li as the countercations generally aggregate with each other through Li at their ends. Specifically, the bianionic chains having Li at both ends form an aggregated network. For investigation of the dynamics of the aggregates, polybutadienyl dilithium (PBLi2) bianionic chains were polymerized in Bz, and their viscoelastic behavior was examined in a vacuum with a magnetically floating ball rheometer. This rheometer magnetically kept a position of a steel ball in a flowing liquid contained in a glass cell (test tubing) and measured a force acting on the ball, and the viscosity was obtained from this force. The viscoelastic relaxation after cessation of the flow was also detected as a decay of the force. In the experiment for the living PBLi2/Bz solution, the deactivation of the PB bianions was avoided by coating the steel ball with a nonreactive polyethylene film and by rinsing the cell with a Bz solution of diphenylethylenyllithium bef...

The local dynamics of 10 substituted polyacetylenes in the glassy state have been investigated using a quasielastic neutron scattering technique in a time range of picoseconds to several tens of picoseconds to see a relationship between the local mobility and the gas permeability of these polymers. Even in the glassy state, these polymers show quasielastic scattering components, suggesting that certain stochastic motions occur in the glassy state. The dynamic scattering laws S(Q,ω) of the quasielastic components were well fitted to the sum of two Lorentzians, i.e., the narrow (slow) and broad (fast) components. It was found that both the relaxation rate Γn and the fraction An of the narrow (slow) component show positive correlations with oxygen permeability coefficient (PO2), suggesting that the local mobility of the matrix polymers plays an important role in gas permeability. We then defined local flux F, which is the product of Γn and An, as a measure of the local mobility to find that F is proportional...

The intermolecular correlation due to electrostatic repulsion in flexible polyelectrolyte solutions as a function of ionic strength has been studied using small-angle neutron and X-ray scattering (SAXS and SANS) techniques. The ionic strength was changed by adding low molecular weight salts at a fixed polyion concentration (C = 0.25 mol/L). To solve the controversy about the added salt effect on the characteristic maximum in small-angle scattering of polyelectrolyte solutions, separation of the total scattering function into the intra- and intermolecular parts has been performed. With increasing the ionic strength of the solution the maximum position qm in the total scattering function of SAXS and SANS slightly shifts toward the lower scattering vector and subsequently disappears, whereas the maximum position in the intermolecular scattering function slightly shifts to the higher scattering vector, but the peak itself does not disappear even for the highest ionic strength of the present study though it be...

Rheological properties were examined for a butadiene−styrene (BS) diblock copolymer dissolved in an S-selective solvent, dibutyl phthalate (DBP). This copolymer was composed of a deuterated B block (MB = 13.3 × 103) and a protonated S block (MS = 53.9 × 103), and the microdomain structure in the quiescent state as well as under steady shear was detected with small-angle neutron scattering (SANS). At 25 °C, a quiescently equilibrated BS/DBP system of the BS concentration = 28 wt % exhibited elastic behavior under slow, small-amplitude oscillatory shear. This elasticity reflected a bcc lattice of BS micelles with B cores and S corona. Although the B cores were in the liquid state, the thermodynamic power of segregation from the S/DBP phase forced these cores to be arranged on the lattice at equilibrium. Under steady shear, the BS/DBP system exhibited significantly non-Newtonian flow behavior. At low shear rates (γ), the steady state was attained after a significant stress overshoot followed by a thixotropi...

Time-resolved light scattering measurements were performed on gelation processes of poly(vinyl alcohol) (PVA) solutions at 25 °C in mixtures of dimethyl sulfoxide (DMSO) and water (H2O) with volume ratios of 60/40 and 80/20. It was found that the scattering profile I(Q) from a 60/40 (DMSO/H2O) solution has a maximum whose position Qm is independent of time and that the intensity I(Q) at Q = Qm increases exponentially with time. These observations agree with the theoretical predictions for the initial stage of spinodal decomposition (SD) type phase separation, while the scattering profile I(Q) from a 80/20 solution has no peak. It is therefore concluded that the SD type microphase separation occurs before gelation in the 60/40 solution, but not in the 80/20 solution. On the basis of present, as well as past results, a possible mechanism of the gelation process for PVA solutions has been proposed.

Quasielastic neutron scattering experiments have been performed on polyisobutylene, trans-1,4-polychloroprene, and polyethylene in the energy range from 0.01 to 10 meV at temperatures far above the glass transition temperature T g and on cis-1,4-polybutadiene near Tg. Similar to the previously reported results on cis-1,4-polybutadiene far above T g , we observe in these polymers a slow process on a time scale from several tens to several hundreds of picoseconds which we term the E-process (or elementary process) as well as a fast process with a time scale of about a picosecond. We consider the relaxation time map of polybutadiene near and above the glass transition temperature to illustrate that the fast process is common for most glass-forming materials and that the E-process may be assigned to an elementary process involving local chain conformational transitions. Finally, we analyze the E-process in terms of a previously introduced jump diffusion model with damped vibrations, which is consistent with recent results of molecular dynamics simulations for bulk amorphous polymers, and we discuss the possible mechanism of the conformational transitions.

Aiming to clarify the mechanism of crystal nucleation of polymers, we have made a quantitative investigation about the conformational change of syndiotactic polystyrene (sPS) during the induction period (ca. 30 min) when crystallized at 120 °C, 25 K above the glass transition temperature Tg = 95 °C, from the glassy state, i.e., for the so-called glass crystallization by time-resolved Fourier transform infrared (FT−IR) spectroscopy. It was found that even in the induction period, the absorbance of trans conformation bands begins to increase and it continues to increase not only through the induction period but also after crystallization. This suggests that the length of rodlike segments consisting of trans sequences starts to increase in the induction period. In this connection, Doi's theory on the isotropic-to-nematic transition of polymer liquid crystals has predicted that the extension of these segments triggers the orientation fluctuations of the rod segments because the increase of their excluded volu...

Local chain dynamics of atactic polypropylene, a typical amorphous vinyl polymer, has been studied by both quasielastic neutron scattering and macroradical decay measurements by electron spin resonance to detect the fast process of picosecond order observed for most amorphous materials. It was found that the fast process sets in at the Vogel-Fulcher temperature T 0 , similar to observations for other simple polymers, suggesting that the fast process is a precursor of the glass transition. In coincidence with the onset of the fast process, the acceleration of the macroradical decay is also observed in the vicinity of T 0 , indicating a close connection of both phenomena. This is the first experimental evidence for the fast process from two independent measurements.

The complex strain-optical ratio, O*(ω), and the complex Young's modulus, E*(ω), of four vinyl polymers, atactic polypropylene, 1,2-polybutadiene, poly(ethylethylene), and poly(4-vinylbiphenyl), were measured from the rubbery plateau to the glassy zone to investigate the origin of the birefringence and the chain orientation in the glassy zone. The data, including those for polystyrene and poly(vinyl naphthalene), were analyzed through a modified stress-optical rule: The rule states that O*(ω) and E*(ω) are described as a sum of two component functions (denoted by R and G) and that a proportional rule similar to the ordinary stress-optical rule holds well for each of the R and G components with different stress-optical coefficients. The R and G components have been interpreted to be respectively related to the orientation of the main chain axis toward the stretch direction and tilting of the structural units by a rotational orientation about the main chain axis. According to this interpretation, the stres...

The effect of long-range density fluctuations on the primary (α-) relaxation in poly(methyl-p-tolylsiloxane) (PMpTS) was studied by means of light scattering. It is shown that the long-range density fluctuations (clusters) contribute only to the polarized (VV) and not to the depolarized (VH) correlation functions and make the system apparently nonergodic in the time scale of the α-process. Samples with different amounts of clusters were obtained by annealing at 55 °C for different time intervals in temperature jump experiments : +120 → +55 → -2.6 °C. The mean relaxation times and their distribution of the α-process obtained from the VH correlation functions (sample with clusters) and both VV and VH correlation functions (cluster-free sample) were equal and did not depend on the amount of clusters, indicating no coupling between the long-range density fluctuations and the primary α-relaxation.

The authors report small-angle neutron scattering (SANS) and light scattering (LS) studies on poly(vinyl alcohol) (PVA) gels formed in a mixture of deuterated dimethyl sulfoxide (DMSO-d{sub 6}) and heavy water at 23 C. It was reported in a previous paper that the SANS intensity I(Q) of the PVA gels is well described by the Ornstein-Zernike (OZ) formula I(0)/(1 + {zeta}{sup 2}Q{sup 2}) and Porod`s law Q{sup {minus}4} for 0.01 {angstrom}{sup {minus}1} < Q < 0.035 {angstrom}{sup {minus}1} and 0.05 {angstrom}{sup {minus}1} < Q < 0.1 {angstrom}{sup {minus}1}, respectively. In this work, the authors extended the Q range down to 3 {times} 10{sup {minus}3} {angstrom}{sup {minus}1} and found that I(Q) turns up for Q < 8 {times} 10{sup {minus}3} {angstrom}{sup {minus}1} to deviate from the OZ formula. This upturn has been assigned to structure due to phase separation based on the results of SANS and LS measurements. In order to investigate the gelation process, time-resolved SANS measurements were carried out on the PVA solutions after quenching to 23 C from 100 C. It was found that the correlation length {zeta} evaluated by the OZ formula in a Q range of 0.01--0.035 {angstrom}{sup {minus}1} is dominated by concentration fluctuations in the earlymore » stage of the gelation before crystallization (t < 200 min) while, after the crystallization initiates, the average correlation distance between the nearest-neighboring crystallites becomes a dominant factor in {zeta}. Distance distribution function P(r) which is defined by inverse Fourier transformation of the scattering intensity was calculated to see the size and the distribution of the crystallites.« less

On the basis of a new finding reported in previous studies that the structural formation in the induction period of crystallization involves a kind of phase separation of spinodal decomposition due to the orientation fluctuations of polymer segments, we have investigated the structural change of PET from a structure size point of view using a SAXS technique when it was crystallized at 80 or 5°C above the T g from a melt-quenched glass. A spatial density correlation analysis of the SAXS intensities reveals that the size of the dense domains caused by the density fluctuations in the induction period is fairly large compared with the lamellar thickness after crystallization, indicating that these dense domains are not the embryos predicted by the classic nucleation theory

The structure of poly(vinyl alcohol) (PVA) gels formed in a mixture of deuterated DMSO and heavy water at 23°C has been investigated. It was directly confirmed from the wide-angle neutron scattering measurements that cross-linking points or junction points in the gels are crystallites. In the small-angle scattering measurements, it was found that the scattering intensity I(Q) decreases with Q according to the -4th power law (Porod's law) in the Q range above 0.05 A -1 where Q=4π sin θ/λ (2θ and λ are scattering angle and wavelength of neutron, respectively), suggesting that the surface of the crystallites has a clear boundary

Local motions are investigated in the time range 10 −13 to 10 −10 s. Two modes are found in this time range. The faster and slower modes are assigned to damped vibrational motion and local conformational transition, respectively. The latter is analyzed in terms of a jump diffusion model with the damped vibrational motions on the jump sites. The observed conformational transition rate is compared with the Kramers' rate theory, and the spatial scales of the motions are discussed based on the molecular structure of cis-1,4-polybutadiene

Etude de solutions de polyhydrogenesulfate de vinyle et de ses sels de lithium, sodium et potassium

La transition entre la region diluee et la region semidiluee se produit a une masse moleculaire critique. Etude avec du polystyrenesulfonate de sodium sans addition de sel