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Self-organization in nonequilibrium systems composed of a bulk filler powder and a bulk polymer melt as an initial state (i) into a final ordered state (f) in applied mechanical field occurs via cascade evolution of the dissipative structures (a) to (e) accompanied by the cascade energy dissipation processes [Process (I) and Process (II)]. These processes also induce the relevant cascade changes in free energy and stress level.
Designer supramolecular polymers are a growing field of polymer materials. The designability and flexibility in their structures and functionality have attracted a great deal of attention in polymer science, as well as in supramolecular chemistry. These polymeric structures are formed from one or more molecular components via reversible bonds; therefore, monomeric and polymeric states are in equilibrium on the relevant experimental timescale. The dynamic nature of supramolecular polymers in terms of chain lifetime and conformational flexibility are determined by external conditions. This adaptivity can result in stimuli-responsive structures and properties. This article describes the use of our host–guest structures based on a calix[5]arene, a bisporphyrin, and a self-assembled capsule in the synthesis of supramolecular polymers.
Conducting polymers were synthesized via in situ polymerization, using nanoclay bentonite sodium and its modified form. The polymer nanoclay modified form showed enhanced solubility compared to the original polymers and improved thermal stability, along with higher corrosion inhibition efficiency and aggregation-induced emission with luminescence dependent on the aggregate structure.
The network structure evolution of a hexamethylenetetramine-cured novolac-type phenolic resin was investigated using 1H-pulse NMR spectroscopy, SAXS and WAXS to elucidate the mechanism responsible for the apparent absence of inhomogeneity after curing, in which the inhomogeneity was first observed at the gel point.
Changes in the aggregated structure of silica in styrene–butadiene rubber are measured with small-angle X-ray scattering under cyclic uniaxial elongation. We employ a spherical harmonics expansion approach to quantitatively analyze the anisotropic scattering data and to separate the anisotropic response of the silica’s configuration upon the elongation from the isotropic component. This study demonstrates that the combination of time-resolved small-angle scattering measurement and an analysis using spherical harmonics expansion is quite useful for exploring the structural response of filled rubber systems to an external deformation.
We investigated the crystallization dynamics of P3MB1 under isothermal condition by synchrotron radiation X-ray scattering and optical microscopy. At a crystallization temperature (Tc) of 297 °C, needle-like crystals consisting of stacked lamellae formed. As Tc increased, the number of lamellar branches decreased and morphological transition (spherulite → axialite → needle-like crystal) occurred. The suppression of lamellar branching was attributed to the low viscosity of the molten portion at Tc.
Grazing incidence wide-angle X-ray diffraction study of lamellar orientation in isotactic polypropylene thin films. Crystalline structure of isotactic polypropylene (iPP) thin films was investigated by means of grazing incident wide-angle X-ray diffraction, atomic force microscopy, and transmission electron microscopy. Flat-on mother lamellae with orthogonal daughter lamellae form in the thin film. We propose a lamellar growth model for iPP thin films in which the crystallization progresses flat-on mother lamellae at the substrate interface to out-of-plane growth of daughter lamellae from the mother lamellae.
Thermal behavior, molecular aggregation structure, and water repellency of a comb-shaped fluoropolymer, poly{2-[(perfluorooctylethyl)carbamate]ethyl}acrylate (PFAUr-C8), were investigated. PFAUr-C8 exhibited polymorphic ordered structures, where the stacked lamellar structure of Rf side chains was maintained without their lateral translational order. The cohesive dipolar interactions in the carbamate linkers would induce the thermal stability of the lamellar structure. PFAUr-C8 exhibits superior water repellency.
Time-resolved synchrotron small- and wide-angle X-ray scattering was carried out during the high-speed elongation of unoriented exclusively β-crystal-containing isotactic polypropylene. In the first stage, microvoid formation started. In the second stage, separation of crystalline block, unfolding, and withdrawing of the crystalline chains were occurred. And then the β–α transformation produced a highly oriented α-crystal parallel to the elongation direction. In the third stage, lamellae underwent inter- and intralamellar slipping and fragmentation and then unfolded to produce the oriented α-crystal.
The change of ultra-small-angle X-ray scattering (USAXS) image after necking was taken for poly(ethylene terephthalate) (PET) and poly(phenylene sulfide) (PPS) fibers. USAXS pattern of PPS shows three streaks, which were meridional and equatorial streaks and total reflection. In addition to the three streaks observed for PPS, USAXS pattern of PET shows a layer-lined streak. Far stronger meridional streak of PPS means the periodic density deviation preliminary formed in the as-spun fiber, and the layer-lined USAXS streak of PET could be explained by the periodic bundle of a fibrillar-shaped smectic phase.
The role of strain rate (\(\dot \varepsilon\)) in strain induced crystallization (SIC) of vulcanized natural rubber (NR) and synthetic isoprene rubber (IR) was studied by in-situ wide angle X-ray scattering (WAXS). The nucleation rate (I) was determined by measuring the slope on the plot of the scattering intensity (IX) as a function of time (t). Various I values were determined for various \(\dot \varepsilon\). On the plot of I vs. \(\dot \varepsilon\), we found that I is proportional to \(\dot \varepsilon\); I∝\(\dot \varepsilon\)
Time-resolved X-ray measurements during melting and analyses of samples heat treated near their melting temperature revealed a structural change of the melt-crystallized isotactic polypropylene. During melting at a heating rate of 5 K/min, we observed the appearance of a higher melting temperature peak due to lamellar thickening of the α1 crystal. Lamellar thickening was accompanied by an increase in central diffuse scattering of SAXS, suggesting that thickening occurred at random positions and caused disordering of lamellar stacking.
Isothermal crystallization of poly(glycolic acid) (PGA) was carried out using terahertz (THz) and infrared (IR) spectroscopy and simultaneous small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) measurements. The intensity of the absorption peak at 192 cm−1 increased before the increase in intensity of the peak at 65 cm−1 during the isothermal melt-crystallization process at 185 °C. This is due to a difference in the vibrational origins of these two bands. In addition, these THz bands appeared after the appearance of the SAXS and WAXD peaks
A poly(4-methylpentene-1) (P4MP1) film was prepared on a quartz substrate, which was a model system of interfaces in a filler-reinforced semicrystalline polymer composite. Grazing-incidence wide-angle X-ray diffraction measurements revealed that P4MP1 in the film after the isothermal crystallization formed a Form I crystal polymorph, in which the chain axis was oriented along the direction parallel to the quartz interface. Combining sum-frequency generation vibrational spectroscopy with molecular dynamics simulation enabled us to study the local conformation of P4MP1 chains at the quartz interface and the changes that occurred with isothermal crystallization.
We crosslinked polythiophenes with disiloxane groups in its side chains by dicumyl peroxide. The crosslinked polythiophenes maintained low glass transition temperatures and low Young’s modulus, while they emerged high elastic recoveries. Moreover, as the concentration of dicumyl peroxide increased, the crosslinked polythiophenes possessed higher elastic recoveries. We obtained completely elastic semiconductive polythiophenes.
Polythiourethane (PTU) elastomers, which are obtained by the reaction between polyol, diisocyanate, and dithiol, are expected to have some properties that polyurethanes (PUs) do not have. Herein, the microphase-separated structure and mechanical properties of the 1,4-bis(isocyanatomethyl) cyclohexane-based PTUs were investigated. It was revealed from the differential scanning calorimetry, small-angle X-ray scattering and dynamic viscoelasticity measurements that the PTUs possess a stronger degree of microphase separation and lower glass transition temperature of soft segment compared to that of PUs.
The dispersion state and aggregate structure of carbon black in polystyrene composites prepared by solvent casting suspensions in different dispersion media with different particle contents and their effects on the bulk rheological properties of the composites were investigated by transmission electron microscopy, ultrasmall-angle and small-angle X-ray scattering, and dynamic viscoelasticity measurements. The viscoelastic moduli of the melt polymer composites below and above the percolation limit varied with the dispersion medium, reflecting the difference in the macroscopic dispersion state and aggregate structure of carbon black in polystyrene.
The clear experimental results are revealed to confirm that a special type of a diluent can act as an agent of improving the crystallizability of poly(L-lactide) (PLLA). We conducted time-resolved SWAXS to follow the isothermal crystallization of PLLA. The WAXS result shows enhancing effects of the diluent on the crystallization of PLLA such as reducing induction period and accelerating crystallization. The growth of the crystalline lamellae in their thickness direction and the space filling by the stacks of crystalline lamellae are found to be accelerated in the presence of the diluent.
