We have studied the growth dynamics of domains on ternary fluid vesicles composed of saturated (dipalmitoylphosphatidylcholine), unsaturated (dioleoylphosphatidylcholine) phosphatidylcholine lipids, and cholesterol using a fluorescence microscopy. The domain coarsening processes are classified into two types: normal coarsening and trapped coarsening. For the normal coarsening, the domains having flat circular shape grow in a diffusion-and-coalescence manner and phenomenologically the mean size grows as a power law of approximately t(2/3). The observed growth law is not described by a two-dimensional diffusion-and-coalescence growth mechanism following the Saffman and Delbrück theory, which may originate from the two-body hydrodynamic interactions between domains. For trapped coarsening, on the other hand, the domain coarsening is suppressed at a certain domain size because the repulsive interdomain interactions obstruct the coalescence of domains. The two-color imaging of the trapped domains reveals that the repulsive interactions are induced by the budding of domains. The model free energy consisting of the bending energy of domains, the bending energy of matrix, the line energy of domain boundary, and the translation energy of domains can describe the observed trapped coarsening. The trapping of domains is caused by the coupling between the phase separation and the membrane elasticity under the incompressibility constraint.
We report in situ nanostructures and dynamics of polybutadiene (PB) chains bound to carbon black (CB) fillers (the so-called "bound polymer layer (BPL)") in a good solvent. The BPL on the CB fillers was extracted by solvent leaching of a CB-filled PB compound and subsequently dispersed in deuterated toluene to label the BPL for small-angle neutron scattering and neutron spin echo techniques. The results demonstrate that the BPL is composed of two regions regardless of molecular weights of PB: the inner unswollen region of ≈ 0.5 nm thick and outer swollen region where the polymer chains display a parabolic profile with a diffuse tail. In addition, the results show that the dynamics of the swollen bound chains can be explained by the so-called "breathing mode" and is generalized with the thickness of the swollen BPL. P olymer nanocomposites have been of great interest to the broad materials community for at least the last three decades. 1 The addition of nanoparticles to polymers affects the overall rheological and mechanical properties mainly due to the creation of a "bound polymer layer (BPL)" on a particle surface. 2−10 The most thorough experimental and theoretical studies on BPLs have been carried out on carbon black (CB)-filled rubber systems 11−16 used for automobile tires. A nanometer-thick BPL is typically formed on the CB surfaces and is resistant to dissolution even in a good solvent. 17 In theory, the interactions between polymers and particle surfaces restrict a molecular motion which correlates with increased resistance to mechanical deformation as compared to free polymers that locate away from the particle surface. 18 This restricted chain motion was indicative in various polymer nanocomposites by nuclear magnetic resonance (NMR) spectroscopy experiments. [5][6][7][8]19,20 In addition, the existence of an "interphase" with the property between those of the BPL and the bulk has been hypothesized as the origin of long-range propagations of the effects of the BPL. 21−25 However, it is challenging to distinguish the bound polymer chains or the interphase from the bulk experimentally, because they are all composed of the same component. 25,26 Hence, a molecular scale description of real conformations of the bound polymer chains, which is crucial for a better understanding of the reinforcement mechanism at the interface, remains unclear. 7,27 To overcome this difficulty and provide detailed nanometerscale descriptions at the polymer/filler interface, we use smallangle neutron scattering (SANS) and neutron spin echo (NSE). In addition, we use simplified industrial polybutadiene (PB)/CB nanocomposites as a model. A novel aspect of CB along with its practical importance is the scattering length density that is nearly identical to those of deuterated solvents or polymers, allowing "contrast matching" neutron scattering experiments 28 to gain information about the bound polymer chains selectively. Furthermore, as will be discussed later, the PB bound layer on the CB filler can be considered as a "slab" config...
We report the in situ structures and dynamics of hydrogenated polybutadiene (PB) chains bound to carbon black nanoparticle surfaces in polymer solutions composed of deuterated PB and deuterated toluene using small-angle neutron scattering and neutron spin-echo techniques together with molecular dynamics (MD) simulations. The experimental results showed that the swollen bound polymer chains exhibit the collective dynamics (the so-called breathing mode) at polymer concentrations (c) below and above the overlap polymer concentration (c*) (i.e., 0.61 < c/c* < 1.83), where the concentration profiles of the bound polymer remained unchanged with the different c values. Interestingly, the collective dynamics slowed down by a factor of 2 compared to that in pure d-toluene when the chain lengths of the bound polymer and matrix polymer were equal. However, when the free polymer chains were longer than the bound polymer chains, the decrease in collective dynamics was not as significant. MD simulations were performed to explore the interfacial event as a whole. As a result, we found that the matrix polymer chains, whose length is equal to that of the bound polymer, can be accommodated in the bound polymer layer effectively and are “strangulated” by the bound polymer chains, while the longer matrix polymer chains only partly penetrate into the bound chains and the diffusion behavior was hardly affected compared to that in bulk.
For rapid charging of lithium-ion batteries, a series of novel electrode-active materials have been studied. However, those materials suffered from replacing conventional metal oxides, such as LiCoO2 and LiFePO4, because of the strict performance criteria for commercialization. As an alternative approach, we propose the hybridization of the conventional inorganic active materials with organic redox-active polymers which are characterized by fast electrode kinetics. A new robust organic-radical-substituted polyether was synthesized to yield one of the highest charge transportabilities of nonconjugated polymers with a charge diffusion coefficient of 10–7 cm2/s. The hybrid electrode of LiFePO4 and a small amount of the polymer was able to be charged within several minutes by virtue of the electrocatalytic oxidation of the metal oxide with the radical polymer. In addition, several 4 V class organic redox-active polymers were synthesized for the hybrid with LiCoO2. After hybridization, the LiCoO2 electrodes could also be charged within several minutes with the reduced overvoltages.
We have investigated the effects of grafted polymer chains [poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)] on the bending modulus and the intermembrane interactions of lamellar membranes (C(12)E(5) water) by means of a neutron spin-echo and a small-angle x-ray scattering technique. In this study the hydrophilic chain takes the mushroom configuration on the membrane. The bending modulus of the polymer-grafted membranes increases in proportion to the square of the end to end distance of the polymer chain, which agrees well with the theoretical prediction of Hiergeist and Lipowsky [J. Phys. II 6, 1465 (1996)]. From the interlamellar interaction point of view, the mushroom layer is renormalized to the membrane thickness, which enhances the repulsive Helfrich interaction. When the size of the decorated polymer chain increases to the interlamellar distance, however, the mushroom is squeezed so as to optimize the interlamellar potential. Further increase of the grafted polymer size brings a lamellar-lamellar phase separation, where the grafted polymer chains are localized in the dilute lamellar phase and the concentrated lamellar phase forms the onionlike texture.
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