Effect of conformation of interfacial adsorbed chains on physical aging of polymer nanocomposites.

The dynamics of polymer nanocomposites varies depending on the physics and chemistry at the polymer-nanoparticle interface. The physical aging of the nanocomposites is accelerated or retarded based on interfacial interactions and the state of polymer adsorption at the interfaces. In this study, we investigated the aging kinetics of silica-polystyrene nanocomposites using differential scanning calorimetry, focusing on the effect of local conformations of chains adsorbed on the nanofiller surface. The results show that the temperature dependence of the aging rate follows a Vogel-Fulcher-Tammann relationship at high temperatures, whereas it exhibits an Arrhenius-like behavior below a characteristic temperature (Tc). Notably, at T < Tc, the aging rate decreases with increasing loop height of the chains adsorbed on the filler surface, but the activation energy remains unchanged. We proposed that the suppression of the aging rate at T < Tc is likely related to an increase in the length scale over which the slow interfacial dynamics can propagate due to the increased topological interactions between the chain loops of a larger size and the free chains in the matrix. The increased packing frustration occurring at the filler surface occupied by the larger loops might also contribute to the decreased aging rate.

Length Scale of Molecular Motions Governing Glass Equilibration in Hyperquenched and Slow-Cooled Polystyrene.

Polymer glasses attain thermodynamic equilibrium owing to structural relaxation at various length scales. Herein, calorimetry experiments were conducted to trace the macroscopic relaxation of slow-cooled (SC) and hyperquenched (HQ) polystyrene (PS) glasses and based on detailed comparisons with molecular dynamics probed by dye reorientation, we discussed the possible molecular process governing the equilibration of PS glasses near the glass transition temperatures (Tg). Both SC and HQ glasses equilibrate owing to the cooperative segment motion above a characteristic temperature (Tc) slightly lower than the Tg. In contrast, below the Tc, the localized backbone motion with an apparent activation energy of 290 ± 20 kJ/mol, involving approximately six repeating units, assists equilibrium recovery of PS glasses on the experimentally accessible time scales. The results possibly indicate the presence of an alternative mechanism other than the α-cooperative process controlling physical aging of materials in their deep glassy states.

Carbon skeleton materials derived from rare earth phthalocyanines (MPcs) (M = Yb, La) used as high performance anode materials for lithium-ion batteries.

In this work, novel carbon skeleton materials were prepared by high-temperature carbonization of rare earth phthalocyanines (MPcs) (M = Yb, La) under a nitrogen atmosphere. The resulting carbon materials of YbPc-900 (carbonisation temperature of 900 °C for 2 h) and LaPc-1000 (carbonization temperature of 1000 °C for 2 h) have a graphite-layered structure in predominantly ordered states, with a smaller particle size, a larger specific surface area and a higher degree of hard carbonization compared to those of the uncarbonized sample. As a result, the batteries using the YbPc-900 and LaPc-1000 carbon skeleton materials as electrodes display excellent energy storage behaviors. The initial capacities of the YbPc-900 and LaPc-1000 electrodes at 0.05 A g-1 were 1100 and 850 mA h g-1, respectively. After 245 cycles and 223 cycles, the capacities remain at 780 and 716 mA h g-1 with retention ratios of 71% and 84%. At a high rate of 1.0 A g-1, the initial capacities of the YbPc-900 and LaPc-1000 electrodes were 400 and 520 mA h g-1, respectively, and after 300 cycles, the capacities can still remain at 526 and 587 mA h g-1 with retention ratios of 131.5% and 112.8%, respectively, which were much higher than those of the pristine rare earth phthalocyanine (MPc) (M = Yb, La) electrodes. Moreover, better rate capabilities were also observed during the YbPc-900 and LaPc-1000 electrode tests. The capacities of the YbPc-900 electrode at 0.05, 0.1, 0.2, 0.5, 1 and 2C were 520, 450, 407, 350, 300 and 260 mA h g-1 respectively, which were higher than those of the YbPc electrode (550, 450, 330, 150, 90 and 40 mA h g-1). Similarly, the rate performance of the LaPc-1000 electrode at different rates was also significantly improved compared to that of the pristine LaPc electrode. In addition, the initial Coulomb efficiencies of the YbPc-900 and LaPc-1000 electrodes were also greatly improved compared to those of pristine YbPc and LaPc electrodes. After carbonization, the YbPc-900 and LaPc-1000 carbon skeleton materials derived from rare earth phthalocyanines (MPcs) (M = Yb, La) exhibit improved energy storage behaviors, which would provide new ideas for developing novel organic carbon skeleton negative materials for lithium ion batteries.

Botulinum Toxin A Alleviates Persistent Erythema and Flushing in Patients with Erythema Telangiectasia Rosacea.

INTRODUCTION: The persistent erythema and flushing seen in some cases of rosacea do not respond effectively to, or may easily relapse after, oral medication or light-based therapies (laser or intense pulsed light). Intradermal botulinum toxin A (BTX-A) injection can be used to treat intractable erythema and flushing, but studies with large samples and long-term observation have not been conducted to determine its effectiveness and safety. The aim of this study is thus to investigate the effective duration and safety of intradermal BTX-A injection for intractable erythema and flushing. METHODS: Sixteen patients with rosacea with erythema telangiectasia were injected with BTX-A at 1-cm intervals between each point. Clinician Erythema Assessment (CEA) scores were obtained at baseline and 1 month after injection. Flushing assessment and survey using the Dermatological Quality of Life Index (DLQI) questionnaire were conducted at baseline and at 1, 3, and 6 months after injection. RESULTS: At 1 month after injection, CEA scores revealed significant improvements in erythema and flushing; the results of the questionnaire on flushing and DLQI indicated that the improvement of flushing usually lasted for 3-6 months, but the effect decreased significantly at 6 months, and individual patients needed another treatment. CONCLUSIONS: BTX-A significantly improves the symptoms and quality of life of patients with refractory rosacea with few adverse effects.

Linear Alternating Associative Polymer with Ultrahigh Molecular Weight: Facile Preparation by Self-Assembly Assisted Dimerization of Anthracene and Rheology in Aqueous Solution.

Alternating associative polymers (AAPs) containing more than two species of alternating hydrophobic and hydrophilic units can form unique physical network and perform interesting rheological behavior in aqueous solution. In this work, an AAP was prepared through self-assembly assisted dimerization of an anthracene-functionalized telechelic associative polymer (AnTAP) in aqueous solution by light irradiation. It is demonstrated that AnTAP can in situ chain extend to AAP with well-defined linear structure and ultrahigh molecular weight through dimerization reaction of anthracene moieties in the core of micelle under light irradiation. Meanwhile, the solution changes from viscoelastic liquid to a free-standing gel, because a physical network that cannot relax in a finite time window has developed along with the dimerization process. The results are therefore of interest not only for understanding the network structure and rheological properties of AAP solution, but also for preparing AAPs with ultrahigh molecular weight by self-assembly assisted photodimerization reactions.