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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.
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.
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.
We developed 2,5-furanylene sulfide-containing polymers bearing different spacers as repeating units and evaluated the interactions between the furanylene sulfide units in the polymer. Treatment of a 2,5-dichlorofuran derivative with dithiolates at 200 °C promotes polycondensation via nucleophilic aromatic substitution to give the corresponding furanylene sulfide-containing polymers. Through tensile measurements and spectral analyses, it was found that the furanylene sulfide moieties form remarkably stable π–π stacking structures based on the enhanced dipole moment induced by sulfur linkages. When the polymer has a long spacer between repeating furanylene sulfide units, the polymer behaves as a chemically stable network polymer comprised of π–π stacking structures as cross-linking units.
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.
Epoxy resins, which are obtained by the curing reaction of epoxy- and amine-compounds mixture, have been often utilized in contact with metals. We herein report on the chemical composition of the epoxy resin in close proximity to the copper interface on the basis of a non-destructive method. The concentration of the amine component in the interfacial region was 2-fold higher than that in the bulk, and the interfacial enrichment extended over at least 10 nm.
The synthesis of carboxylated IIR was achieved in high yield starting from brominated substrates, which were first converted to azides and used in the copper-catalyzed azide–alkyne Huisgen cycloaddition reaction with acetylenic acids containing different aliphatic spacer lengths. Optimization of the reaction conditions was critical to avoid the formation of gel particles in the reactions and to achieve full conversion of the bromide to carboxylate derivatives.
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.
Poly(methyl methacrylate) smart xerogels (PAsp-xgs) crosslinked by polyaspartate side chains were synthesized and the effects of the polyaspartate helix-sense inversion on their properties were investigated. PAsp-xg was found to irreversibly shrink to a volume ratio of 0.7 when heated to ~393 K. The volume shrinkage was suggested to be induced by the helix-sense inversion of the polyaspartates in the hybrid xerogels.
Solvent-free base-catalyzed CO2 fixation into polymers having 2-pyridyl group-substituted propargylamine moieties in the main and side chains was achieved under atmospheric CO2 condition. The reactivity of the polymer films was improved by the introduction of pendant tertiary amine moiety.
Ethylene polymerization with bis(diethylamido){di(3-methylindol-2-yl)phenylmethane}titanium (1) was examined using modified methylaluminoxane (MMAO) as an activator. The activity of the 1/MMAO catalyst system was low (16.3 kg of polyethylene (PE)/mol of Ti•h), but pretreatment of 1 with ClSiMe3 followed by activation with MMAO improved the activity up to 154 kg of PE/mol of Ti•h. The obtained PEs are all monomodal by size exclusion chromatography and have linear structures by NMR spectroscopy. The 1/ClSiMe3/MMAO catalyst system was also active for ethylene/1-octene copolymerization (90 kg of copolymer/mol of Ti•h).
Irrespective of the degree of polymerization, the molecular mobilities of the 2-hydroxyethyl methacrylate (HEMA) moieties are smaller than those of the 2-methoxyethyl acrylate (MEA) moieties. Preventing the polar functional groups of the foulants and materials from forming a hydrogen-bonding network is important to enhance the mobilities of the molecular chains of non-ionic polymeric materials. We speculate that enhancing the mobilities of the molecular chains is key to improving blood compatibility.
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 effect of trialkylaluminium compound (AlR3, where R = Me, Et, iBu) addition on the performance of the transition metal complex/AliBu3/Ph3CB(C6F5)4 catalysts in ethylene/1-olefin copolymerization was investigated. It was shown that AlR3 may affect the catalytic properties of the system (activity, comonomer incorporation, and copolymer microstructure). This influence is dependent on the type of organoaluminum compound and on the structure of the complex, i.e., on the structure of the ligand and on the type of transition metal.
Taking advantage of the flexible movement for the benzotriazole in the side chains, the resulting membranes exhibit encouraging proton conductivities and fuel cell performance.
The adhesion force between the tentacle of a live cypris and polymer brushes on the sidewall of cover glass was directly measured by scanning probe microscopy in seawater. The cypris was immobilized on the cantilever with glue, and then forced to make contact with the modified surface. When the tentacle was detached by moving the cantilever away from the surface, the torsion of the cantilever caused the laser deflection on the photodiode corresponding to the adhesion force. Polymer brush surfaces exhibited extremely low adhesion to the cypris larva.
Conjugated polymers of diketopyrrolopyrrole (DPP) and thiophene, especially 2,5-di-2-thienyl-thieno[3,2-b]thiophene, were characterized by their molecular packing orientation with a π-π stacking distance of 3.6 Å and a high field-effect hole mobility on the order of 10−2 cm2/Vs. A perovskite solar cell, fabricated with the genuine or both oxidizing and salt dopant-free polymer as a hole-transporting layer, displayed a high photo-conversion efficiency of 16.3% with high durability.
The friction properties of a dilute solution of block copolymer additives in a base lubricant oil confined between mica surfaces were investigated using the surface forces apparatus. Friction force, sliding film thickness, and contact geometry were evaluated in detail, and the results were compared to those of the solutions of a different block copolymer additive having similar molecular structure. The relationship between the chemical structure of additives, confined structures between surfaces, and friction mechanisms were discussed, which shed new light of the design of low-friction surfaces in oil-based lubrication.
Highly porous organic structures are synthesized by the oxidative polymerization of pyrrole derivatives in a concentrated monomer and oxidant solution. The rapid polymerization of pyrrole derivatives by oxidation with FeCl3 in CHCl3 as a cosolvent for the monomer and the oxidant leads to nanometer-scale branching morphologies that have a specific surface area of ~900 m2 g−1 with bimodal pore-size distribution.
