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The coagulation size of freezable water in a poly(vinyl alcohol) (PVA) hydrogel was investigated as a function of the freeze/thaw cycle period using thermal analysis. For longer cycle periods, the coagulation size was larger.
Rod-like capsules consisting of a thin crosslinked poly(vinyl acetate) (PVAc) shell and a calcium carbonate core were synthesized by suspension polymerization technique. The shell thickness ranged from 12 to 19 nm. The glass transition temperature Tg of the filled shell was revealed to be raised, whereas the dynamic length scale ξ(Tg) to be lowered from the bulk values. The Tg shift may be partly attributed to unstable configuration that is retained by the crosslink.
Two different strategies have been successfully used to modulate the swelling capacity of thermo-responsive hydrogels based on 2-(2-methoxyethoxy)ethyl methacrylate: (1) controlling the crosslinking degree from varying the crosslinker type and amount, and (2) using N-isopropylacrylamide as comonomer, which in addition allows to modulate the volume and glass transition temperatures.
Reversible inclusion complexation between size-mismatched components, poly(ethylene glycol) (PEG) and β-cyclodextrin (β-CD), is described. A PEG chain with proper end groups allowed β-CD to be trapped onto the chain, and multitopic β-CD derivatives to crosslink the chain supramolecularly. The supramolecular crosslinking formed only when the system was heated, and dissociated by dilution and shaking without reheating.
This paper discusses an effective route in the graft copolymerization of methyl methacrylate monomer onto syndiotactic polystyrene (sPS) using free-radical polymerization, and the effect of an organophilic montmorillonite (O-MMT) on the final properties of the graft copolymer sample. The structure of vinyl-terminated sPS multicenter macromonomer and the graft copolymer were characterized by means of Fourier transform infrared and 1H nuclear magnetic resonance spectroscopy. The exfoliated sPS-graft-poly(methyl methacrylate)/MMT nanocomposite was characterized by means of X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and differential scanning calorimetry.
Polyrotaxane networks were synthesized by exploiting a Pd-templated bis-macrocycle as a topological cross-linker during radical polymerization. Radical polymerization of 4-vinylpyridine with the topological cross-linker in the presence of a catalytic amount of AIBN gave the network polymer as a gel. The addition of 4-tert-butylstyrene as a vinyl co-monomer to the polymerization system afforded a sufficiently stable gel as the polyrotaxane network, enabling the introduction of stopper moieties into the trunk polymer.
Bio-based thermosetting resins, biseugenyl succinate (BEUS) and bis(4-maleimidephenyl) succinate (BMIS) were synthesized from succinic acid and eugenol. The BEUS/BMIS cured at 230 °C for 1 h showed a higher glass transition temperature and a greater tensile strength than 2,2′-diallyl bisphenol A (DABA)/4,4′-bismaleimidediphenylmethane (BMIM) cured under the same condition. The Fourier Transform Infrared (FTIR) analysis of the cured materials revealed that chain polymerization of allyl and maleimide groups occurred to produce BEUS/BMIS, whereas a stepwise ene reaction and subsequent chain polymerization in addition to an etherification reaction occurred to produce DABA/BMIM.
Photo-stimulated luminescence spectra (PSLS) emission from alumina-filled epoxy nanocomposites consisting of varying volume fractions of alumina nanoparticles was collected and analyzed to characterize dispersion within the sample through intensity maps. The measurements are based on integrated intensity data from the R1 curve of α-alumina throughout each specimen. This novel method has potential as a quality control method to determine the location of voids, inclusions and/or agglomerations, while in addition predicting the volume percentage of particles within a specimen.
Our study explored microstructures at skin, sub-skin and core zones of injection-molded carbon black particles/polypropylene composite. Figure 3 in the paper showed the schematic map on definition of each zone. We found that strong oriented microstructure was formed at core instead of at sub-skin, especially under lower packing pressure. A band with non-continuous conductive path was found under the action of higher injection process, and it will expand with lowering packing pressure.
Polymer nanoparticles (PNPs) that consist of a low-bandgap conjugated polymer, co-poly(2,3-diphenylthieno[3,4-b]pyrazine-alt-9,9-dioctylfluorene), were prepared for the photoluminescence in vivo imaging in the near infrared region. The emission efficiency was enhanced by the fluorescent resonance energy transfer from the conjugated polymer to a silicon naphthalocyanine dye. The dye-doped conjugated PNPs enabled the bright fluorescence imaging of live mice.
Here, we show that a sulfonated polyaramide exhibiting a lyotropic liquid-crystalline phase in aqueous solution gives optically active films through spin-coating, and that their chiral handedness can be tuned using the rotational direction. We further suggest that hydrogen-bond formation between polymer backbones have a key role in inducing selective chiral signs.
