Main-Side Chain Hydrogen Bonding-Based Self-Healable Polyurethane with Highly Stretchable, Excellent Mechanical Properties for Self-Healing Acid-Base Resistant Coating.

Developing an autonomous self-healing polyurethane (PU) elastomer with excellent mechanical properties and high ductility has attracted increasing attention. Nowadays, the synthesis of elastomers with excellent mechanical properties and rapid self-healing at room temperature faces a huge challenge. Herein, This work reports a new supramolecular PU with excellent mechanical properties and rapid self-healing at room temperature through the introduction of T-type chain extender into the supramolecular polymer chain. The introduction of T-chain extender can be used to enhance the mechanical strength of PU, and the multiple hydrogen bonds on the side-chain provide theoretical support for the rapid self-healing ability of PU. Maximum stress of the synthesized PU can reach 3.4 ± 0.15 Mpa, and maximum elongation at break can reach 3200% ± 160%. Due to flexibility and re-constructability of side-chain hydrogen bonds, PU stress repair efficiency can reach 96.7%, and can be self-healing scratches rapidly and effectively at room temperature. The mechanical properties and self-healing properties of PU can be adjusted by the content of T-type chain extender. The PU is applied to the metal surface coating, which has excellent acid-base resistance, bond strength up to 2.9 ± 0.1 Mpa, and the ability to eliminate local damage on the coating surface quickly at room temperature.

A new insight into the thermodynamical criterion for the preparation of semiconductor and metal nanocrystals using a polymerized complexing method.

This work reports the intrinsic thermodynamical criterion for the preparation of metal and semiconductor nanocrystals using a polymerized complexing method. The basic principle of this method is the formation of a polymerized complexing structure between mono-, binary-, or ternary-metallic ions and bonding agents in aqueous or ethylene glycol solutions by evaporation of the solvents. Heat treatment of the complexing structure under N2 atmosphere produces H2 and CH4 gases, which can reduce the oxide crystalline nuclei to semiconductor and metallic nanocrystals. Experimental results show that Te, CdTe, Ag2Te, CuTe, NiTe1.5, CoTe1.5, Bi2Te3, Sb2Te3, Bi-Sb, In2Te3, Ni2.9SnTe2, CuGaTe2, and CuInS2 semiconductors and Bi, Sb, Ag, Cu, and Ni metallic nanocrystals can be prepared by this method. Transmission electron microscopy observations show that the obtained Bi, Ag2Te, Bi2Te3, Sb2Te3, CdTe, and NiTe1.5 nanocrystals have grain sizes in the nanometer range. The types of metallic and semiconductor phase that can be obtained by this method are explained by the thermodynamical criterion based on calculations of the Gibbs free energy and electrode potential. It is proposed that the crystalline phase of the final product is controlled by the change of the Gibbs free energies of the reactions of the metal oxide with reducing gases and the metal oxide redox electrode potentials, not the metal redox standard electrode potentials and electronegativities of the elements. Furthermore, a prediction is presented for the preparation of other kinds of binary and ternary compound based on the thermodynamical criterion. Our results provide new insight into facile and green preparation of semiconductor and metal nanocrystals.

Polymerized-complex method for preparation of supported bimetallic alloy and monometallic nanoparticles.

Herein, we report a novel polymerized-complex method for the preparation of Ni-Pd, Ni-Pt, and Cu-Pt alloys and Pt, Pd, Ag, Ni, and Cu nanoparticles. The grain sizes and crystalline phases of these nanoparticles can be controlled. These nanoparticles are obtained via the formation of a polymerized complex and release of reducing gases during N2-protected calcination.

Molecular dynamics study of the structures and properties of RDX/GAP propellant.

Molecular dynamics simulations have been performed to investigate well-known energetic material cyclotrimethylene trinitramine (RDX) crystal, glycidyl azide polymer (GAP) and RDX/GAP propellant. The results show that the binding energies on different crystalline surface of RDX change in the order of (0 1 0) > (1 0 0) > (0 0 1). The interactions between RDX and GAP have been analyzed by means of pair correlation functions. The mechanical properties of RDX/GAP propellant, i.e., elastic coefficients, modulus, Cauchy pressure, and Poisson's ratio, etc., have been obtained. It is found that mechanical properties are effectively improved by adding some amounts of GAP polymer, and the overall effect of GAP on three crystalline surfaces of RDX changes in the order of (1 0 0) > (0 1 0) > (0 0 1). The energetic properties of RDX/GAP propellant have also been calculated and the results show that compared with the pure RDX crystal, the standard theoretical specific impulse (I(sp)) of RDX/GAP propellant decrease, but they are still superior to those of double base propellant.

[Thinking about acupuncture for treatment of simple obesity].

In the viewpoint of traditional Chinese medicine (TCM), the authors consider that simple obesity is not a disease, which does not fit to be treated according to the models of diagnosis and treatment in TCM. Considering its cause, pathogenesis, syndrome differentiation, principles and methods of treatment, as well as experimental study, etc. , the authors point out that the true effects of acupuncture on weight-loss should be investigated alone and avoid the influence of diet and exercise. Until now, what we have done on the acupuncture for treatment of simple obesity is not sufficient to verify the direct effects of acupuncture for weight-loss. The correct way for weight-loss is health care including dietary regime and regular life schedule. Comparatively, the treatment as the main choice for weight-loss is not recommended.

Dependence of particle morphology and size on the mechanical sensitivity and thermal stability of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine.

Three kinds of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) samples with spherical (beta-phase), needle (gamma-phase) and polyhedral (beta-phase) shapes were fabricated by wet milling, solvent/non-solvent and riddling methods, respectively. By changing the technical conditions, HMX powders with different particle sizes were obtained for each kind of sample. All as-prepared samples were characterized by laser granularity measurement, scanning electron microscopy (SEM) and X-ray diffractometry (XRD). Taking advantage of mechanical sensitivity tests, slow cook-off tests and differential scanning calorimetry (DSC) analysis, the mechanical sensitivity and thermal stability of HMX samples were found to depend on particle size and morphology. Results indicated that particle size played a significant role in the safety of HMX, and that morphology regulated the experimental results, i.e., for each kind of HMX samples, the mechanical sensitivity and thermal stability of HMX changed if the particle size differed. However, the trends of these changes exhibit much variance if the microstructure of the HMX particles is altered. Consequently, the difference in safety for these kinds of samples has to do with their specific morphology.