Development of a Novel Energy Saving and Environmentally Friendly Starch via a Graft Copolymerization Strategy for Efficient Warp Sizing and Easy Removal.

Warp sizing is a key process in textile production. However, before the yarn/fabric finishing, such as dyeing, the paste adhering to the warp must be eliminated to ensure optimal dyeing properties and the flexibility of the fabric. Therefore, the sizing will often consume a lot of energy and produce a lot of industrial wastewater, which will cause serious harm to the environment. In this study, we have developed an energy saving and environmentally friendly starch-based slurry by modifying natural starch with acrylamide. The paste has excellent viscosity stability and fiber adhesion, and exhibits excellent performance during warp sizing. In addition, the slurry has good water solubility at 60-70 °C, so it is easy to desize at low temperatures. Because of this, the sizing of the warp can be deslimed directly from the yarn during subsequent washing processes. This work can not only reduce some costs for the textile industry, but also achieve the purpose of energy conservation and emission reduction.

Self-similar chiral organic molecular cages.

The endeavor to enhance utility of organic molecular cages involves the evolution of them into higher-level chiral superstructures with self-similar, presenting a meaningful yet challenging. In this work, 2D tri-bladed propeller-shaped triphenylbenzene serves as building blocks to synthesize a racemic 3D tri-bladed propeller-shaped helical molecular cage. This cage, in turn, acts as a building block for a pair of higher-level 3D tri-bladed chiral helical molecular cages, featuring multilayer sandwich structures and displaying elegant characteristics with self-similarity in discrete superstructures at different levels. The evolutionary procession of higher-level cages reveals intramolecular self-shielding effects and exclusive chiral narcissistic self-sorting behaviors. Enantiomers higher-level cages can be interconverted by introducing an excess of corresponding chiral cyclohexanediamine. In the solid state, higher-level cages self-assemble into supramolecular architectures of L-helical or D-helical nanofibers, achieving the scale transformation of chiral characteristics from chiral atoms to microscopic and then to mesoscopic levels.

Practical and environment-friendly indirect electrochemical reduction of indigo and dyeing.

Indigo has been widely used as a dye in the industrial dyeing due to its good color fastness in dyeing cellulose fibers. However, excess reducing agent, "insurance powder (Na2S2O4)", was always used in the actual production of the factory, sparking serious pollution (water pollution and air pollution). Herein, we developed a practical and environment-friendly indirect electrochemical reduction of indigo, and applied this method for cloth dyeing. The electrochemical device was designed in the combination of source of electro-catalytic reduction and dyeing. The iron-triethanolamine-calcium gluconate (Fe-TEOA-Ca) complex played a role of key intermediate, and ultrasonic wave was found to speed up the indirect electro-catalytic process. The electrochemical performance of intermedia was improved by calcium ion addition. Washed with oxalic acid solution, the dyed fabric could achieve the level of color fastness in industry standard. Generally speaking, our method leads to a green route for indigo reduction using electrochemistry, which may change the crafting process of indigo dyeing in industry.

The dissociation of nitramide and methylnitramine when confined inside armchair single-walled carbon nanotubes.

Chemical reactivity and molecular structure of energetic materials may be significantly changed when they are confined inside carbon nanotubes (CNTs). The ONIOM calculations were carried out to investigate the molecular structures and the N-N bond decomposition of nitramide (NA) and methylnitramine (MNA) confined inside armchair single-walled CNTs with different diameter. Results showed that confinement in CNT(6, 6) and CNT(7, 7) had no evident influence on the structure of NA and MNA. However, the structures of NA and MNA within CNT(5, 5) were altered significantly with respect to the structures of the isolated NA and MNA. Compared with NA, MNA showed stronger interaction with these CNTs studied. By analyzing the potential energy curve along the N-N bond, we found that the energy barriers of the N-N bond decomposition for the NA and MNA are decreased by 11.6 and 10.8 kcal/mol, respectively, due to the confinement of CNT(5, 5). Confinement in CNT(6, 6) resulted in a slight decrease in the activation energy. Confinement in CNT(7, 7) did not affect the thermal decomposition of NA and MNA. We conclude that the N-N bond dissociation of NA and MNA can be promoted by confinement in a CNT with small diameter.

Initial reactions of methyl-nitramine confined inside armchair (5,5) single-walled carbon nanotube.

The dissociation and isomerization reactions of methyl-nitramine(MNA) confined inside armchair CNT(5,5) single-walled carbon nanotube were investigated by using the ONIOM (B3LYP/6-311++G:UFF) method. The results showed that some geometries of the confined MNA were modified by the CNT(5,5) in comparison with the structure of the isolated MNA. By analyzing the relevant structures and energies involved in the dissociation and isomerization reactions, we found that the transition state structures of the isomerization reactions to form CH(3)NHONO (R1) and CH(3)NNOOH (R2) were modified by the confinement of CNT(5,5). However, this confinement does not evidently affect the transition state structure of the HONO elimination reaction (R3). In addition, no transition state was found for the N-N bond dissociation (R4) of the isolated MNA, but this dissociation process occurred via a transition state for the confined MNA. When MNA was confined inside CNT(5,5), the activation energies of R1, R2, and R4 were decreased obviously but the energy barrier of R3 was increased slightly. The order of activation energy for these four initial reactions was also changed by the confinement of CNT(5,5). Furthermore, it was found that the relative energies of the intermediates formed by the isomerization and dissociation of MNA were also modified by the confinement of CNT(5,5). These intermediates become more stable in the confined case than in the isolated case. It was concluded that the initial reactions of MNA could be modified evdiently by confinement within a carbon nanotube.

Theoretical study on the trans-cis isomerization and initial decomposition of energetic azofurazan and azoxyfurazan.

In this work, we carried out the hybrid density functional theory (DFT) calculations in order to understand the thermal trans-cis isomerization and initial thermal decomposition of 3,3'-diamino-4,4'-azofurazan (DAAzF), 3,3'-diamino-4,4'-azoxyfurazan (DAAF), 3,3'-dinitro-4,4'-azofurazan (DAAF) and 3,3'-dinitro-4,4'-azoxyfurazan (DAAzF). The relative energy between the trans- and cis-isomer was also calculated at the B3LYP/6-311++G(d,p)//B3LYP/6-31G(d) level of theory. We found that a negative correlation existed between the relative energy and the sensitivity for these energetic azofurazan and azoxyfurazan compounds, where the higher relative energy means the lower the sensitivity. It was also found that the oxidation of azo-group could cause the decreasing in the relative energy between the trans- and cis-isomer, as well as the alteration of the isomerization mechanism. An inversion mechanism operates for azofurazan compounds (DAAzF and DNAF) while a rotation mechanism works for azoxyfurazan compounds (DAAF and DNOAF). Compared with the thermal trans-cis isomerization, the homolytic cleavage of C-N bond needs to overcome a much higher energy barrier, which indicates that the energy of the external stimulus should firstly trigger the trans-cis isomerization, rather than the breakage of C-N bond. A self-desensitization effect caused by the reversible thermal trans-cis isomerization process was firstly proposed to explain that the azofurazan and azoxyfurazan compounds are class of energetic materials with lower sensitivity. This new concept (self-desensitization effect) is expected to be useful to design the novel high density, insensitive energetic material.

Isomerization and electronic relaxation of azobenzene after being excited to higher electronic states.

In this work, some critical structures (e.g. stable structure, transition state, local minimum and conical intersection) of azobenzene photoisomerization were optimized by means of ab initio CASSCF calculation. The potential energy surfaces for the CNNC dihedral torsion and CNN bond angle concerted-inversion pathway were mapped to explore the relaxation process of azobenzene (AB) photoisomerization. The results indicate that the rotational mechanism favors the photoisomerization of the S(1)(n,pi*) and S(2)(pi,pi*) trans-AB. The concerted-inversion mechanism may operate in the decay process of S(2)(pi,pi*) or higher state trans-AB. By borrowing the (n,pi*; pi,pi*) and (n(2),pi*(2)) electronic states, trans-AB upon excitation to the higher states can quickly relax to the S(1)(n,pi*) or ground state via the rotation or concerted-inversion pathway. The forming ground-state species with higher vibrational energy from the higher excited states will become the stable trans-isomer through the concerted-inversion pathway. These relaxation processes have been confirmed by the conical intersections calculated by the high-level CASSCF method.

Ab initio calculations of the effects of H+ and NH4+ on the initial decomposition of HMX.

In this work, the effects of H(+) and NH(4)(+) on the initial decomposition of HMX were investigated on the basis of the B3P86/6-31G** and B3LYP/6-31G* calculations. Three initial decomposition pathways including the N-NO(2) bond fission, HONO elimination and C-N bond dissociation were considered for the complexes formed by HMX with H(+) (PHMX1 and PHMX2) or with NH(4)(+) (AHMX). We found that H(+) and NH(4)(+) did not evidently induce the HMX to trigger the N-NO(2) heterolysis because the energy barrier of N-NO(2) heterolysis was found to be higher than the bond dissociation energy of N-NO(2) homolytic cleavage. Meanwhile, the transition state barriers of the HONO elimination from the complexes were found to be similar to that from the isolated HMX, which means that the HONO elimination reaction of HMX was not affected by the H(+) and NH(4)(+). As for the ring-opening reaction of HMX due to the C-N bond dissociation, the calculated potential energy profile showed that the energy of the complex (AHMX) went uphill along the C-N bond length and no transition state existed on the curve. However, the transition state energy barriers of C-N bond dissociation were calculated to be only 5.0 kcal/mol and 5.5 kcal/mol for the PHMX1 and PHMX2 complexes, respectively, which were much lower than the C-N bond dissociation energy of isolated HMX. Moreover, among the three initial decomposition reactions, the C-N bond dissociation was also the most energetically favorable pathway for the PHMX1 and PHMX2. Our calculation results showed that the H(+) can significantly promote the initial thermal decomposition of C-N bond of HMX, which, however, is influenced by NH(4)(+) slightly.