The development of a pseudo-one pot synthesis of 3（5）,4-dinitropyrazole enabled us to use it as a starting material for energetic plasticisers. Its acidic proton allowed simple derivatisation on one of the ring nitr...The development of a pseudo-one pot synthesis of 3（5）,4-dinitropyrazole enabled us to use it as a starting material for energetic plasticisers. Its acidic proton allowed simple derivatisation on one of the ring nitrogens. The thermal characteristics of two derivatives were evaluated. For instance, the N-allyl compound was a liquid with very low glass transition temperature, whereas the N-propargyl compound was a sticky solid at ambient temperature. The two compounds were both thermally stable according to STANAG 4582.展开更多
In the field of highly integrated printed circuit board （PCB）, the heat resistant substrate with low water absorption is very important material. To get the resin composition for the high functional substrate materi...In the field of highly integrated printed circuit board （PCB）, the heat resistant substrate with low water absorption is very important material. To get the resin composition for the high functional substrate material with low moisture absorption and high glass transition temperature （Tg） simultaneously, a fluorenyl ＂Cardo＂ epoxy was incorporated into novolac cyanate ester resin. As an optimum curing agent for the fiuorenyl epoxy, methyl nadic anhydride （MNA） was selected. Silica powders as fillers were added into the resin composition. The partial replacement of the cyanate ester resin with the fluorenyl epoxy could reduce the moisture absorption with keeping high glass transition temperature over 300 ℃. The laminate, which was fabricated from prepregs made with 40 wt% silica-filled resin composition and glass fabric, showed high Tg of 317 ℃ and low moisture absorption of 0.57%.展开更多
Poly(dibutyl itaconate-co-isoprene-co-methacrylic acid)(PDIM) elastomer was designed and synthesized by redox emulsion polymerization under mild conditions. PDIM has high molecular weight, relatively high yield, and l...Poly(dibutyl itaconate-co-isoprene-co-methacrylic acid)(PDIM) elastomer was designed and synthesized by redox emulsion polymerization under mild conditions. PDIM has high molecular weight, relatively high yield, and low glass transition temperature(Tg). The structure of PDIM was determined by FTIR and NMR, and the carboxyl content was obtained by titration in a non-proton solvent. Tensile strength and elongation at break increased with increasing carboxyl content. In addition, the interaction between PDIM and silica was elucidated by rubber process analyzer(RPA) and TEM, and the results showed that the silica-PDIM interaction was strong, but the silica-silica interaction was weak.展开更多
In terms of the classical theory in textbooks, the two components with phase separation in a binary polymer blend will, depending on their compatibility, have their respective Tg get closer or remain in their original...In terms of the classical theory in textbooks, the two components with phase separation in a binary polymer blend will, depending on their compatibility, have their respective Tg get closer or remain in their original values. According to the classical theory, the Tg of plastic component shall remain unchanged or move toward the lower Tg of rubber component in a rubber/plastic blend. However, ultra-fine full-vulcanized powdered rubber (UFPR) with a diameter of ca. 100 nm can simultaneously increase the toughness and the Tg of plastics, which is abnormal and is difficult to explain by classical theory. In this feature article, the abnormal behavior and its mechanism are discussed in detail.展开更多
A novel hyperbranched poly(urethane-tetrazole)(HPUTZ) was synthesized via the "A2+BB2' " approach using hexadiisocyanate(HDI) and 3-(bis-(2-hydroxyethyl)) aminopropyltetrazole(HAPTZ).The molecular struct...A novel hyperbranched poly(urethane-tetrazole)(HPUTZ) was synthesized via the "A2+BB2' " approach using hexadiisocyanate(HDI) and 3-(bis-(2-hydroxyethyl)) aminopropyltetrazole(HAPTZ).The molecular structure was characterized by FTIR and 1H NMR spectroscopy.The number average molecular weight was measured to be 1.05×104 g/mol with a polydispersity of 1.27 by GPC analysis.The HPUTZ was further cured by the semi-adduct(PEG-IPDI) from polyethylene glycol(PEG) reacting with isophorone diisocyanate(IPDI) to form the crosslinked HAPTZ-PU film in different ratio of HAPTZ to PEG-IPDI.The glass transition temperature of HAPTZ-PU increased from 44.9 to 56.4 ℃ as the HPUTZ content increased from 20% to 33% from the DSC analysis.The DMA results indicated that the HPUTZ-PU with 20% HPUTZ possessed the highest storage modulus and loss tangent.However,the storage modulus increased with the increasing of HPUTZ segment at higher temperature.The shape memory study showed that all the films presented the excellent shape memory function.Over 98% shape recovery could be obtained for the HAPTZ-PU with 20%-33% HAPTZ segment content within 60 s in the tension deformation test and within 40 s at 80 ℃ in the bend deformation test.展开更多
Up to now the chirality is seldom studied in the diluted spin glass although many investigations have been performed on the site-ordered Edwards-Anderson model. By simulation, we investigate the dynamicaJ properties o...Up to now the chirality is seldom studied in the diluted spin glass although many investigations have been performed on the site-ordered Edwards-Anderson model. By simulation, we investigate the dynamicaJ properties of both the spin-glass and the chiral-glass phases in a diluted dipolar system, which was manifested to have a spin-glass transition by recent numerical study. By scaling we find that both phases have the same aging behavior and closer aging parameterμ. Similarly, the domains grow in the same way and both phases have a closer barrier exponent g2. It means that both the spins and the chirality have the same dynamical properties and they may freeze at the same temperature.展开更多
Thin films of block copolymers （BCPs） are widely accepted as potentially important materials in a host of technological applications including nano- lithography. In order to induce domain separation and form well-de...Thin films of block copolymers （BCPs） are widely accepted as potentially important materials in a host of technological applications including nano- lithography. In order to induce domain separation and form well-defined structural arrangements, many of these are solvent-annealed （i.e. solvent swollen） at moderate temperatures. The use of solvents can be challenging in industry from an environmental point of view as well as having practical/cost issues. However, a simple and environmentally friendly alternative to solvo-thermal annealing for the periodically ordered nanoscale phase separated structures is described herein. Various asymmetric polystyrene-b-poly（ethylene oxide） （PS-b-PEO） thin films were annealed in a compressible fluid, supercritical carbon dioxide （scCO2）, to control nanodomain orientation and surface morphologies. For the first time, periodic well defined, hexagonally ordered films with sub-25 nm pitch size were demonstrated using a supercritical fluid （SCF） process at low temperatures and pressures. Predominant swelling of PEO domains in scCO2 induces nanophase separation, scCO2 serves as green alternative to the conventional organic solvents for the phase segregation of BCPs with complete elimination of any residual solvent in the patterned film. The depressurization rate of scCO2 following annealing was found to affect the morphology of the films. The supercritical annealing conditions could be used to define nanoporous analogues of the microphase separated films without additional processing, providing a one-step route to membrane like structures without affecting the ordered surface phase segregated structure. An understanding of the BCP self- assembly mechanism can be realized in terms of the deviation in glass transition temperature, melting point, viscosity, interaction parameter and volume fraction of the constituent blocks in the scCO2 environment.展开更多
文摘The development of a pseudo-one pot synthesis of 3（5）,4-dinitropyrazole enabled us to use it as a starting material for energetic plasticisers. Its acidic proton allowed simple derivatisation on one of the ring nitrogens. The thermal characteristics of two derivatives were evaluated. For instance, the N-allyl compound was a liquid with very low glass transition temperature, whereas the N-propargyl compound was a sticky solid at ambient temperature. The two compounds were both thermally stable according to STANAG 4582.
文摘In the field of highly integrated printed circuit board （PCB）, the heat resistant substrate with low water absorption is very important material. To get the resin composition for the high functional substrate material with low moisture absorption and high glass transition temperature （Tg） simultaneously, a fluorenyl ＂Cardo＂ epoxy was incorporated into novolac cyanate ester resin. As an optimum curing agent for the fiuorenyl epoxy, methyl nadic anhydride （MNA） was selected. Silica powders as fillers were added into the resin composition. The partial replacement of the cyanate ester resin with the fluorenyl epoxy could reduce the moisture absorption with keeping high glass transition temperature over 300 ℃. The laminate, which was fabricated from prepregs made with 40 wt% silica-filled resin composition and glass fabric, showed high Tg of 317 ℃ and low moisture absorption of 0.57%.
基金supported by the National Natural Science Foundation of China(50933001,51221102)the National Science Fund for Distinguished Young Scholars(50725310)+3 种基金the National Basic Research Program of China(2011 CB606003)the Beijing Nova Program(Z131102000413015)the Beijing Municipal Training Program Foundation for the Talents(2013D003034 00041)the Goodyear Tire & Rubber Company
文摘Poly(dibutyl itaconate-co-isoprene-co-methacrylic acid)(PDIM) elastomer was designed and synthesized by redox emulsion polymerization under mild conditions. PDIM has high molecular weight, relatively high yield, and low glass transition temperature(Tg). The structure of PDIM was determined by FTIR and NMR, and the carboxyl content was obtained by titration in a non-proton solvent. Tensile strength and elongation at break increased with increasing carboxyl content. In addition, the interaction between PDIM and silica was elucidated by rubber process analyzer(RPA) and TEM, and the results showed that the silica-PDIM interaction was strong, but the silica-silica interaction was weak.
文摘In terms of the classical theory in textbooks, the two components with phase separation in a binary polymer blend will, depending on their compatibility, have their respective Tg get closer or remain in their original values. According to the classical theory, the Tg of plastic component shall remain unchanged or move toward the lower Tg of rubber component in a rubber/plastic blend. However, ultra-fine full-vulcanized powdered rubber (UFPR) with a diameter of ca. 100 nm can simultaneously increase the toughness and the Tg of plastics, which is abnormal and is difficult to explain by classical theory. In this feature article, the abnormal behavior and its mechanism are discussed in detail.
基金support of the National Natural Science Foundation of China (50633010) is gratefully acknowledged
文摘A novel hyperbranched poly(urethane-tetrazole)(HPUTZ) was synthesized via the "A2+BB2' " approach using hexadiisocyanate(HDI) and 3-(bis-(2-hydroxyethyl)) aminopropyltetrazole(HAPTZ).The molecular structure was characterized by FTIR and 1H NMR spectroscopy.The number average molecular weight was measured to be 1.05×104 g/mol with a polydispersity of 1.27 by GPC analysis.The HPUTZ was further cured by the semi-adduct(PEG-IPDI) from polyethylene glycol(PEG) reacting with isophorone diisocyanate(IPDI) to form the crosslinked HAPTZ-PU film in different ratio of HAPTZ to PEG-IPDI.The glass transition temperature of HAPTZ-PU increased from 44.9 to 56.4 ℃ as the HPUTZ content increased from 20% to 33% from the DSC analysis.The DMA results indicated that the HPUTZ-PU with 20% HPUTZ possessed the highest storage modulus and loss tangent.However,the storage modulus increased with the increasing of HPUTZ segment at higher temperature.The shape memory study showed that all the films presented the excellent shape memory function.Over 98% shape recovery could be obtained for the HAPTZ-PU with 20%-33% HAPTZ segment content within 60 s in the tension deformation test and within 40 s at 80 ℃ in the bend deformation test.
基金Supported by National Natural Science Foundation of China under Grant Nos.11247428,61274101Natural Science Foundation of Liaoning Province under Grant No.20121078
文摘Up to now the chirality is seldom studied in the diluted spin glass although many investigations have been performed on the site-ordered Edwards-Anderson model. By simulation, we investigate the dynamicaJ properties of both the spin-glass and the chiral-glass phases in a diluted dipolar system, which was manifested to have a spin-glass transition by recent numerical study. By scaling we find that both phases have the same aging behavior and closer aging parameterμ. Similarly, the domains grow in the same way and both phases have a closer barrier exponent g2. It means that both the spins and the chirality have the same dynamical properties and they may freeze at the same temperature.
文摘Thin films of block copolymers （BCPs） are widely accepted as potentially important materials in a host of technological applications including nano- lithography. In order to induce domain separation and form well-defined structural arrangements, many of these are solvent-annealed （i.e. solvent swollen） at moderate temperatures. The use of solvents can be challenging in industry from an environmental point of view as well as having practical/cost issues. However, a simple and environmentally friendly alternative to solvo-thermal annealing for the periodically ordered nanoscale phase separated structures is described herein. Various asymmetric polystyrene-b-poly（ethylene oxide） （PS-b-PEO） thin films were annealed in a compressible fluid, supercritical carbon dioxide （scCO2）, to control nanodomain orientation and surface morphologies. For the first time, periodic well defined, hexagonally ordered films with sub-25 nm pitch size were demonstrated using a supercritical fluid （SCF） process at low temperatures and pressures. Predominant swelling of PEO domains in scCO2 induces nanophase separation, scCO2 serves as green alternative to the conventional organic solvents for the phase segregation of BCPs with complete elimination of any residual solvent in the patterned film. The depressurization rate of scCO2 following annealing was found to affect the morphology of the films. The supercritical annealing conditions could be used to define nanoporous analogues of the microphase separated films without additional processing, providing a one-step route to membrane like structures without affecting the ordered surface phase segregated structure. An understanding of the BCP self- assembly mechanism can be realized in terms of the deviation in glass transition temperature, melting point, viscosity, interaction parameter and volume fraction of the constituent blocks in the scCO2 environment.
