Conventional firefighting clothing and fire masks can protect firemen’s safety to a certain extent,whereas cannot perceive environmental hazards and monitor their physical status in real time.Herein,we fabricated two...Conventional firefighting clothing and fire masks can protect firemen’s safety to a certain extent,whereas cannot perceive environmental hazards and monitor their physical status in real time.Herein,we fabricated two kinds of Janus graphene/poly(pphenylene benzobisoxazole)(PBO)fabrics by laser direct writing approach and evaluated their performance as intelligent firefighting clothes and fire masks.The results showed that the Janus graphene/PBO fabrics were virtually non-combustible and achieved the highest thermal protection time of 18.91 s ever reported in flame,which is due to the intrinsic flame-retardant nature of PBO fibers.The graphene/PBO woven fabrics-based sensor showed good repeatability and stability in human motion monitoring and NO_(2)gas detection.Furthermore,the piezoelectric fire mask was assembled with graphene/PBO nonwoven fabric as electrode layer and polyvinylidene fluoride(PVDF)electrostatic direct writing film as piezoelectric layer.The filtration efficiency of the fire mask reaches 95%for PM_(2.5)and 100%for PM_(3.0),indicating its effective filtration capability for smoke particles in fires.The respiratory resistance of the piezoelectric fire mask(46.8 Pa)was lower than that of commercial masks(49 Pa),showing that it has good wearing comfort.Besides,the piezoelectric fire mask can be sensitive to the speed and intensity of human breathing,which is essential for indirectly reflecting the health of the human body.Consequently,this work provides a facile approach to fabricate next-generation intrinsic flame-retardant smart textiles for smart firefighting.展开更多
A series of soluble poly(p-phenylene vinylene) (PPV) derivatives were synthesized through dehydrochlorination with the p-metaoxy phenol as starting materials. The electronic characteristics of PPV derivatives were stu...A series of soluble poly(p-phenylene vinylene) (PPV) derivatives were synthesized through dehydrochlorination with the p-metaoxy phenol as starting materials. The electronic characteristics of PPV derivatives were studied.展开更多
A non-aqueous suspension polycondensation method was proposed to proceed the reaction ofp-phenylenediamine and terephthaloyl chloride for the preparation of poly（p-phenylene terephthalamide） （PPTA）. The system was...A non-aqueous suspension polycondensation method was proposed to proceed the reaction ofp-phenylenediamine and terephthaloyl chloride for the preparation of poly（p-phenylene terephthalamide） （PPTA）. The system was operated with NMP-CaCI2 solution as the dispersed phase and inert liquid paraffin as the continuous phase. Each of NMP-CaCl2 solution microdroplet suspended in paraffin served as a microreactor where the polycondensation took place. According to the results of TGA, XRD, IR, SEM and EA, PPTA with good quality was obtained through this novel method, and a number of main factors influencing this process were investigated to determine the optimum condition for the preparation of PPTA. Besides, this two-phase polycondensation system brings many unique advantages compared to the conventional solution polycondensation method, including a sealed reaction environment keeping the reactants away from oxygen and water, easy removal of HCI to promote the reaction, well-controlled temperature and low viscosity which means less energy cost.展开更多
Poly（phenylene sulfide） （PPS） with different crosslinking levels was successfully fabricated by means of high- temperature isothermal treatment （IT）. The crosslinking degree of PPS was increased with IT time as ...Poly（phenylene sulfide） （PPS） with different crosslinking levels was successfully fabricated by means of high- temperature isothermal treatment （IT）. The crosslinking degree of PPS was increased with IT time as revealed by Fourier-transform infrared spectroscopy and dynamic viscosity measurements. Its influence on the non-isothermal crystallization behaviors of PPS was studied by differential scanning calorimeter （DSC）. The crystallization peak temperature of PPS with 6 h IT was 15 K higher than that of the one with 2 h IT at 30 K/min cooling rate. The non-isothermal crystallization data were also analyzed based on the Ozawa model. The Ozawa exponent m decreased from 3.5 to 2.2 at 232~C with the increase of the IT time, suggestive of intensive thermal oxidative crosslinking reducing the crystallite dimension as PPS crystal grew. The reduced cooling crystallization function K（T） was indicative of the larger activation energy of crosslinked PPS chain diffusion into crystal lattice, resulting in a slow crystal growth rate. Additionally, the overall crystallization rate of PPS was also accelerated with the increase of crosslinking degree from the observation of polarized optical micrograph. These results indicated that the chemical crosslinked points and network structures formed during the high-temperature isothermal treatment acted as the effective nucleating sites, which greatly promoted the crystallization process of PPS and changed the type of nucleation and the geometry of crystal growth accordingly.展开更多
Today the developed yarn muscles or actuators still cannot satisfy the requirements of working in high-temperature environ-ments.Thermal resistivity is highly needed in aerospace and industrial protection applications...Today the developed yarn muscles or actuators still cannot satisfy the requirements of working in high-temperature environ-ments.Thermal resistivity is highly needed in aerospace and industrial protection applications.Herein,an artificial muscle with high-temperature tolerance is prepared using carbon nanotube(CNT)wrapped poly(p-phenylene benzobisoxazole)(PBO)composite yarns.A thermal twisting method was utilized to reorientate the stiff PBO molecular chains into a uniform and twist-stable coiled structure.The CNT/PBO composite yarn muscle generates reversible contractile strokes up to 18.9%under 5.4 MPa tension and outputs 1.3 kJ kg^(-1) energy density.In contrast to previous actuators,which are normally oper-ated at room temperatures,the CNT/PBO composite yarn muscles can work at ambient temperatures up to 300℃ with high contractile stroke and long-term stability.A bionic inchworm robot,a deployable structure,and smart textiles driven by the high-temperature-tolerant yarn muscles were demonstrated,showing the promise as a soft actuator towards high-temperature environment applications.展开更多
Materials with emission over the whole visible range(400-800 nm)have been obtained through incorporating single-colored CdTe nanocrystals(NCs)into a poly(p-phenylene vinylene)(PPV)precursor[the sulfonium polyelectroly...Materials with emission over the whole visible range(400-800 nm)have been obtained through incorporating single-colored CdTe nanocrystals(NCs)into a poly(p-phenylene vinylene)(PPV)precursor[the sulfonium polyelectrolyte precursor of PPV].Firstly,the quantum yield(QY)of the PPV precursor was improved to~50%via heat treatment of a mixed solution of the PPV precursor and poly(vinyl alcohol)(PVA)at 100°C for 3 min.Then,single-colored CdTe NCs were incorporated into the mixed solution.The introduction of the PVA was necessary to reduce the electrostatic interaction between the PPV precursor and CdTe NCs,which improved their compatibility.The reduced electrostatic interaction eliminated Förster resonance energy transfer(FRET)processes between NCs,as well as between NCs and the PPV precursor,which allowed the functional integration of the polymer and NCs.Consequently,polymer/NC composites with almost any Commission Internationale de L’Eclairage(CIE)coordinates can be achieved by simply changing the size and amount of the NCs.In particular,when the emission wavelength of the CdTe NCs was 559 nm,a pure white-light emitting material with CIE coordinates(0.337,0.332)was obtained.展开更多
The morphology and crytal structure of poly(p-phenylene terephthalate) (PPT), prepared by confined thin filmmelt (CTFMP) and solution (CTFSP) and bulk solution polymerization, were characterized by transmission electr...The morphology and crytal structure of poly(p-phenylene terephthalate) (PPT), prepared by confined thin filmmelt (CTFMP) and solution (CTFSP) and bulk solution polymerization, were characterized by transmission electronmicroscopy, electron dimaction and molecular modeling. The unit cell is monoclinic (P2_1/a space group) with parameters a =7.89, b = 5.49, c = 12.65 A, α=γ= 90°, β=100.33°, density = 1.48 g/cm^3, the a, b and β values differing slightly from thosereported previously in the literature. A degree of variation in relative intensities of hk0 reflections in, apparently, untilted[001] ED patterns was observed from a given sample, suggesting some variation in molecular packing. ED evidence wasfound for a second phase, with [001] appearing the same as for phase Ⅱ of the related poly(p-oxybenzoate) (PpOBA)polymer. CTFMP crystals polymerized above 220℃ (up to 370℃) and CTFSP crystals polymerized at 300℃ consisted oflamellae 100-200 A thick.展开更多
Dispersion of multi-walled carbon nanotubes in poly（p-phenylene） composite exposed to toluene was experimentally investigated. 3 mg of multi-walled carbon nanotubes with nominal size of 20 nm was compounded with 30 ...Dispersion of multi-walled carbon nanotubes in poly（p-phenylene） composite exposed to toluene was experimentally investigated. 3 mg of multi-walled carbon nanotubes with nominal size of 20 nm was compounded with 30 mg of poly（p-phenylene） with the presence of terpineol as binding initiator. To investigate an optimal condition for homogenizing all constituents, ultrasonication with an output power of 750W was employed with compounding time of 3, 10, 20 and 30 min. With FTIR analyses, it could be confirmed that homogeneous composite of multi-walled carbon nanotubes and poly（p-phenylene） could be prepared. SEM analyses were also conducted to examine the dispersion of multi-walled carbon nanotubes in the polymer matrix. Then intrinsic electrical resistance of the composites after being exposed to toluene was also investigated. It was found that the composite film prepared with ultrasonication for 20 min could provide sufficiently sensitive response with respect to varied concentration of toluene.展开更多
Commercial poly(p-phenylene sulfide) (PPS) was thermally cured, which resulted in an increase of molecular weight due to cross-linking. Non-isothermal crystallization studies of samples cured for up to 7 days at 250?C...Commercial poly(p-phenylene sulfide) (PPS) was thermally cured, which resulted in an increase of molecular weight due to cross-linking. Non-isothermal crystallization studies of samples cured for up to 7 days at 250?C showed a monotonous increase of crystallization temperature compared to pure PPS. However, a further increase of curing time decreased the crystallization temperature. The change in the half-crystallization time (t1/2) was similar to the crystallization temperature. Thus, the cross-linking of PPS affected crystallization behaviors significantly. To a certain extent, crosslinks acted as nucleation agents, but excessive cross-linking hindered the crystallization. Morphologies observed by polarized optical microscopy suggested that thermal curing for as little as 1 day contributed to the spherulitic structure having a smaller size, that was not observed with pure PPS.展开更多
High viscous PPTA copolymer is prepared by low temperature solution copolycondensation of terephth-aloylchloride, p-phenylenediamine and p, p'-diamino-phenylpiperazine in the NMP-CaCl2 solvent system. The inherent...High viscous PPTA copolymer is prepared by low temperature solution copolycondensation of terephth-aloylchloride, p-phenylenediamine and p, p'-diamino-phenylpiperazine in the NMP-CaCl2 solvent system. The inherent viscosity of all copolymers is more than 5. If more quantity of 3rd monomer is introduced into the macromolecular chain, the inherent viscosity becomes higher. The copolymer's ash content is less than 1000 μg/g. The heat durability of copolymer is close to that of PPTA, and its dissolubility is superior to that of PPTA.展开更多
The morphology of PPTA pulp is investigated by means of optical microscope and scanningelectron microscope (SEM). It shows that PPTA pulp has feather-like branch, needle point-likeend, and irregular cross-section, whi...The morphology of PPTA pulp is investigated by means of optical microscope and scanningelectron microscope (SEM). It shows that PPTA pulp has feather-like branch, needle point-likeend, and irregular cross-section, which are very important for PPTA pulp as a reinforcer. Theseparation limitation of PPTA pulp is also investigated from both torn and brittle break cross-sec-tion. A packing mechanism is proposed to illustrate the microfibril packing in the gel system.展开更多
The conventional low-temperature method of solution polycondensation was developed to realize the reaction of p-phenylenediamin and terephthaloyl chloride for the preparation of poly（p-phenylene terephthalamide）（P...The conventional low-temperature method of solution polycondensation was developed to realize the reaction of p-phenylenediamin and terephthaloyl chloride for the preparation of poly（p-phenylene terephthalamide）（PPTA）. Some main factors influencing this process were investigated to determine the optimum condition for high molecular weight. Experiment showed significant slowing of the reaction and gradual deviation of second-order reaction kinetics due to diffusion control. These phenomena were studied theoretically via dynamic Monte Carlo simulation. A concise expression,n～c0^-0.88·t^0.37, was proposed to describe the diffusioncontrolled polycondensation process as a function of the monomer concentration and reaction time. The theoretical results provided a good description of diffusion-effected kinetics for the polycondensation process of PPTA, and demonstrated good agreement with the experimental data. Some differences of scaling relations between model and experiment results were also discussed.展开更多
The ab initio crystal orbital calculations on conjugated aromatic six-membered rings polymers, namely, poly(p-phenylene) (PPP), poly(2,5-pyridinediyl) (PPD), poly(2,5-phosphabenzene) (PPB) and ploy(2,5-arsabenzene) (P...The ab initio crystal orbital calculations on conjugated aromatic six-membered rings polymers, namely, poly(p-phenylene) (PPP), poly(2,5-pyridinediyl) (PPD), poly(2,5-phosphabenzene) (PPB) and ploy(2,5-arsabenzene) (PAB) are reported. The comparison of the important electronic properties of these polymers, such as band gap, bandwidth, ionization potential and electron affinity, indicates that PPP is the best intrinsic semiconductor, and PPD has the best prospects for forming n-doped conducting materials.展开更多
This paper deals with the relationships between the structure of poly（p-phenylene vinylene）（PPV） film and treatment temperature and their mechanical properties.The chemical structures and aggregated structures of ...This paper deals with the relationships between the structure of poly（p-phenylene vinylene）（PPV） film and treatment temperature and their mechanical properties.The chemical structures and aggregated structures of PPV precursor（PPVpre） and PPV treated at three node temperatures（125,155 and 230 ℃） were investigated by FTIR spectrometry and X-ray diffraction.The results show that the content of trans-conformation and the size of the crystalline domains increased with the increase of treatment temperature.The mechanical performances of the corresponding polymers were studied by nanoindentation.The elastic modulus and hardness of PPV films decreased with the increases of the content of trans-conformation and the size of the crystalline domains.These results suggest that the conformation and the size of the crystalline domains are able to induce the elastic modulus and hardness variation of PPV films.展开更多
The conformation, the chain packing stabilization and the unit cell modeling of poly(p-phenylene benzobisthiazole) have been investigated by using molecular simulation techniquein the present work. A coupling behaviou...The conformation, the chain packing stabilization and the unit cell modeling of poly(p-phenylene benzobisthiazole) have been investigated by using molecular simulation techniquein the present work. A coupling behaviour of σ-bond rotations at either side of the pheny-lene ring or the heterocyclic ring was found surely to exceed a length of the repeat unit ofthe polymer chain. For a single chain model, the stable torsion angle of the repeat resultedat 14°. In the crystalline cell minimization, the dihedral angle along the polymer chaincould even be stabilized in various values. It therefore indicates that the intermolecularinteraction does play a considerable role for this polymer forming the conformation. Ac-cording to cohesive energies calculated for these unit cell models, the torsion angle in themost stable crystalline cell is 0°. When the chains packing together, there exist so manyenergy stable wells along the chain axis 0.35--0.36nm apart from neighbouring chains.Most of the unit cells have quite closed cohesive energies. These factors thus cause thedifficulty of forming an unique perfect crystalline structure of the polymer. The presentstudy suggested a number of reasonable unit cells, and the most stable crystalline structurefor this polymer that is monoclinic, non-primitive unit cell.展开更多
The relationship between property and structure of poly( p-phenylene terephthalamide)( PPTA) was investigated for the purpose of obtaining products with better performance. PPTA fiber subjected to heat treatment under...The relationship between property and structure of poly( p-phenylene terephthalamide)( PPTA) was investigated for the purpose of obtaining products with better performance. PPTA fiber subjected to heat treatment under different conditions was intensively studied. Simultaneous wide-angle X-ray diffraction( WAXD) technique was introduced to study the changes of crystal structure. It was found that the tensile modulus was strongly sensitive to the levels of temperature and tension. The structure parameters including crystal size and crystal orientation after heat treatment evolve similarly to the tensile modulus,indicating a direct structure-property relationship. The lattic c-dimension increases after heat treatment and is greatly affected by the tension. An optimal temperature can be found around 400 ℃,where big change can happen in the crystal structure due to α-relaxation in the crystal region as supported in dynamic mechanical analysis( DMA).展开更多
Poly（p-phenylene） （PPP） films have been electrochemically deposited on mirrorlike stainless steel （SS） electrode surfaces by direct oxidation of benzene in boron trifluoride diethyl etherate （BFEE） solutions a...Poly（p-phenylene） （PPP） films have been electrochemically deposited on mirrorlike stainless steel （SS） electrode surfaces by direct oxidation of benzene in boron trifluoride diethyl etherate （BFEE） solutions at a constant applied potential of 1.7 V （versus Ag/AgCl）. The chain conformations of as-grown PPP films have been studied by Raman spectroscopy. The results demonstrated that high synthesis temperature favors the formation of planar PPP, and the conformation of planar PPP can be changed into torsional PPP by cooling treatment.展开更多
基金the National Natural Science Foundation of China(Nos.52073224 and 52202111)the Textile Vision Basic Research Program of China(No.J202110)+4 种基金the Key Research and Development Program of Xianyang Science and Technology Bureau,China(No.2021ZDYF-GY-0035)the Key Research and Development Program of Shaanxi Province,China(No.2022SF-470)the Key Research and Development Program of Shaanxi Province,China(No.2022GY-377)the Natural Science Foundation of Shaanxi Province(No.2021JQ-685)the Scientific Research Project of Shaanxi Provincial Education Department,China(No.22JC035).
文摘Conventional firefighting clothing and fire masks can protect firemen’s safety to a certain extent,whereas cannot perceive environmental hazards and monitor their physical status in real time.Herein,we fabricated two kinds of Janus graphene/poly(pphenylene benzobisoxazole)(PBO)fabrics by laser direct writing approach and evaluated their performance as intelligent firefighting clothes and fire masks.The results showed that the Janus graphene/PBO fabrics were virtually non-combustible and achieved the highest thermal protection time of 18.91 s ever reported in flame,which is due to the intrinsic flame-retardant nature of PBO fibers.The graphene/PBO woven fabrics-based sensor showed good repeatability and stability in human motion monitoring and NO_(2)gas detection.Furthermore,the piezoelectric fire mask was assembled with graphene/PBO nonwoven fabric as electrode layer and polyvinylidene fluoride(PVDF)electrostatic direct writing film as piezoelectric layer.The filtration efficiency of the fire mask reaches 95%for PM_(2.5)and 100%for PM_(3.0),indicating its effective filtration capability for smoke particles in fires.The respiratory resistance of the piezoelectric fire mask(46.8 Pa)was lower than that of commercial masks(49 Pa),showing that it has good wearing comfort.Besides,the piezoelectric fire mask can be sensitive to the speed and intensity of human breathing,which is essential for indirectly reflecting the health of the human body.Consequently,this work provides a facile approach to fabricate next-generation intrinsic flame-retardant smart textiles for smart firefighting.
文摘A series of soluble poly(p-phenylene vinylene) (PPV) derivatives were synthesized through dehydrochlorination with the p-metaoxy phenol as starting materials. The electronic characteristics of PPV derivatives were studied.
基金financially supported by the National Natural Science Foundation of China(Nos.U1463208 and 91334201)
文摘A non-aqueous suspension polycondensation method was proposed to proceed the reaction ofp-phenylenediamine and terephthaloyl chloride for the preparation of poly（p-phenylene terephthalamide） （PPTA）. The system was operated with NMP-CaCI2 solution as the dispersed phase and inert liquid paraffin as the continuous phase. Each of NMP-CaCl2 solution microdroplet suspended in paraffin served as a microreactor where the polycondensation took place. According to the results of TGA, XRD, IR, SEM and EA, PPTA with good quality was obtained through this novel method, and a number of main factors influencing this process were investigated to determine the optimum condition for the preparation of PPTA. Besides, this two-phase polycondensation system brings many unique advantages compared to the conventional solution polycondensation method, including a sealed reaction environment keeping the reactants away from oxygen and water, easy removal of HCI to promote the reaction, well-controlled temperature and low viscosity which means less energy cost.
基金financially supported by the National Science Fund for Distinguished Young Scholars (No.50925311)the National Natural Science Foundation of China (No.20976112)
文摘Poly（phenylene sulfide） （PPS） with different crosslinking levels was successfully fabricated by means of high- temperature isothermal treatment （IT）. The crosslinking degree of PPS was increased with IT time as revealed by Fourier-transform infrared spectroscopy and dynamic viscosity measurements. Its influence on the non-isothermal crystallization behaviors of PPS was studied by differential scanning calorimeter （DSC）. The crystallization peak temperature of PPS with 6 h IT was 15 K higher than that of the one with 2 h IT at 30 K/min cooling rate. The non-isothermal crystallization data were also analyzed based on the Ozawa model. The Ozawa exponent m decreased from 3.5 to 2.2 at 232~C with the increase of the IT time, suggestive of intensive thermal oxidative crosslinking reducing the crystallite dimension as PPS crystal grew. The reduced cooling crystallization function K（T） was indicative of the larger activation energy of crosslinked PPS chain diffusion into crystal lattice, resulting in a slow crystal growth rate. Additionally, the overall crystallization rate of PPS was also accelerated with the increase of crosslinking degree from the observation of polarized optical micrograph. These results indicated that the chemical crosslinked points and network structures formed during the high-temperature isothermal treatment acted as the effective nucleating sites, which greatly promoted the crystallization process of PPS and changed the type of nucleation and the geometry of crystal growth accordingly.
基金The authors acknowledge the financial support obtained from the National Key Research and Development Program of China(2020YFB1312902)the National Natural Science Foundation of China(21975281)The authors are also grateful for the technical support for Nano-X from Suzhou Institute of Nano-Tech and Nano-Bionics,Chinese Academy of Sciences(SINANO).
文摘Today the developed yarn muscles or actuators still cannot satisfy the requirements of working in high-temperature environ-ments.Thermal resistivity is highly needed in aerospace and industrial protection applications.Herein,an artificial muscle with high-temperature tolerance is prepared using carbon nanotube(CNT)wrapped poly(p-phenylene benzobisoxazole)(PBO)composite yarns.A thermal twisting method was utilized to reorientate the stiff PBO molecular chains into a uniform and twist-stable coiled structure.The CNT/PBO composite yarn muscle generates reversible contractile strokes up to 18.9%under 5.4 MPa tension and outputs 1.3 kJ kg^(-1) energy density.In contrast to previous actuators,which are normally oper-ated at room temperatures,the CNT/PBO composite yarn muscles can work at ambient temperatures up to 300℃ with high contractile stroke and long-term stability.A bionic inchworm robot,a deployable structure,and smart textiles driven by the high-temperature-tolerant yarn muscles were demonstrated,showing the promise as a soft actuator towards high-temperature environment applications.
基金This work was supported by National Natural Science Foundation of China(NSFC)(Nos.20804008,20974038,50973039,and 20921003)National Program on Key Basic Research Project(973 Program)(Nos.2007CB936402 and 2009CB939701)the China Postdoctoral Science Foundation(No.20090450139).
文摘Materials with emission over the whole visible range(400-800 nm)have been obtained through incorporating single-colored CdTe nanocrystals(NCs)into a poly(p-phenylene vinylene)(PPV)precursor[the sulfonium polyelectrolyte precursor of PPV].Firstly,the quantum yield(QY)of the PPV precursor was improved to~50%via heat treatment of a mixed solution of the PPV precursor and poly(vinyl alcohol)(PVA)at 100°C for 3 min.Then,single-colored CdTe NCs were incorporated into the mixed solution.The introduction of the PVA was necessary to reduce the electrostatic interaction between the PPV precursor and CdTe NCs,which improved their compatibility.The reduced electrostatic interaction eliminated Förster resonance energy transfer(FRET)processes between NCs,as well as between NCs and the PPV precursor,which allowed the functional integration of the polymer and NCs.Consequently,polymer/NC composites with almost any Commission Internationale de L’Eclairage(CIE)coordinates can be achieved by simply changing the size and amount of the NCs.In particular,when the emission wavelength of the CdTe NCs was 559 nm,a pure white-light emitting material with CIE coordinates(0.337,0.332)was obtained.
基金This research was supported, in part, by grants from the National Science Foundation (NSF-DMR Intemational Program 96-16255 (F. R. and P. H. G.) and NSF-DMR Polymer Program 93-12823 and 96-16255 (J. Y., G. S., J. L. and P. H. G.)) and Grant Agency of the
文摘The morphology and crytal structure of poly(p-phenylene terephthalate) (PPT), prepared by confined thin filmmelt (CTFMP) and solution (CTFSP) and bulk solution polymerization, were characterized by transmission electronmicroscopy, electron dimaction and molecular modeling. The unit cell is monoclinic (P2_1/a space group) with parameters a =7.89, b = 5.49, c = 12.65 A, α=γ= 90°, β=100.33°, density = 1.48 g/cm^3, the a, b and β values differing slightly from thosereported previously in the literature. A degree of variation in relative intensities of hk0 reflections in, apparently, untilted[001] ED patterns was observed from a given sample, suggesting some variation in molecular packing. ED evidence wasfound for a second phase, with [001] appearing the same as for phase Ⅱ of the related poly(p-oxybenzoate) (PpOBA)polymer. CTFMP crystals polymerized above 220℃ (up to 370℃) and CTFSP crystals polymerized at 300℃ consisted oflamellae 100-200 A thick.
基金supported by the Centennial Fund of Chula-longkorn UniversityAssoc.Prof. Mana Sriyuthsak for his suggestive and academic support insensor fabricationfinancial support from University of Pembangunan Nasional "Veteran" Yogyakarta, Indonesia
文摘Dispersion of multi-walled carbon nanotubes in poly（p-phenylene） composite exposed to toluene was experimentally investigated. 3 mg of multi-walled carbon nanotubes with nominal size of 20 nm was compounded with 30 mg of poly（p-phenylene） with the presence of terpineol as binding initiator. To investigate an optimal condition for homogenizing all constituents, ultrasonication with an output power of 750W was employed with compounding time of 3, 10, 20 and 30 min. With FTIR analyses, it could be confirmed that homogeneous composite of multi-walled carbon nanotubes and poly（p-phenylene） could be prepared. SEM analyses were also conducted to examine the dispersion of multi-walled carbon nanotubes in the polymer matrix. Then intrinsic electrical resistance of the composites after being exposed to toluene was also investigated. It was found that the composite film prepared with ultrasonication for 20 min could provide sufficiently sensitive response with respect to varied concentration of toluene.
文摘Commercial poly(p-phenylene sulfide) (PPS) was thermally cured, which resulted in an increase of molecular weight due to cross-linking. Non-isothermal crystallization studies of samples cured for up to 7 days at 250?C showed a monotonous increase of crystallization temperature compared to pure PPS. However, a further increase of curing time decreased the crystallization temperature. The change in the half-crystallization time (t1/2) was similar to the crystallization temperature. Thus, the cross-linking of PPS affected crystallization behaviors significantly. To a certain extent, crosslinks acted as nucleation agents, but excessive cross-linking hindered the crystallization. Morphologies observed by polarized optical microscopy suggested that thermal curing for as little as 1 day contributed to the spherulitic structure having a smaller size, that was not observed with pure PPS.
文摘High viscous PPTA copolymer is prepared by low temperature solution copolycondensation of terephth-aloylchloride, p-phenylenediamine and p, p'-diamino-phenylpiperazine in the NMP-CaCl2 solvent system. The inherent viscosity of all copolymers is more than 5. If more quantity of 3rd monomer is introduced into the macromolecular chain, the inherent viscosity becomes higher. The copolymer's ash content is less than 1000 μg/g. The heat durability of copolymer is close to that of PPTA, and its dissolubility is superior to that of PPTA.
文摘The morphology of PPTA pulp is investigated by means of optical microscope and scanningelectron microscope (SEM). It shows that PPTA pulp has feather-like branch, needle point-likeend, and irregular cross-section, which are very important for PPTA pulp as a reinforcer. Theseparation limitation of PPTA pulp is also investigated from both torn and brittle break cross-sec-tion. A packing mechanism is proposed to illustrate the microfibril packing in the gel system.
基金financially supported by the National Natural Science Foundation of China (Nos.21204011,51603120 and 21404023)the National Basic Research Program of the China 973 Program (No.2011CB606101)+1 种基金Fundamental Research Funds for the Central Universities,Innovation Program of Shanghai Science and Technology Commission (No.14521100605)the Innovation Program of Shanghai Municipal Education Commission
文摘The conventional low-temperature method of solution polycondensation was developed to realize the reaction of p-phenylenediamin and terephthaloyl chloride for the preparation of poly（p-phenylene terephthalamide）（PPTA）. Some main factors influencing this process were investigated to determine the optimum condition for high molecular weight. Experiment showed significant slowing of the reaction and gradual deviation of second-order reaction kinetics due to diffusion control. These phenomena were studied theoretically via dynamic Monte Carlo simulation. A concise expression,n～c0^-0.88·t^0.37, was proposed to describe the diffusioncontrolled polycondensation process as a function of the monomer concentration and reaction time. The theoretical results provided a good description of diffusion-effected kinetics for the polycondensation process of PPTA, and demonstrated good agreement with the experimental data. Some differences of scaling relations between model and experiment results were also discussed.
基金Project supported by the State Science and Technology Commission and the National Natural Science Foundation of China.
文摘The ab initio crystal orbital calculations on conjugated aromatic six-membered rings polymers, namely, poly(p-phenylene) (PPP), poly(2,5-pyridinediyl) (PPD), poly(2,5-phosphabenzene) (PPB) and ploy(2,5-arsabenzene) (PAB) are reported. The comparison of the important electronic properties of these polymers, such as band gap, bandwidth, ionization potential and electron affinity, indicates that PPP is the best intrinsic semiconductor, and PPD has the best prospects for forming n-doped conducting materials.
基金Supported by the National Natural Science Foundation of China（No.51173155）.
文摘This paper deals with the relationships between the structure of poly（p-phenylene vinylene）（PPV） film and treatment temperature and their mechanical properties.The chemical structures and aggregated structures of PPV precursor（PPVpre） and PPV treated at three node temperatures（125,155 and 230 ℃） were investigated by FTIR spectrometry and X-ray diffraction.The results show that the content of trans-conformation and the size of the crystalline domains increased with the increase of treatment temperature.The mechanical performances of the corresponding polymers were studied by nanoindentation.The elastic modulus and hardness of PPV films decreased with the increases of the content of trans-conformation and the size of the crystalline domains.These results suggest that the conformation and the size of the crystalline domains are able to induce the elastic modulus and hardness variation of PPV films.
基金This project was supported by the National Basic Research Project-Macromolecular Condensed State, the National Natural Science Foundation of China and US-China Cooperative Research Program of NSF.
文摘The conformation, the chain packing stabilization and the unit cell modeling of poly(p-phenylene benzobisthiazole) have been investigated by using molecular simulation techniquein the present work. A coupling behaviour of σ-bond rotations at either side of the pheny-lene ring or the heterocyclic ring was found surely to exceed a length of the repeat unit ofthe polymer chain. For a single chain model, the stable torsion angle of the repeat resultedat 14°. In the crystalline cell minimization, the dihedral angle along the polymer chaincould even be stabilized in various values. It therefore indicates that the intermolecularinteraction does play a considerable role for this polymer forming the conformation. Ac-cording to cohesive energies calculated for these unit cell models, the torsion angle in themost stable crystalline cell is 0°. When the chains packing together, there exist so manyenergy stable wells along the chain axis 0.35--0.36nm apart from neighbouring chains.Most of the unit cells have quite closed cohesive energies. These factors thus cause thedifficulty of forming an unique perfect crystalline structure of the polymer. The presentstudy suggested a number of reasonable unit cells, and the most stable crystalline structurefor this polymer that is monoclinic, non-primitive unit cell.
基金National Basic Research Program of China(973 Program)(No.2011CB606103)National High-Tech Research and Development Program of China(863 Program)(No.2012AA03212)the Fundamental Research Funds for the Central Universities,China(No.11D10625)
文摘The relationship between property and structure of poly( p-phenylene terephthalamide)( PPTA) was investigated for the purpose of obtaining products with better performance. PPTA fiber subjected to heat treatment under different conditions was intensively studied. Simultaneous wide-angle X-ray diffraction( WAXD) technique was introduced to study the changes of crystal structure. It was found that the tensile modulus was strongly sensitive to the levels of temperature and tension. The structure parameters including crystal size and crystal orientation after heat treatment evolve similarly to the tensile modulus,indicating a direct structure-property relationship. The lattic c-dimension increases after heat treatment and is greatly affected by the tension. An optimal temperature can be found around 400 ℃,where big change can happen in the crystal structure due to α-relaxation in the crystal region as supported in dynamic mechanical analysis( DMA).
基金This work was supported by the National Natural Science Foundation of China(Nos.20374034,50225311).
文摘Poly（p-phenylene） （PPP） films have been electrochemically deposited on mirrorlike stainless steel （SS） electrode surfaces by direct oxidation of benzene in boron trifluoride diethyl etherate （BFEE） solutions at a constant applied potential of 1.7 V （versus Ag/AgCl）. The chain conformations of as-grown PPP films have been studied by Raman spectroscopy. The results demonstrated that high synthesis temperature favors the formation of planar PPP, and the conformation of planar PPP can be changed into torsional PPP by cooling treatment.
