CRYSTAL STRUCTURE AND MORPHOLOGY OF NASCENT SAMPLES OF SYMMETRIC AROMATIC POLYESTERS——Ⅰ.POLY(P-PHENYLENE TEREPHTHALATE)

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.

CRYSTAL STRUCTURE AND MORPHOLOGY OF NASCENT SAMPLES OF SYMMETRIC AROMATIC POLYESTERS——Ⅱ. POLY(p-PHENYLENE 2,6-NAPHTHALATE)

Confined thin film melt polymerization (CTFMP) of naphthalene chloride/hydroquinone (NCMQ, 1/1, molar)mixtures at polymerization temperatures (T_p) below ca. 300℃ resulted in relatively thick, elongated crystals. Polymerizationof NC/HQ above 300℃ between glass yielded well-formed lamellar crystals ca. 100 A thick. Phase Ⅰ and Ⅱ [001] EDpatterns were obtained for all T_p, the relative amount of phase Ⅰ increasing with T_p. Polymerization of naphthalenedicarboxylic acid/hydroquinione diacetate 1/1 mixtures at high T_p also yielded lamellar crystals that "curled up" off of thesubstrate. When the high temperature CTFMP polymerization was conducted between mica, aggregates of lamellae on-edgedeveloped but epitaxial growth did not occur. Epitaxial growth of lamellae between mica could be obtained, however, byconfined thin film solution polymerization, with both of the latter samples yielding apparently related ED patterns from adifferent unit cell than phase Ⅰ or Ⅱ. Fiber patterns, obtained from sheared samples, indicated considerably greater crystaldisorder than in the nascent crystals. Refinement of the phase Ⅰ unit cell parameters, based on the [001] and [01 1] EDpatterns, with modeling based on Cerius^2, suggests a monoclinic phase Ⅰ unit cell with a = 7.76, b = 5.71, c = 14.99 A, α = γ= 90°, β= 99.7°, ρ = 1.47 g/cm^3, space group P12_1/al.

Mechanical Property and Crystal Structure of Poly(p-phenylene terephthalamide)(PPTA) Fibers during Heat Treatment under Tension

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).

A STUDY OF PACKING STRUCTURE OF POLY(P-PHENYLENE BENZOBISTHIAZOLE)BY MOLECULAR SIMULATION

Molecular simulation technique was used in an examination of the possibilities of chain packing in the crystalline state for poly(ρ-phenylene benzobisthiazole).It has been found that one reason of hardly forming very ordered crystal of the polymer is the existence of so many stable positions of interchain interaction along chain axis.

The Synthesis and Electronic Characteristics of Poly(p-Phenylene Vinylene) Derivatives

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.

Effects of poly-(p-phenylene terephthamide) powder coated with polydopamine on ethylene-propylene-diene-terpolymer grafted maleic anhydride

In this paper, we report a technique for the surface modification of poly-(p-phenylene terephthamide)(PPTA) powder coated with polydopamine(PDOPA). We used air oxidation to self-polymerize dopamine(DOPA) to ensure that the PPTA powder was coated. Our results indicate that the modified surface of PPTA powder enhances compatibility with the polymer matrix without damaging its structure. Additionally, it is possible to control the coating thickness of PDOPA by regulating the reaction time. The modified PPTA powder improved the comprehensive property of ethylene-propylene-diene-terpolymer grafted maleic anhydride(EPDM-g-MAH), and it proved that this method can enhance the strength and electric insulativity of EPDM-g-MAH.

Laser-induced Janus graphene/poly(p-phenylene benzobisoxazole)fabrics with intrinsic flame retardancy as flexible sensors and breathable electrodes for fire-fighting field

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.

Effect of Curing Poly(<i>p</i>-Phenylene Sulfide) on Thermal Properties and Crystalline Morphologies

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.

STUDIES ON THE POLYPYRROLE/POLYELECTROLYTE MOLECULAR COMPOSITES

The potyelectrolyte of propane sulfonate(PS) grafted PPTA copolymers——PPTA-PS, PPTA[O]-PS, PPTA[C]-PS were prepared and used as electrolyte in the process of electrochemical polymerization of pyrrole to form the molecular composite polypyrrole (PPY)/Polyelectrolyte.The preparation and liquid crystalline property of three kinds of polyelectrolyte, the electrical conductivity, mechanical properties, SEM and thermoproperties of PPY/polyelectrolyte are presented in detail.

RAMAN SPECTROSCOPIC STUDY ON THE CHAIN CONFORMATION OF ELECTROSYNTHESIZED POLY(ρ-PHENYLENE)FILMS

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.

CONFORMATION AND CHAIN PACKING STRUCTURES OF POLY (ρ-PHENYLEN BENZOBISTHIAZOLE) BY MOLECULAR SIMULATION

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.

聚芳酰胺纳滤膜可控制备及其对染料废水分离性能研究

随着纳滤膜应用领域的不断扩大,多孔基膜的性能和表面聚酰胺层的结构成为影响纳滤膜分离性能的关键因素。与传统多孔基膜相比,聚对苯二甲酰对苯二胺(PPTA)多孔基膜是一种新型高性能聚芳酰胺材料,具有优异的亲水性、热稳定性和耐酸碱性,是一种理想的膜材料。本研究通过在水相单体溶液中添加金属有机框架UiO-66-NH_(2)颗粒,研究UiO-66-NH_(2)的添加量在界面聚合过程中对PPTA多孔基膜表面聚酰胺层结构的影响,并探究所得表面结构对染料废水渗透/分离性能的影响。实验结果表明,当水相单体溶液中加入1.3g/L UiO-66-NH_(2)时,所得PPTA杂化复合纳滤膜表面呈现纳米条纹状结构。将其用于亚甲基蓝(MB)染料/无机盐分离,与未添加UiO-66-NH_(2)的纯PPTA纳滤膜相比,PPTA杂化复合纳滤膜对MB截留率高达98.2%,渗透通量19.79L/m^(2)·h·MPa,表现出优良的渗透/分离性能。

日光老化及海水老化对PPTA纤维结构及性能的影响

通过日光老化、海水老化及日光/海水复合老化实验,研究了不同老化方式及老化时间对聚对苯二甲酰对苯二胺(PPTA)纤维表面形貌、化学结构、结晶结构及力学性能的影响。结果表明:随日光老化时间延长,PPTA纤维表面逐渐劣化,分子链中酰胺键发生断裂,结晶度和晶粒尺寸下降,结晶结构被破坏,力学性能呈现先慢后快的下降趋势,日光老化35 d后PPTA纤维的断裂强度和断裂伸长率保留率分别为73.7%和69.2%;海水老化35 d后PPTA纤维表面产生深度较浅的纵向沟壑,大部分集中在纤维皮层;复合老化35 d后PPTA纤维表面纵向沟壑较日光老化35 d时更深,逐渐向PPTA纤维芯层深入;海水老化35 d后纤维的断裂强度和断裂伸长率保留率分别为63.0%和72.4%,日光/海水复合老化35 d后纤维断裂强度和断裂伸长率保留率分别为58.7%和65.9%。

Non-aqueous Suspension Polycondensation in NMP-Ca Cl_2/Paraffin System―A New Approach for the Preparation of Poly(p-phenylene terephthalamide)

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.

烷基取代聚对苯二甲酰对苯二胺的相对分子质量以及相对分子质量分布分析

聚对苯二甲酰对苯二胺(PPTA)的相对分子质量和相对分子质量分布直接影响芳纶纺丝性能。PPTA主链间的氢键作用使其难溶于氯仿等常用有机溶剂中,不能满足核磁共振波谱仪、质谱和凝胶渗透色谱法等测试要求。为了提高PPTA的溶解性,通过主链上N位接枝系列不同种类和取代程度的烷基侧链,得到可溶解的烷基化PPTA,考察了不同烷基种类和烷基化条件对相对分子质量以及相对分子质量分布的影响。乙基烷基化PPTA的取代程度可达98.6%,有利于得到多分散系数较低和更为准确的相对分子质量分布。根据马克霍温克方程,得到了特定黏度范围内重均相对分子质量与特性黏数的关系公式为[η]=9.96×10^(-3)M_(w)^(1.08),对优化PPTA合成条件和改善芳纶纤维的性能提供了参考。

PPTA回收溶剂NMP中PPD残留量的测定

采用反相高效液相色谱法测定聚对苯二甲酰对苯二胺(PPTA)回收溶剂N-甲基吡咯烷酮(NMP)中对苯二甲酰氯与对苯二胺(PPD)的残留量,探讨了高效液相色谱仪的色谱条件,并研究了分析方法的精密度、准确度、检出限。结果表明:采用反相高效液相色谱法测定回收溶剂NMP中PPD的含量,适宜的色谱条件为色谱柱采用十八烷基硅烷键合硅胶柱,流动相中水/改性剂(体积比为991)与乙腈体积比为955,紫外波长为280 nm,进样量为10μL;该分析方法精密度优、重复性好、线性方程的相关性好,相对标准偏差为0.85%,加标回收率为98.1%~101.1%,检出限为0.35μg/g,能满足PPTA回收溶剂NMP中微量PPD含量的测定需求。

Dispersion of multi-walled carbon nanotubes in poly(p-phenylene) thin films and their electrical characteristics

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.

Kinetics Analysis on the Polycondensation Process of Poly(p-phenylene terephthalamide):Experimental Verification and Molecular Simulation

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.

聚对苯二甲酰对苯二胺多孔膜的制备及表征

以浓硫酸为溶剂,聚乙二醇(PEG)为致孔剂,采用溶液相转化法制备了聚对苯二甲酰对苯二胺(PPTA)多孔平板膜,考察了膜的纯水通量、力学强度、截留率等性能,并用场发射扫描电子显微镜观察膜形貌。结果表明,所得PPTA多孔膜为具有不对称结构的非均质膜,上表面(自由面)为致密层,下表面(玻璃板面)为多孔层,可观察到原纤化微孔结构,膜横截面存在典型的溶出指状孔。随PPTA含量降低、致孔剂相对分子质量和凝固浴温度提高,膜通透性均随之相应有所提高。PPTA多孔膜对卵清蛋白溶液截留率达90%以上,对油水乳化液截留率可达70%以上。

对位芳香族聚酰胺多孔膜制备及性能研究

以浓硫酸为溶剂,以聚乙二醇(PEG)、聚乙烯吡咯烷酮(PVP)为致孔剂,以二氧化硅(SiO2)无机粒子为添加剂,采用溶液相转化法制备了聚对苯二甲酰对苯二胺(PPTA)多孔平板膜,考察了膜的纯水通量、孔隙率、力学性能、热稳定性等性能,并用场发射电子扫描显微镜(FESEM)观察了膜表面形貌.结果表明:所得PPTA多孔膜为具有不对称结构的非均质膜,随着无机粒子SiO2含量提高、致孔剂混合、凝固浴温度的增加,膜渗透性能增大;膜力学性能随SiO2含量提高而提高,最大断裂强度可达1.5 MPa,断裂伸长率由7%增大到14%左右;而热稳定性随SiO2含量提高无明显变化,热分解温度均可达400℃以上.