苯并双噁唑类聚合物的合成

详细介绍了以4,6-二氨基间苯二酚盐酸盐(DADHB)为原料,采用多聚磷酸法、三甲基硅烷基化法、中间相聚合法、单体成盐法合成聚对苯撑苯并双噁唑(PBO),还有以4,6-二硝基间苯二酚(DNR)为原料,先选择还原制得4-氨基-6-硝基间苯二酚盐酸盐,进而与对甲氧羰基苯甲酰氯进行缩环合获得苯并噁唑化合物,再催化加氢合成AB型PBO新单体2-(对甲氧羰基苯基)-5-氨基-6-羟基苯并噁唑,最后自缩聚反应制备PBO的新路线.另外,本文还介绍了直链烯烃型、直链脂肪烷烃型、稠环芳烃型、联苯取代基型、杂环型、聚醚型等苯并双噁唑类聚合物的合成方法.     

聚亚苯基苯并二噁唑缩聚反应动力学

以4,6-二氨基间苯二酚磷酸盐(DAR.2HP3O4)和对苯二甲酸(TA)为原料经非均相逐步缩聚反应制得聚亚苯基苯并二噁唑(PBO)。该反应可分为溶解控制(齐聚合)、反应动力学控制(预聚合)以及高分子链段扩散控制(后聚合)3个阶段。探讨了各阶段的反应过程,并对PBO预聚合反应动力学进行了研究。结果表明:其动力学符合不可逆二级反应机理,反应活化能为51.9 kJ/mol。     

苯并唑类共聚物与共混物的能量转移与激子空间限制研究

通过3-氨基-4-羟基苯甲酸盐酸盐(AHBAH),2,5-二氨基-1,4-苯硫醇盐酸盐(DABDT)和2,5-噻吩二羧酸(TDA)在多聚磷酸中缩聚,合成了一系列不同组成的高、低带隙无规共聚物聚(2,5-苯并噁唑)-co-聚(2,5-噻吩基苯并二噻唑)(ABPBO-co-PBZTT),并制备了一系列由ABPBO和PBZTT组成的共混物.通过紫外-可见吸收光谱、光致荧光光谱研究了聚合物不同组成和结构变化对光物理性能的影响.随着共聚物中PBZTT含量的增加,共聚物的发射波长红移,并发生了明显的ABPBO结构吸收能量向PBZTT转移的现象,共聚物膜的量子效率比纯PBZTT膜的量子效率有明显提高.共混物虽然也发生了能量转移现象,但其更易于形成集聚体,量子效率与纯的PBZTT聚合物相比,并没有明显提高.     

抗紫外老化聚对苯撑苯并二噁唑(PBO)纤维的制备与表征

通过化学添加2,5-二羟基对苯二甲酸(DHTA)共聚,以及添加金红石型纳米TiO2物理共混的方法,制备了聚对苯撑苯并二噁唑(PBO)的抗紫外改性纤维.考察了纤维的力学性能、特性粘度及表面形貌在紫外老化过程中的变化,并结合PBO纤维紫外加速老化后的红外分析,对PBO纤维的光老化机理进行了初步研究.结果表明,本实验所制备的DHPBO纤维以及DHPBO/n-TiO2纤维的抗紫外老化能力明显高于PBO纤维,并且金红石型纳米TiO2对PBO的抗紫外改性效果要优于有机紫外吸收剂(2,2'-(1,2-乙烷二基)双(4,1-亚苯基)双苯并噁唑).     

聚苯并双噁唑酰亚胺的热分解动力学研究

采用二步法合成了以2,6-二(对-氨基苯)苯[1,2-d;5,4-d’]二噁唑和1,4-二(3,4-二苯氧基)苯四甲酸二酐(HQDPA)为单体的聚苯并双噁唑酰亚胺.该聚酰亚胺的预聚体聚酰胺酸的黏度为1.70 dL/g,经过热环化后能够生成浅黄色的聚酰亚胺薄膜.通过热重分析法研究了聚苯并双噁唑酰亚胺在N2气氛中的热降解机理.采用Flynn-Wall-Ozawa和Friedman法计算了聚苯并双噁唑酰亚胺热降解表观活化能,分别为356.36kJ/mol和370.54 kJ/mol,平均值为363.45 kJ/mol;反应级数为4.22,指前因子为6.44×1016s-1.采用Coast-Redfern法和Phadnis-Deshpande法研究了聚苯并双噁唑酰亚胺的热降解固相反应机理,认为该聚酰亚胺的热降解机理属于反曲线(A3)机理,是成核和增长模式(Avrami equation 2方程)控制的热降解反应,积分形式为g(X)=[-ln(1-X)]3.     

2-苯基苯并噁唑的光解反应

聚对苯撑苯并二噁唑(PBO)纤维对光较为敏感,在紫外光照射下会发生降解.本文研究了该纤维的单体2-苯基苯并噁唑(PO)的初级光化学反应机理.当PO分子吸收一个光子而跃迁到第一激发态后,克服25.59kJ·mol-1能垒而越过过渡态,此时噁唑环打开,且两个苯环形成大约90°的二面角而得到产物,该产物可进一步与空气中的水发生次级反应.计算结果表明在第一激发态上噁唑开环反应很容易,但在基态势能面并没有发现噁唑的开环路径.分子中的原子(AIM)的计算结果与上述分析过程相吻合.     

共轭刚性苯并二噁唑类聚合物的合成及其光物理性能研究

设计并合成了一系列共轭高分子———聚亚苯基苯并二唑 (PBO) ,聚亚乙烯基苯并二唑 (PBOV)和聚亚丁二唑 (PBODV) ,并对它们进行了表征 .用紫外吸收光谱和荧光光谱对聚合物的溶液和薄膜进行了详细的研究 ,研究结果表明分子结构中双键的引入可以降低聚合物的光带能隙 ,λmax从PBO溶液的 4 2 8 5nm (Eg=2 76eV) ,到PBOV溶液的 4 80 5nm (Eg=2 4 6eV) ,再到PBODV溶液的 4 96 0nm (Eg=2 38eV) .共轭程度的增加使得聚合物溶液更容易发生集聚从而导致荧光自熄灭 .     

含烷基侧链聚芴基苯并二噁唑聚合物的合成及性能研究

通过溶液缩聚的方法合成了一种含烷基侧链聚芴基苯并二噁唑聚合物(PBOPFx),讨论了聚合物的光物理性能、热性能和溶解性能.结果表明,在甲基磺酸(MSA)溶液中,PBOPFx紫外吸收显示出最大吸收峰为466 nm左右的蓝光发射,与PBO相比,最大紫外吸收峰和最大荧光发射峰均发生了明显红移,这是由于芴单元的引入,提高了聚合物的共轭程度,加强了对电子的束缚能力.此外,比较了PBOPFx在320 nm处和430 nm处激发得到的荧光发射光谱,预测聚合物中存在两种共轭单元,通过测定氧化还原曲线以及讨论stokes位移,验证了这个假设,但是由于两种共轭单元并没有出现明显的分离现象,同时还伴有电子传输杂化,致使PBOPFx主要显示出共轭长度大的单元的吸收和发射.另外由于芴单元中烷基侧链的存在,聚合物(PBOPFx)的热稳定性远低于聚亚苯基苯并二噁唑聚合物(PBO),起始分解温度在350℃左右,溶解性方面,PBOPFx有了很大的改善,在大多数有机溶剂中能较好溶解.     

2-(ω-联苯基多亚甲基)-5-联苯基噁唑-1,3和2-(ω-联苯基多亚甲基)-5-联苯基噁二唑-1,3,4的合成

继2,6-二取代苯并二噁唑、2,5-二取代噁唑和2,5-二取代噁二唑及1,4-二(苯并噁唑-1,3基-2)苯等系列化合物合成及光性能研究后,又合成了双荧光发色团化合物2-(ω-联苯基多亚甲基)-5-联苯基噁唑-1,3和2-(ω-联苯基多亚甲基)-5-联苯基噁二唑-1,3,4共七种化合物。     

2-(2′-苯基丙烯基)苯并噁唑类化合物的合成及晶体结构

合成了11种2-(2′-苯基丙烯基)苯并噁唑类和9种2-(2′-苯基丙烯基)-5-甲基苯并噁唑类化合物。测定了它们的熔点、元素分析、红外光谱及个别衍生物的核磁共振谱和X射线单晶分析,确证了这类化合物的分子结构。     

Improvement of surface wettability and interfacial adhesion ability of poly(p-phenylene benzobisoxazole) (PBO) fiber by incorporation of 2,5-dihydroxyterephthalic acid (DHTA)

By introducing 2,5-dihydroxyterephthalic acid (DHTA) into poly(p-phenylene benzoxazole) (PBO) macromolecular chains, dihydroxy poly(p-phenylene benzobisoxazole) (DHPBO) was synthesized and then DHPBO fibers were prepared by dry-jet wet-spinning method. Effects of hydroxyl polar groups on surface wettability and interfacial adhesion ability of PBO fiber were investigated. With the incorporation of double hydroxyl polar groups, contact angle on PBO fiber for water can decrease from 71.4° to 50.70°, and contact angle for ethanol can decrease from 37.2° to 27.40°. The wetting time on DHPBO fibers for water can be as short as 650 ms, which is half of that of PBO fibers. The interfacial shearing strength (IFSS) between DHPBO (10% mol content DHTA) fibers and epoxy resin is 18.87 MPa, 92.55% higher than that of PBO fibers. SEM images indicate that the PBO/epoxy composite failure mode may change from fiber/matrix adhesive failure to partially cohesive failure.     

主链含羟基的芳杂环液晶共聚物聚对苯撑苯并二噁唑的 合成及性能研究

通过在聚合过程中添加少量2,5-二羟基对苯二甲酸(DHTA)部分替代对苯二甲酸(TPA)与4,6-二氨基间苯二酚(DAR)盐酸盐进行共聚, 合成了一系列大分子链上含有羟基基团的DHPBO共聚物, 并制得其初生纤维. 利用FTIR、接触角等分析手段对其化学结构和纤维表面性能进行了表征, 通过单丝拔出实验和SEM考察了DHPBO纤维与环氧树脂基体的界面剪切强度, 并采用轴向压缩弯曲实验和紫外光加速老化实验评价了羟基基团的引入对提高纤维压缩性能和抗紫外性能的影响. 结果表明, 羟基基团的引入使得DHPBO纤维的表面亲水性、与环氧树脂的界面剪切强度以及纤维的压缩性能和抗紫外性能都有了显著提高.     

Synthesis and Characterization of Poly(p-phenylene benzobisoxazole)/Poly(pyridobisimidazole) Block Copolymers

Poly(p-phenylene benzobisoxazole)/poly(pyridobisimidazole) block copolymers (PBO-b-PIPD) were prepared by introducing poly(pyridobisimidazole) (PIPD) moieties into the main chains of poly(p-phenylene benzobisoxazole) (PBO) in order to enhance its photostability. PBO and copolymer fibers were directly prepared from the polymerization solutions by dry-jet wet-spinning. Chemical structures and molecular chains arrangement of the block copolymers were characterized by Fourier transform infrared (FTIR) spectroscopy, solid-state ¹³C-NMR and wide angle X-ray diffraction (WAXD). Thermal stability of the copolymers was investigated by thermogravimetric analysis (TGA) in nitrogen. Thin films of PBO and copolymers were cast from methanesulfonic acid (MSA) solutions. Both the films and fibers were exposed to UV light to determine their photostability. Changes in the chemical structures and surface morphologies of the films were characterized by FTIR spectra and scanning electronic microscopy (SEM), respectively. After UV light exposure, the retention of strength for copolymer fibers is improved compared to PBO fibers. The results revealed that copolymers suffered less photodegradation in comparison with homopolymer. The mechanism for the improved photostability of the copolymers was discussed.     

Unexpected formation of a xanthone in the synthesis of a bisbenzoxazole

Recently we reported the synthesis in polyphosphoric acid of a graft copolymer consisting of a rigid-rod poly[benzo(1,2-d;4,5-d′)bisthiazole-2,6-diyl]-1,4-phenylene backbone and flexible poly(oxy-1,3-phenylenecarbonyl-1,4-phenylene) side-chains [1]. However, upon extension of this synthetic approach to the analogous graft copolymer with a poly[benzo(1,2-d:5,4-d′)bisoxazole-2,6-diyl]-1,4-phenylene backbone, we encountered some unexpected results due to methyl group migration. In order to better understand these results, we carried out the synthesis of selected benzothiazole and benzoxazole structures under appropriate reaction conditions. The results are reported in this article.     

Studies on dilute solutions of rodlike macroions. II. Electrostatic effects

A group of rodlike polymers soluble only in strong protic acids was studied using light scattering and viscosity techniques. These include poly(1,4-phenylene benzobisoxazole), poly(1,4-phenylene benzobisthiazole) and poly(1,4-phenylene terephthalamide). The solution properties were dependent on the ionic strength of the acid used as solvent. In a low ionic strength acid such as chlorosulfonic acid, the polymer solutions exhibited decreased unpolarized scattering, an extremely small translational diffusion coefficient, and high viscosity. All of these effects could be eliminated by the addition of a salt such as lithium chlorosulfonate, which increased the ionic strength of the solvent. The effects were attributed to a pseudo ordering of the polymer solvent system caused by electrostatic repulsions between protonated polymer chains effective over large distances (ca. 100 Å) in the low ionic strength solvent. This type of ordering is distinct from actual anisotropic phase formation, which occurs at higher concentrations in these systems. Analysis of data at infinite dilution gave a persistence length of at least 45 nm for poly(1,4-phenylene terephthalamide), larger than previous experimental results, but in accord with recent rotational isomeric state calculations and similar to experimental data for poly(p-benzamide).     

Synthesis and Thermal Behavior of Polyesters Derived from 1,3‐Propanediol and Various Aromatic Dicarboxylic Acids

Abstract

Seven aromatic dicarboxylic acids were esterified by melt polycondensation in two steps with 1,3‐propanediol (1,3‐PDO) in the presence of tetrabutoxytitanium as catalyst. The acids used were: terephthalic (TPA), isophthalic (IPA), naphthalene‐2,6‐dicarboxylic (2,6‐NDA), naphthalene‐1,4‐dicarboxylic (1,4‐NDA), biphenyl‐4,4^′‐dicarboxylic (4,4^′‐BPDA), diphenylsulfone‐4,4^′‐dicarboxylic (4,4^′‐DPSDA), and pyridine‐2,6‐dicarboxylic acid (2,6‐PDA). In the first step, the esterification reaction was monitored, by measuring the distilled water. The prepared oligomers were polycondensated in a second step under high vacuum using the same catalyst as before. The received poly(propylene dicarboxylate)s were characterized by viscometry, carboxyl end‐group content (CC), color measurement, and were studied by differential scanning calorimetry (DSC). From this study, the above polyesters could be classified to three classes: (a) easily crystallizing polyesters derived from TPA and 2,6‐PDA, (b) slow crystallizing polyesters derived from IPA and 2,6‐NDA, and (c) amorphous polyesters derived from 1,4‐NDA, 4,4^′‐BPDA, and 4,4^′‐DPSDA.     

The synthesis,characterization, and crystal structures of poly(2,6‐naphthalenebenzobisoxazole) and poly(1,5‐naphthalenebenzobisoxazole)

The rigid‐rod polymers, poly(2,6‐naphthalenebenzobisoxazole) (Naph‐2,6‐PBO) and poly(1,5‐naphthalenebenzobisoxazole) (Naph‐1,5‐PBO) were synthesized by high temperature polycondensation of isomeric naphthalene dicarboxylic acids with 4,6‐diaminoresorcinol dihydrochloride in polyphosphoric acid. Expectedly, these polymers were found to have high thermal as well as thermooxidative stabilities, similar to what has been reported for other polymers of this class. The chain conformations of Naph‐2,6‐PBO and Naph‐1,5‐PBO were trans and the crystal structures of Naph‐2,6‐PBO and Naph‐1,5‐PBO had the three‐dimensional order, although the axial disorder existed for both Naph‐2,6‐PBO and Naph‐1,5‐PBO. Naph‐2,6‐PBO exhibited a more pronounced axial disorder than Naph‐1,5‐PBO because of its more linear shape. The repeat unit distance for Naph‐2,6‐PBO (14.15 Å) was found to be larger compared with that of Naph‐1,5‐PBO (12.45 Å) because of the more kinked structure of the latter. The extents of staggering between the adjacent chains in the ac projection of the crystal structure were 0.25c and 0.23c for Naph‐2,6‐PBO and Naph‐1,5‐PBO, respectively. Naph‐1,5‐PBO has a more kinked and twisted chain structure relative to Naph‐2,6‐PBO. The kinked and twisted chain structure of Naph‐1,5‐PBO in the crystal seems to prevent slippage between adjacent chains in the crystal structure. The more perfect crystal structure of Naph‐1,5‐PBO may be due to this difficulty in the occurrence of the slippage. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1948–1957, 2006     

Hydroxydialkylamino cruciforms: amphoteric materials with unique photophysical properties

Two amphoteric cruciforms 6 and 7 (XF; 4,4'-[(1E,1'E)-(2,5-bis{[4-(dibutylamino)phenyl]ethynyl}-1,4-phenylene)bis(ethene-2,1-diyl)]diphenol, 4,4'-[{2,5-bis[(E)-4-(dibutylamino)styryl]-1,4-phenylene}bis(ethyne-2,1-diyl)]diphenol) were prepared by a Horner reaction followed by a Sonogashira coupling and subsequent deprotection. The XFs display significant changes in absorption and emission when exposed to trifluoroacetic acid, tetrabutylammonium hydroxide, and metal triflates. The substitution pattern of 6 and 7 leads to spatial separation of the frontier molecular orbitals, which allows the HOMO or LUMO of the XF to be addressed independently by acidic or basic agents. XF 6, which has hydroxyl groups on the styryl axis, displays changes in emission color upon exposure to ten amines in eight different solvents. The change in fluorescence upon the addition of amines was analyzed by linear discriminant analysis. These XFs may have potential in sensor applications for metal cations and amines.     

Novel conjugated polymer poly(benzobisoxazole-2,6-diylvinylene): synthesis and evidence of aggregate formation in methanesulfonic acid

A new conjugated polymer poly(benzobisoxazole-2,6-diylvinylene) (PBOV) has been synthesized as an analogue of poly(p-phenylene benzobisoxazole) (PBO). The comparison between PBOV and PBO has been carried out by Fourier transform infrared spectroscopy, thermogravimetric analysis, UV, and photoluminescence (PL) spectroscopy. The UV absorption peaks, PL excitation and emission wavelengths of PBOV have a significant red-shift due to the better electronic delocalization. Similar to PBO, it can be observed in the PL spectra of PBOV at various concentrations in methanesulfonic acid (MSA) that the intensity of emission was depressed and the highly structured emission spectra gradually changed to featureless, red-shifted, and broad spectra with increasing concentration. The change in emission spectra can be attributed to the existence of the interchain aggregates, although PBOV does not show highly ordered structure as PBO does.