含氟聚酰胺酸亚胺化反应动力学

利用动态热重法研究了两种含氟聚酰胺酸薄膜在连续升温过程中的亚胺化反应动力学.采用积分法确定了两种含氟聚酰胺酸的亚胺化反应动力学函数是g(α)=(1-α)-1-1(其中:α为转化率);分别由Ozawa、KAS和迭代法来求取反应的活化能Ea值.结果表明:由KAS法或迭代法求得的活化能比较可靠.在此基础上得出相关的动力学参数、动力学模型方程和动力学补偿效应表达式,为聚酰亚胺工艺参数的选择和工艺窗口的优化提供了理论依据.     

原位红外光谱法研究电纺聚酰胺酸纳米纤维膜热亚胺化过程

以均苯二酐和二苯醚二胺为原料合成聚酰胺酸溶液,通过静电纺丝法制得聚酰胺酸纳米纤维膜.利用原位红外技术研究亚胺化进程,并以优化的条件制得聚酰亚胺纳米纤维膜.研究结果表明,当升温速率为2℃/min时,在350℃可实现100%亚胺化;升温速率过快,纳米纤维膜的亚胺化程度较低;采用快速-慢速相结合的升温方法,则可以有效地提高亚胺化效率.     

热亚胺化过程中气氛和拉力对BPDA-PDA聚酰亚胺纤维结构与性能的影响

研究了3,3',4,4'-联苯四酸二酐-对苯二胺(BPDA-PDA)型聚酰胺酸(PAA)纤维热亚胺化过程中气氛和拉力对聚酰亚胺(PI)纤维结构和性能的影响. 热处理过程中, 恒温处理5 min时, 虽然不同气氛下纤维的表面形貌并无明显差异, 但N₂气下所得纤维的力学性能明显优于空气下的样品, N₂气保护作用下, 最高断裂强度和初始模量分别达到1.25和65.0 GPa. 恒温处理40 min时, N₂气对纤维表面形貌有明显的保护作用. 但对于力学性能, 气氛的影响仅在450 ℃时表现得非常明显. 低于450 ℃时, 长时间的热处理成为影响纤维力学性能的主要因素, 气氛的影响变得不明显. 高于450 ℃时, 在N₂气和空气中的纤维皆发生明显的降解, 从而严重影响其力学性能. 热亚胺化过程中施加的拉力会促进纤维热酰亚胺化过程中的膨胀. 随着拉力的增加PI纤维长度增加, 同时直径减小. PI纤维轴上(004)晶面的间距、 晶粒尺寸、 线性热膨胀系数(为负值)的绝对值及玻璃化转变温度都随热处理时拉力的增加而增大. 纤维的断裂强度随拉力的变化基本保持在0.90 GPa左右, 断裂伸长率随着拉力增加稍有下降, 纤维的初始模量随拉力的增大而增加.     

矿物药金礞石的红外光谱分析

采用傅立叶红外光谱法分析了金礞石试样,对所得图谱进行解析,发现试样的红外光谱具备层状硅酸盐矿物的吸收特征.其吸收带主要分为4个区域:3 700～3 000 cm-1区间的OH伸缩振动吸收,1 620 cm-1左右处的H2O弯曲振动吸收,1 000 cm-1左右处的Si-O伸缩振动吸收和550～400 cm-1区间的Si...     

顺丁烯二酸酐封端的新颖聚酰亚胺的合成及其结构性能研究Ⅰ．酰胺酸的合成及亚胺化动力学研究

报道合顺丁烯二酸酐基团的二苯甲酮四羧酸二酐双对氨基二苯醚酰胺酸（ＭＰＷ）的合成．该产物可用来制备具有优良性能的新颖聚酰亚胺。产物结构通过红外光谱、元素分析等进行表征。本文建立了用单谱ＤＳＣ法研究酰胺酸亚胺化动力学的新方法。结果表明其亚胺化反应级数ｎ＝３，在亚胺化过程中反应活化能及频率因子不随亚胺化程度增加而变化，数值亦保持不变。     

酚醛树脂固化过程的红外光谱分析

利用红外光谱(IR)及其变温样品池、定量分析程序对酚醛树脂固化过程中的结构变化进行了研究,它对于酚醛树脂固化过程的质量控制具有重要意义。     

二茂铁亚胺及其环汞化合物的薄层色谱及紫外-可见、红外光谱特征

通过测定R^f值对比研究了二茂铁亚胺及其环汞化合物的色谱亲和性,发现环汞化合物比未汞化的二茂铁亚胺具有较高的R_f值,并用N→Hg分子内配位作用给予解释。分析取代基效应表明,亚胺氮上电子密度越高,R_f值越小。紫外可见光谱表明,环汞化合物分子中存在有N→Hg分子内配位作用。研究了N-Ar环和亚胺碳上的取代基效应对紫外光谱的影响,与N-Ar环上无取代基时相比,π→π^*CT跃迁带的最大吸收波长移动值△λ_max和Hammett-Brown常数σ⁺之间存在良好的线性关系。考察了二茂铁红外光谱规则对所研究体系的适用情况。     

1—羟基蒽醌及其稀土络合物的红外光谱分析

制备了稀土离子Ｌｎ＾３＋（Ｌｎ＝Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｓｍ，Ｅｕ，Ｇｄ，Ｔｂ，Ｄｙ）与１－羟基蒽醌的络合物，测定了它们和氘代１－羟基蒽醌在４０００￣５０ｃｍ＾－１范围内的红外光谱，对观察红外吸收带进行分析和归属。发现了某些对金属离子敏感的谱带，确定了配位键的伸缩振动。     

聚酰胺酸贮存稳定性

在不同溶剂中合成了一系列均苯二酐（PMDA）、联苯四酸二酐（BPDA）、二苯硫醚二酐（TDPA）、三苯二醚二酐（HQDPA）型和二苯醚二酐（ODPA）型聚酰胺酸（PAA）,由PMDA和二氨基二苯甲烷（MDA）或3,3′－二甲基－4,4′－二氨基二苯甲烷（DMMDA）在N－甲基吡咯烷酮（NMP）中合成的PAA在室温下呈凝胶态,而其它PAA在室温下均为透明溶液,考察了贮存湿温度、凝胶态、添加分子筛等条件对PAA贮存稳定性的影响,发现PAA凝胶的贮存稳定性优于PAA溶液,在PAA溶液中加入4A分子筛时,有利于其它贮存期的延长。     

苯胺链段为侧基的聚酰胺酸的合成及性质

采用三元共聚法制备了苯胺齐聚物为侧链的接枝型聚酰胺酸. 通过红外光谱、核磁共振谱及高效凝胶渗透色谱等技术对聚合物结构进行了表征. 该材料亚胺化后具有十分优异的热稳定性. 紫外-可见光谱和电化学测试结果表明, 该聚合物具有独特的光谱性质和可逆的电化学活性. 聚酰胺酸/ITO电致变色电极具有颜色变化明显, 响应速度较快, 着色效率高等优点, 是一种综合性能较好的电致变色聚合物材料.     

Phase Behaviour of Poly(styrene-co-methacrylic acid)/ Poly(styrene-co-N,N-dimethylacrylamide)/Poly(styrene-co-4-vinylpyridine) Ternary Blends by DSC and FTIR

Summary: we have investigated by DSC and FTIR the miscibility and phase behaviour of binary and ternary blends of different ratios of poly(styrene-co-methacrylic acid) containing 15 mol% of methacrylic acid (SMA15) with poly(styrene-co-N,N-dimethylacrylamide) containing 17 mol% of N,N,-dimethylacrylamide (SAD-17) and poly(styrene- co-4-vinylpyridine) containing 15 mol% of 4-vinylpyridine. SMA15 is miscible with both SAD17 and S4VP15 and interacts more strongly with S4VP15 than with SAD17 as evidenced by the positive deviations from linear average line observed with these blends and the appearance of new bands in the 1800–1550 cm⁻¹ region. This behaviour is known as ΔK effect. The FTIR study confirms that though the specific intermolecular interactions that occurred with each pair of the SMA15/S4VP15 and SMA15/SAD17 binary components are of different strength, they still exist in the ternary blend. Even though the three binary polymer pairs are individually miscible, the ternary system of SMA15/S4VP15/SAD17 exhibits only partial miscibility with small loop of immiscibility due to a significant ΔK effect. These results obtained by DSC and FTIR are in a fair agreement with theoretical prediction applying the Painter-Coleman association model.     

硫醚双酐聚酰胺酸的合成及其热稳定性

合成了硫醚二酐和4-硝基-4'-[N,N-二(2-氨乙基)氨基]偶氮苯(二胺单体)及对应的硫醚聚酰胺酸,并对其结构进行表征.由于该发色团分子的一端有可以进一步聚合的氨基,它与硫醚酐所形成的聚酰胺酸在普通有机溶剂中具有良好的可溶性,NLO发色团和聚酰亚胺骨架的分解温度t_d分别为362℃和491℃,显现出了特殊的热稳定性.目前,这些聚合物在高敏感非线性光学材料方面显示着广泛的应用前景.     

采用流变学方法研究聚酰胺酸6FDA-TFDB溶液的降解行为

合成了一种聚酰胺酸6FDA-TFDB溶液,利用流变仪研究其在不同影响因素(如:温度、升温速率、溶剂含水量等)下的流变行为,发现聚酰胺酸溶液的降解在高温区和低温区存在不同的行为.通过Andrade公式获得不同条件下聚酰胺酸溶液的黏流活化能,并比较其差异,同时对溶剂水含量在不同温度区域下对聚酰胺酸降解速率的影响也进行了深入的分析,从而建立一种半定量比较不同条件下聚酰胺酸溶液降解速率的方法.     

Simple and easy recycling of poly(amic acid) gels through microwave irradiation

Poly(amic acid)s (PAAs), which are precursors of polyimides, often undergo gel formation during their synthesis or storage, and these insoluble gels have been discarded. In this work, we discovered that the gels could be converted to homogeneous PAA solutions by fast and simple microwave (MW) irradiation. The PAA gels were placed inside a domestic MW oven, and MW irradiation was carried out with 240 W for 2 min. The recycled PAA solutions afforded polyimide films, coatings, and powders. The polyimides prepared from the recycled PAA solutions exhibited higher glass transition temperatures (T_gs), decomposition temperatures, and char yields than comparison polyimides obtained from ordinary PAA solutions. Flexible free‐standing polyimide films were obtained by drop‐casting of the MW‐treated solutions and subsequent thermal imidization. Mechanical properties and dielectric constants were measured for the polyimide films and coatings, respectively. This new method has significant advantages for the environment, economy, and industry. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 981–987     

Poly(amic acid) salt‐mediated palladium and platinum nanoparticles as highly active and recyclable catalysts for hydrogenation of nitroarenes in water under ambient conditions

Development of highly active and recyclable catalysts for selective hydrogenation of nitroarenes to amines in water at room temperature is always a challenge in chemical industry. This study reports a facile in situ method for synthesis of ultrafine palladium and platinum nanoparticles (NPs) stabilized by poly (amic acid) salt (PAAS) and their potential as catalysts for hydrogenation of nitroarenes with sodium borohydride or molecular hydrogen as reductant in water at room temperature. In the reduction of 4‐nitrophenol to 4‐aminophenol by sodium borohydride, the activity parameters of PdNPs–PAAS and PtNPs–PAAS catalyst is 6.66 × 10³ and 5.58 × 10³ s^?1 M^?1 respectively. In the hydrogenation of diverse nitroarenes under atmospheric hydrogen pressure, PdNPs–PAAS shows high activity but poor selectivity toward desired amines in some cases, while PtNPs–PAAS shows both high activity and high selectivity for selective hydrogenation of nitroarenes to corresponding anilines. The high efficiency of nanocatalyst is due to the quasi‐homogeneous dispersion of metal NPs and synergistic effects between metal NPs and PAAS. In addition, nanocatalyst can be easily recovered with pH‐sensibility of PAAS and reused at least six times without significant loss of catalytic activities.