光敏聚合物薄膜光化学性能及其诱导液晶分子取向性能的研究

本文采用动态紫外光谱法测试了含有香豆素光敏基团的聚合物薄膜的光化学性能,考察了不同曝光温度和曝光能量条件下的光敏聚合物的光化学性能,以及不同热处理条件下聚合物薄膜诱导液晶分子取向性能。研究结果表明:在曝光温度为130℃时,聚合物薄膜在最小曝光量下发生光化学反应后产生的光学各向异性ΔA达到最大,并且对应光反应程度DP在45%左右;当曝光能量为320mJ/cm~2和384mJ/cm~2、对应热处理温度为160℃时,聚合物薄膜诱导液晶分子取向所产生的各向异性ΔA和有序度参数S达到最大,分别为0.22和0.048。     

肉桂酸酯系光敏聚合物的光致诱蚀作用机理研究

光致诱蚀作用或无显影气相光刻作用是一个非常有趣的现象。为了探讨肉桂酸酯系光敏聚合物的光致诱蚀作用机理,观察了各种因素的相互影响。提出了下述理论假设:当肉桂酸酯光敏聚合物薄膜受紫外光照射时,发生光化学反应并使其结构性质发生变化,从而使得薄膜可以从腐蚀气体中吸收H_2O和HF气体,形成一个氢氟酸-聚合物溶液,此溶液与HF和H_2O的混和气体不同,可以与其下部的SiO_2迅速反应。但未受光照射的区域不易同时吸收H_2O和HF,其下部SiO_2的反应速度很慢,于是在两个区域间形成了很大的腐蚀速度差,从而形成一个清晰的光刻图象。这个假设可以解释现有的全部实验结果。     

离子色谱法测定大气PM2.5中高氯酸盐的含量

正高氯酸盐是一种具有高氧化性和高稳定性的非挥发可溶盐,主要以气溶胶的形式存在于大气中,是新型且持久的环境微量无机污染物~([1-4])。已有研究表明高氯酸盐可对甲状腺功能、机体代谢以及发育产生干扰,主要机理表现为阻碍人体甲状腺对I-的吸收,对孕妇以及婴幼儿的影响尤为显著,严重时也可诱发甲状腺癌~([5-6])。大气中的高氯酸盐主要来源分为自然源和人为源,自然源是通过臭氧氧化、光化学反应、闪电作用等大气化学反应生成~([3]),     

煤改性聚乙烯塑料的降解性能及其机理探讨

通过对力学性能、红外光谱、粘均分子量及扫描电镜的分析,研究了煤/聚乙烯塑料在室内加速老化实验中的降解性能,并运用降解机理对实验过程进行解析及验证。结果表明,煤降解剂引发的交联和降解反应控制了薄膜的强度,使其柔韧性一直降低,且在整个120h光照过程中,断裂伸长率一直呈下降趋势;72h前是聚合物的氧化诱导期及衰变期,之后进入完全降解期。煤在改性塑料光照过程中引发自由基反应,引入羰基,导致聚乙烯大分子断链降解;共聚物的粘均分子量整体呈降低趋势,说明光照促进聚合物的降解,降解和交联交替控制着反应。煤/聚乙烯的光降解过程遵循链引发、链增长、链终止反应机理,在煤大分子光催化作用下,改变了聚乙烯常规光降解过程,加速了聚乙烯大分子断链和分子量降低。运用煤/聚乙烯塑料降解机理,能够解释样品力学性能变化、化学结构中羰基指数变化、分子量降低及降解过程中的现象和规律。     

茂金属聚乙烯的短链支化结构不均匀性研究进展

茂金属支化聚乙烯技术是聚烯烃工业发展史上最重要的技术进展之一,该类产品具有优异的抗穿刺、抗撕裂、抗冲击性质,在薄膜、重包装等领域具有广泛的用途,其力学性能与共聚单体的种类、含量及其在分子链上的分布有密切关系。本文从催化剂活性中心特点和聚合反应工艺条件两方面对聚合物结构的影响出发,阐述了茂金属聚乙烯短链支化结构不均匀性产生的原因,通过核磁共振、升温淋洗分级和热分级等表征支化不均匀性的研究方法,介绍了茂金属支化聚乙烯分子主链上共聚单体的序列结构组成及分布,以及共聚物的结晶性能等方面的差异。     

微反应器控制的化学反应的选择性

研究利用分子筛、Nafion薄膜、低密度聚乙烯薄膜和囊泡作为微反应器控制有机光化学反应的方向,提高反应的选择性和可能性.在NaY沸石或低密度聚乙烯薄膜中,带有长烷基链或醚链的二芳基化合物光二聚只生成分子内的加成产物,而不生成分子间的加成产物,从而在底物浓度很大的情况下,高选择性地合成了大环化合物.通过控制底物和敏化剂分子在ZSM-5沸石、Nafion薄膜和囊泡中的分布高选择性地控制烯烃光敏氧化反应的方向,单一地生成单重态氧的氧化产物或超氧负离子的氧化产物.利用Nafion薄膜作为介质进行光诱导电子转移,得到超长寿命的电荷分离态.     

HDPE/LDPE共混物形变过程中的结构变化及机理

聚合物熔体结晶由于链缠结等因素的影响,其形态结构非常复杂,这给研究结晶聚合物的微观结构,特别是聚合物在拉伸过程中的形态变化带来很大困难．本文将高密度聚乙烯（ＨＤＰＥ）和低密度聚乙烯（ＬＤＰＥ）两种不相容的组分进行共混,使少量ＨＤＰＥ分散在ＬＤＰＥ中,...     

石英晶体微天平在聚合物薄膜研究中的应用与展望

石英晶体微天平仪(QCM)具有高度的灵敏性,能够对石英晶片表面微痕量物质的变化产生响应,在分析科学研究中广泛应用.本文阐述了QCM的基本工作原理和应用基础方程,并在此基础上综述了近年来QCM在聚合物薄膜研究中的应用及研究进展,包括QCM对聚合物薄膜的厚度和力学性能的测量、QCM研究聚合物分子链在石英晶片表面的吸附过程和链构象变化、表面引发生长聚合物刷的动力学过程、基于功能聚合物薄膜和QCM的生物与化学传感器等,同时对QCM在聚合物薄膜研究领域的进一步深入应用进行了展望.     

聚乙烯胺对钙钛矿薄膜相态结构的有效调控

将聚乙烯胺的碘酸盐PVAm·HI引入钙钛矿的前驱体溶液,部分代替MAI的作用,通过聚合物PVAm·HI的铵离子占据钙钛矿表面的A位置,利用聚合物PVAm·HI主链骨架的共价键将钙钛矿晶粒连接起来,达到有效控制钙钛矿相态结构的目的。通过1 H-NMR、SEM、XRD等表征了聚合物PVAm·HI氨离子对钙钛矿表面A位置的有效占据。通过薄膜光伏性能的表征可知:聚合物PVAm·HI的引入不但使得钙钛矿薄膜中针孔消失、晶粒尺寸减小、薄膜的致密性增加,同时也提高了钙钛矿太阳能电池的长期稳定性。     

电致变色/电控荧光双功能聚合物的合成及性能

将电活性双胺单体4,4'-二氨基二苯醚与1,2,4,5-环己烷四甲酸二酐共聚, 得到电活性聚酰胺酸聚合物. 再通过后功能化方法, 采用酰胺化反应将2-氨基芴引入到聚合物结构中, 合成了荧光聚合物. 通过核磁、 红外和凝胶渗透色谱证实了聚合物的结构. 该聚合物在0~0.8 V的电压下展示出可逆的电化学活性. 在利用电压改变苯胺齐聚物链段的氧化状态的过程中, 聚合物薄膜发生了明显的颜色变化, 展现出良好的电致变色性质. 荧光性质随着施加电压的改变而变化, 展现出优异的电控荧光特性.     

聚乙烯薄膜中微量羰基的紫外分析法——薄膜中苯腙的生成及其影响因素

<正> 将分析有机物中2,4-二硝基苯脘的紫外光谱法(简称DNPH-UV法)用于固体高分子材料的羰基检测,在70年代才有报道.Kato利用DNPH-UV法和红外光谱法(IR法)跟踪聚乙烯薄膜在光氧化中羰基的生成数据,两者的检测灵敏度几乎相同,而Johnson等用前一方法曾检出聚乙烯薄膜中有极少量羰基存在,但缺少相应的IR数据,其灵敏度难以判断.此外,在应用DNPH-UV法时,所规定的反应条件也不同,对影响反应的各种因素,特别是对检测灵敏度的影响,仍缺乏资料.因此本文以聚乙烯薄膜为对象,对样品的氧化程度、厚度及其反应条件和反应液的组分等进行了研究.     

一种新型老化评价系统及在聚乙烯复合材料中的应用

建立了一种高灵敏度、多环境因素耦合的新型老化评价系统,可以实现在光、热、氧、湿等多种环境因素条件的耦合下,对高分子材料快速、灵敏、实时、无损的老化评价.该系统被用于聚乙烯(PE)复合材料的稳定性和老化状态的评价以及PE老化动力学的研究.结果表明,该系统测定的CO2生成速率与PE复合材料自然老化下的氧化程度具有良好的对应性,同时能够精确反映PE复合材料的自然老化状态—不同自然老化时间的PE复合材料,其CO2生成速率与羰基指数的对数呈线性关系.此外,该系统还可以快速、准确地测定PE老化过程的活化能.     

HDPE,LLDPE或LDPE高取向薄膜微结构的电子显微学研究

木工作用透射电子显微术及电子衍射技术研究3种PE(HDPE,LLDPE或LDPE)均聚物高取向薄膜的微结构。定量测定了它们的结晶尺寸。通过倾斜样品电子显微学研究确定了不同种PE纤维结构的对称性。     

Quasi-equilibrium volume changes of polyaniline films upon redox switching. Formal potential distribution and configurational modeling

The quasi-equilibrium electrochemomechanical behavior of relatively thick polyaniline films in sulfuric acid is investigated through experimental measurements and theoretical modeling. The leucoemeraldine (LE)-emeraldine (EM) conversion, or redox switching, is studied. The dependence of film volume and electrochemical charge is determined as a function of applied potential. It is observed that the film volume follows the charge, showing an expansion during the second half of the LE-EM oxidation. The model postulates the existence of a stable intermediate, protoemeraldine (PE), with a formal potential distribution for the PE-EM reaction. The volume change is modeled statistically considering contributions from mixing, polymer deformation, and electrostatic charge. The model shows very good agreement with the experiments, indicating that, in the conditions studied, the deformation contribution dominates the volume changes as a result of the conformational modifications undergone by the polymer in the PE-EM oxidation.     

Effect of extrusion and photo-oxidation on polyethylene/clay nanocomposites

Polyethylene (a 1:1 blend of m-LLDPE and z-LLDPE) double layer silicate clay nanocomposites were prepared by melt extrusion using a twin screw extruder. Maleic anhydride grafted polyethylene (PEgMA) was used as a compatibiliser to enhance the dispersion of two organically modified monmorilonite clays (OMMT): Closite 15A (CL15) and nanofill SE 3000 (NF), and natural montmorillonite (NaMMT). The clay dispersion and morphology obtained in the extruded nanocomposite samples were fully characterised both after processing and during photo-oxidation by a number of complementary analytical techniques. The effects of the compatibiliser, the organoclay modifier (quartenary alkyl ammonium surfactant) and the clays on the behaviour of the nanocomposites during processing and under accelerated weathering conditions were investigated. X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), rheometry and attenuated reflectance spectroscopy (ATR-FTIR) showed that the nanocomposite structure obtained is dependent on the type of clay used, the presence or absence of a compatibiliser and the environment the samples are exposed to. The results revealed that during processing PE/clay nanocomposites are formed in the presence of the compatibiliser PEgMA giving a hybrid exfoliated and intercalated structures, while microcomposites were obtained in the absence of PEgMA; the unmodified NaMMT-containing samples showed encapsulated clay structures with limited extent of dispersion in the polymer matrix. The effect of processing on the thermal stability of the OMMT-containing polymer samples was determined by measuring the additional amount of vinyl-type unsaturation formed due to a Hoffman elimination reaction that takes place in the alkyl ammonium surfactant of the modified clay at elevated temperatures. The results indicate that OMMT is responsible for the higher levels of unsaturation found in OMMT-PE samples when compared to both the polymer control and the NaMMT-PE samples and confirms the instability of the alkyl ammonium surfactant during melt processing and its deleterious effects on the durability aspects of nanocomposite products. The photostability of the PE/clay nanocomposites under accelerated weathering conditions was monitored by following changes in their infrared signatures and mechanical properties. The rate of photo-oxidation of the compatibilised PE/PEgMA/OMMT nanocomposites was much higher than that of the PE/OMMT (in absence of PEgMA) counterparts, the polymer controls and the PE–NaMMT sample. Several factors have been observed that can explain the difference in the photo-oxidative stability of the PE/clay nanocomposites including the adverse role played by the thermal decomposition products of the alkyl ammonium surfactant, the photo-instability of PEgMA, unfavourable interactions between PEgMA and products formed in the polymer as a consequence of the degradation of the surfactant on the clay, as well as a contribution from a much higher extent of exfoliated structures, determined by TEM, formed with increasing UV-exposure times.     

MISCIBILITY AND MORPHOLOGY OF THIN FILMS OF BLENDS OF POLYSTYRENE WITH BROMINATED POLYSTYRENES： EFFECTS OF VARYING THE MOLECULAR WEIGHT, BROMINATION DEGREE AND ANNEALING

Thin films of incompatible polymer blends can form a variety of structures during preparation and subsequent annealing process. For the polymer blend system consisting of polystyrene and poIy(styrene-co-p-bromo-styrene), i.e., PS/PBrxS, its compatibility could be adjusted by varying the degree of bromination and the molecular weight of both components comprised, in this paper, surface chemical compositions of the cast and the annealing films were investigated by X-ray photoelectron spectroscopy (XPS) and contact angle measurement; meanwhile, surface topographical changes are followed by atomic force microscopy (AFM). In addition, substantial attention was paid to the effect of annealing on the morphologic variations induced by phase separation and/or dewetting of the thin film. Moreover, the influences of the molecular weight, Aw, as well as the brominated degree, x%, on the sample surface are explored systematically, and the corresponding observations are explained in virtue of the Flory-Huggins theory, along with the dewetting of the polymer thin film.     

差示扫描量热法测定聚乙烯结晶度的不确定度评定

采用差示扫描量热法(DSC)测定聚乙烯(PE)的结晶度，讨论了测定PE熔融焓过程中由测量重复性、称量过程及PE本身结构的不均匀性等因素所带来的不确定度分量，计算了测定PE熔融焓的合成标准不确定度及扩展不确定度和测定PE结晶度的扩展不确定度。采用Dsc法测定高密度聚乙烯(HDPE)和低密度聚乙烯(LDPE)结晶度的扩展不确定度均小于l％。     

N-苯基-双环[2.2.1]庚-5-烯-2,3-二甲酰亚胺的热聚合反应

以核磁共振波谱和溴加成法分析N-苯基-双环[2.2.1]庚-5-烯-2,3-二甲酰亚胺的聚合物的化学结构。聚合物分子具有含内、外式双环[2.2.1]庚-5-烯双键和环戊烯双键的结构单元。半定量地测定了各类双键的含量。分子的饱和链段有5,7-位相连的外式构型和5,6-位相连的内式构型的双环[2.2.1]庚烷的结构单元。结果表明,聚合过程中有构型的转变,重排反应,以及不同的链增长途径。     

聚酰亚胺LB膜热解制备SiC薄膜的XPS研究

用XPS对沉积在硅基片上的聚酰亚胺LB膜以及由它真空热解制备的SiC薄膜进行了研究 ,并对其形成过程进行了跟踪分析 .XPS结果显示聚酰亚胺LB膜结构均匀 ,质量良好 ;真空热解时 ,约在 6 70℃时LB膜中的C与衬底Si反应形成SiC ;Ar离子溅射深度俄歇谱表明所制备的SiC膜中Si和C浓度成梯度分布 ,说明SiC是由Si和C相互扩散反应形成的     

Formation and reaction of polyenesulfonic acid. I. Reaction of polyethylene films with SO3

The surface of polyethylene (PE) film was sulfonated by reaction with gaseous SO₃. The structure of the sulfonated PE films was determined on the basis of spectroscopic data such as IR, UV, and resonance Raman spectra. It was confirmed that a PE film and SO₃ gave unsaturated sulfonic acids and that, as the reaction proceeded, the elimination of sulfurous acids took place to form sulfonic acids having highly conjugated C?C unsaturated bonds.