液晶冠醚LB膜的制备及其性质研究

本文首次研究了五种新合成的液晶冠醚ＬＢ膜的成膜特性。实验发现，其中的单臂胆甾型液晶冠醚在气－液界面易形成稳定的单分子膜，但不易累积形成ＬＢ膜；芳香酯类的单臂液晶冠醚膜的稳定性与链的长短有关；而双臂芳香酯型二氮杂１８－冠－６易形成稳定的膜，且具有特殊的相变性质。膜的特性与物质的化学结构有关，借助ＣＰＫ分子模型，对成膜后分子构型进行了估算，理论计算与实验一致。对纯组分以及单臂液晶冠醚与硬脂酸的混合膜结构，用表面压－面积曲线以及小角Ｘ衍射等进行了表征，并对其中的双臂液晶冠醚作了离子识别功能研究。     

含液晶基团的冠醚LB膜研究

合成了含有联苯介晶基团的长链冠醚,并首次制成含液晶基团的冠醚LB膜,由LB膜的荧光光谱研究发现,与其单体在CHCl_3稀溶液中的荧光光谱相比,LB膜的荧光光谱向长波方向移动,表明分子均以缔结状态存在,XRD结果表明,LB膜具有良好的有序结构,单分子膜厚2.6nm。     

双臂胆甾醇酯型氮杂冠醚化合物的LB膜研究

研究了含有双臂胆甾基的氮杂冠醚化合物的单分子膜成膜特性,测试了其LB膜的吸收光谱和小角X-射线衍射谱。结果表明,这种化合物成膜性能和转移性能比单臂的胆甾基氮杂冠醚化合物好。结合CPK原子模型,推测了该分子在膜中的取向和构型。     

单臂脂环18-冠-6液晶的合成

本文合成了两种单臂脂环18-冠-6-液晶, 羟甲基 18-冠-6分别和4-(4'-正丁氧基苯甲酰氧基)苯甲酰氯或氯甲酸胆甾醇酯反应得到两种目标物,用DSC和偏光显微镜测定其相变温度,前者相变温度是T~K~N4.0℃和T~N~I33.5℃, 后者相变温度T~K~S-22.4℃, T~S~N6.8℃, T~N~I40.4℃, 用等克分子的硬脂酸和该冠醚液晶制成LB膜, 观察到Y型LB膜的特征.     

单臂液晶冠醚LB膜的研究

首次研究了４种单液晶冠醚（１～４）的ＬＢ膜成膜特性，实验发现它们在气－液界面均可形成单分子膜，但４的稳定性较差，３易转移到玻璃基片上形成Ｙ型膜。４种化合物与硬脂酸以１：１混合形成稳定的Ｙ型ＬＢ膜。小角Ｘ射线衍射证实了膜的有序结构。用ＣＰＫ原子模型对成膜分子构型和面积进行了估算，其结果与实验一致。并讨论了分子结构对成膜性能的影响。     

冠醚和卟啉与花生酸混合单分子膜行为研究

本文将3'-正十五烷基苯并15-冠-5和六种无脂链难于直接成膜的四苯基卟啉与花生酸混合形成单分子膜。结果表明, 冠醚被嵌进而卟啉被挤出花生酸单分子层。卟啉-花生镉LB膜的可见吸收光谱指出卟啉分子成团聚集。扫描电镜观察了卟啉-花生酸镉混合LB膜的表面形貌, 在膜表面上无金涂层时直接测到了混合膜的相分离。     

液晶冠醚、碳纳米管、水溶性杯芳烃在分析化学中的应用

综述了液晶冠醚、碳纳米管、水溶性杯芳烃在分析化学中应用的新进展。介绍了液晶冠醚在离子传输、分子识别、色谱分析、LB膜等各方面的应用;讨论了碳纳米管在扫描显微镜探针针尖、气体传感器、化学修饰电极和化学分离与检测方面的应用,以及水溶性杯芳烃在光度法、电化学、色谱分离方面的应用。     

新型两亲性酞菁锌LB膜的研究

本文合成了一种新型的两亲性酞菁分子,研究了它在不同溶剂中的聚集行为,考察了酞菁及酞菁与正十六烷混合的成膜性能,制备了混合的多层LB膜,并利用紫外光谱研究LB膜内的分子聚集状况,用分子激子理论对实验结果加以分析,还应用偏振紫外的方法对LB膜内酞菁分子大环的取向进行了确定。     

一种新的具有给体-受体结构的有机分子的合成及LB膜研究

本工作合成了一种新的具有给体-受体结构的长碳链有机分子, 2, 3-二(十六烷硫基)-5-(4'-硝基苯亚甲基)-1, 4-二硫代-2-环戊烯, 对其单分子膜的成膜性能进行了研究。在适宜条件下制备了单层及多层LB膜。通过电子衍射、X射线衍射、紫外-可见吸收光谱等手段对LB膜的结构进行了表征。实验结果表明, 这种化合物的成膜性能很好。单分子层膜的二次谐波测试表明该发色团分子具有较好的二阶非线性光学性。     

胆甾液晶二氮杂冠醚-Eu(Ⅲ)配合物LB膜和荧光性质研究

研究了胆甾液晶二氮杂冠醚N,N'-双[胆甾-5-烯-3β-氧羰甲基]-1,10-二氮-4,7,13,16-四氧环十八烷(1)及其与Eu³⁺的配合物(2)、2与苯甲酸的混配物(3)的LB膜和荧光性质.结果表明:1、2和3都在水溶液亚相液面形成稳定的单分子膜,但只有1的单分子面积受亚相pH的影响.1、2和3的单分子膜都容易转移到石英基片上形成LB膜,其中2和3为X型,转移比分别为0.6和1.0.在LB膜中,在2的荧光激发波长范围比在溶液中的宽,荧光强度也比在溶液中的强得多.在2中添加苯甲酸形成3可改善LB膜中分子有序排列,荧光强度增强到无苯甲酸时的2.0倍.所有这些LB膜,即使添加了苯甲酸的,都不是很稳定.     

液晶研究（Ⅰ）──4＇－酰基－4－羟基－1，1＇－联苯酯类液晶的合成与性质

以４＇－羟基联苯为原料合成了８种新型４＇－酰基－４－羟基联苯酯类化合物．除化合物５＿ｈ外，均为新的近晶相液晶化合物．它们具有较宽的相变温度范围和较高的热稳定性．用偏光显微镜和差热分析仪研究了它们的相行为，讨论了分子结构对液晶相行为的影响．     

大分子拥挤环境中脂肪酸影响磷脂囊泡相变的差示扫描量热研究

脂肪酸诱导的磷脂膜的热力学行为对于认识细胞内复杂的机制有着重要意义,而前人在研究脂肪酸与磷脂膜相互作用时大都在稀溶液中进行;拥挤环境下脂肪酸诱导磷脂膜的相变行为还未见报道。本文以二肉豆蔻酰磷脂酰胆碱(DMPC)构建囊泡模型,采用差示扫描量热法系统地研究了在不同浓度、不同分子量的聚乙二醇(PEG)拥挤环境中不同结构的脂肪酸对DMPC磷脂囊泡相变的影响。研究结果表明,在拥挤环境中,PEG对纯的磷脂囊泡相变的影响与大分子的分子量和浓度相关。对于脂肪酸/磷脂囊泡(FA/DMPC),PEG的存在对囊泡相变产生显著影响。在所考察的分子量和浓度范围内,PEG使FA/DMPC囊泡相变增加。短链饱和脂肪酸、不饱和脂肪酸原本使DPMC囊泡相变降低,但PEG缩小了降低幅度,甚至导致相变增加。进一步的研究表明,在大多数情况下,PEG对FA/DMPC的相变具有协作增强效应,且其影响均与大分子的分子量和浓度相关。另外,随着PEG浓度的升高,磷脂囊泡的协同单位数逐渐降低,表明拥挤环境会影响磷脂双分子层的均一性,使协同发生相变的分子数降低。本文的研究表明,大分子拥挤环境能够对扰动的磷脂双分子层起到一定的修复作用,这一现象在生物膜相关领域不可忽视。     

Detailed Investigation of the Structural,Thermal, and Electronic Properties of Gold Isocyanide Complexes with Mechano‐Triggered Single‐Crystal‐to‐Single‐Crystal Phase Transitions

Mechano‐induced phase transitions in organic crystalline materials, which can alter their properties, have received much attention. However, most mechano‐responsive molecular crystals exhibit crystal‐to‐amorphous phase transitions, and the intermolecular interaction patterns in the daughter phase are difficult to characterize. We have investigated phenyl(phenylisocyanide)gold(I) ( 1 ) and phenyl(3,5‐dimethylphenylisocyanide)gold(I) ( 2 ) complexes, which exhibit a mechano‐triggered single‐crystal‐to‐single‐crystal phase transition. Previous reports of complexes 1 and 2 have focused on the relationships between the crystalline structures and photoluminescence properties; in this work we have focused on other aspects. The face index measurements of complexes 1 and 2 before and after the mechano‐induced phase transitions have indicated that they undergo non‐epitaxial phase transitions without a rigorous orientational relationship between the mother and daughter phases. Differential scanning calorimetry analyses revealed the phase transition of complex 1 to be enthalpically driven by the formation of new aurophilic interactions. In contrast, the phase transition of complex 2 was found to be entropically driven, with the closure of an empty void in the mother phase. Scanning electron microscopy observation showed that the degree of the charging effect of both complexes 1 and 2 was changed by the phase transitions, which suggests that the formation of the aurophilic interactions affords more effective conductive pathways. Moreover, flash‐photolysis time‐resolved microwave conductivity measurements revealed that complex 1 increased in conductivity after the phase change, whereas the conductivity of complex 2 decreased. These contrasting results were explained by the different patterns in the aurophilic interactions. Finally, an intriguing disappearing polymorphism of complex 2 has been reported, in which a polymorph form could not be obtained again after some period of time, even with repeated trials. The present studies provide us with a variety of hitherto unknown insights into mechano‐responsive molecular crystals, which help us to understand the phase transition behaviors upon mechanical stimulation and establish rational design principles.     

具有可控温敏相变行为的四氢呋喃-缩水甘油超支化共聚醚的合成

采用四氢呋喃(THF)和缩水甘油(glycidol)进行阳离子开环共聚,一步合成了主链中含有柔性聚四氢呋喃线型链段的温敏性超支化共聚醚.采用定量13C-NMR确定了共聚醚的超支化结构,同时计算了其支化度.利用体积排除色谱-多角度激光光散射(SEC-MALLS)对聚合物分子量及分布进行了表征.紫外-可见光光谱(UV)测试发现共聚醚水溶液透过率在最低临界溶解温度(LCST)附近呈现剧烈变化,但是其相变速率缓慢,相变平衡时间可达30 min;且聚合物溶液的相变速率和紫外光透过率变化具有温度依赖性.采用透射电镜(TEM)对相变过程观察后发现,这种缓慢相变过程是由于超支化共聚醚组装形成的胶束随温度升高发生不同程度聚集所致.     

Thickness-dependent phase transition of AlxGa1-xN thin films on strained GaN

We report our investigation of phase transition of AlxGa1-xN thin films on GaN made by employing first-principles calculations. A critical thickness of two AlGaN molecular layers is determined for the wurtzite-to-zinc blende structural transition under compressive strains, which is associated with the second-nearest-neighbor interaction of electron bonds. Higher AlN mole fractions are found to favor the phase transition because of strong push toward covalency of the Al-N bonds under strains. Electronic structure results show that, after the phase transition, the spontaneous and piezoelectric polarizations of the AlGaN films are significantly reduced.     

Structural and conformational investigations in SmA and different SmC phases of new hockey stick-shaped compounds

New meta -substituted homologous three-ring mesogens, the 4-(3- n -decyloxyphenyliminomethyl) phenyl 4- n -alkyloxybenzoates, have been synthesized, which are non-linear due only to the attachment of one of the alkyloxy groups in a meta -position. The mesophases were studied by optical microscopy, differential scanning calorimetry, NMR spectroscopy, X-ray diffraction, and electro-optical and dielectric measurements. Unusual phase behaviour was observed on varying the length of the terminal chain. The most interesting finding is the occurrence of two polymorphic tilted smectic phases designated as SmC 1 and SmC 2 . The existence of these phases was revealed by calorimetric studies and also from the pronounced difference in optical textures. It was shown from NMR measurements that the molecular orientation changes from a synclinic to an anticlinic arrangement in the SmC 1 to SmC 2 phase transition. It has also been shown, using NMR, that the SmC 1 →SmC 2 phase transition in these compounds is accompanied by a conformational change in the molecular fragment containing the aromatic ring with the meta -substituted terminal alkyloxy chain. This conformational change is linked to a change in the shape of the molecules and leads to a different packing of the molecules within the layers of the SmC 2 phase. From dielectric measurements an increase by a factor of two was detected in the molecular mobility at the transition into the low temperature SmC 2 phase. This finding supports a change in the packing as result of conformational changes.     

Temperature and molecular weight dependence of fracture behaviour of polypropylene films

The effect of temperature on fracture behaviour of isotactic polypropylene films has been studied on two PP samples of molecular weights M_W=270 kg mol⁻¹ and M_W=150 kg mol⁻¹, using the Essential Work of Fracture method. Two ductile-brittle transitions as a function of temperature are in evidence at respectively 10 and 60 °C. The former transition occurs for the highest molecular weight and the latter one for the lowest molecular weight.

Three processes are involved in the temperature effect on PP toughness: (1) The decrease of yield stress with temperature according to Eyring’s law; (2) The role of cooperative motions in the amorphous phase: the ductile-brittle transition of the sample of highest M_W corresponds to the glass transition; and (3) The role of the mobility of the crystalline phase: the ductile-brittle transition of the sample of lowest M_W corresponds to the C transition.     

Halogen-Modulated Reversible Phase Transition in Organic-Inorganic Hybrid Perovskites

The tunable structure, abundant raw materials, and ease of preparation have made molecular dielectric crystals popular for use in device design. In spite of this, some known molecular switching materials have a low phase transition temperature and a low dielectric constant, which limit their applications. Therefore, designing and synthesizing molecular-based phase transition compounds with high phase transition temperature and superior properties is especially important. In this work, we use 3-chloropropan-1-ammonium hydrochloride and SbCl₃/SbBr₃ inorganic salts as building blocks to synthesize compounds (CPA)₂(BPA)₂Sb₂Br₁₀ ( 1 ) (CPA=3-chloropropan-1-ammonium, BPA=3-bromopropan-1-ammonium) and (CPA)₂Sb₂Cl₈ ( 2 ). Compound 1 has a high phase transition temperature (407.45 K). Dielectric measurements and differential scanning calorimetry (DSC) confirm the structural phase transition in compound 1 , and no fatigue decay is observed after several dielectric cycles. In addition, compounds 1 and 2 possess semiconductor properties. The findings of this study provide new directions for the design and application of multifunctional molecular dielectric materials.     

"分子行走理论"模型——分子熵的笼敝效应及其在有机酸碱性比较中的应用

基团的电子、共轭、超共轭、空间位阻、溶剂化等效应在有机酸碱理论及酸碱性分析中一直占据主导地位.但在气相状态下,分析某些物质的酸碱性时单用上述理论远不能满足要求,得不到与实验事实相符的结果.从热力学及分子统计力学角度出发,以量子化学为辅助,研究了分子熵值及其构象改变对物质酸碱性、反应活性、反应速率的影响.提出理想状态下"分子自由行走"、"自由均方行走距"等假设,并以此演绎出理想状态下有机分子构象改变所遵循的统计规律——"类自由结合链高斯模型".建立了"分子熵效应笼敝扩散"分子构象模型,用该理论成功解释了气相状态下甲、乙、丙、丁、戊、己酸酸性大小差异及气相氨、伯胺、仲胺、叔胺、苯胺、二苯胺的碱性差异.结果表明:自由均方行走距及分子笼敝大小是影响物质活性的关键因素.     

Effect of chirality on phase transitions in re-entrant liquid crystals

The phase diagrams for enantiomers and their racemic counterparts have been compared in order to determine the influence of chirality on re-entrant phenomena. It has been found that chirality affects the location of the partially bilayer SmAd and monolayer smectic SmA1 phase areas, while the position of the smectic X phase remains nearly unchanged. This result shows that the N-SmA phase transition is influenced by a molecular chiral discrimination effect. Moreover, in enantiomeric systems, a N* re1-N* re2 phase transition has been detected by DSC within the re-entrant nematic gap which is limited by the smectic Ad and the SmX phases. Based on preliminary data, the SmX phase seems to be either a weakly tilted SmC antiphase or an incommensurate orthogonal mesophase.