N-炔丙基酰胺共聚物组成对其光学活性的影响

通过与手性单体共聚,可调控基于非手性单体所制备的螺旋聚合物的光学活性。文中利用[Rh]金属有机催化剂,进行了手性(M1)和非手性(M2)N-炔丙基酰胺单体的共聚反应,聚合物产率高于97%。利用圆二色光谱技术及旋光仪对共聚物的光学活性进行了表征,发现共聚物组成对其光学活性有显著影响,不仅影响共聚物光学活性的大小,甚至还决定着聚合物主链所形成螺旋结构的手性。     

光致固液转变型偶氮苯聚合物的合成与光响应性能

偶氮苯聚合物由于其独特的光响应性能在光分子开关、信息存储等领域具有潜在的应用,但偶氮苯顺反异构化转变及光致固液转变的影响因素仍需要更深入的研究。文中设计并合成了4种偶氮苯聚合物,对比了偶氮苯相连的柔性链对其光响应性能的影响。研究发现,引入柔性链段使偶氮苯异构化时间从20 min降到100 s,同时含柔性链段的偶氮苯聚合物具有光致固液转变的能力,而不含柔性链段的偶氮苯聚合物不能发生光致固液转变。     

2，5-二烷氧基取代聚对苯撑热性能研究

采用DSC、TGA、WAXD研究了系列 2 ,5 二烷基取代聚对苯撑 (DAO PPP)的热稳定性、热氧化稳定性、相转变行为。DAO PPP的热分解由两步组成。在热分解温度超过 30 0℃时 ,首先开始发生侧链的断裂 ;温度超过 50 0℃时 ,聚合物主链才发生分解。实验结果表明 ,烷氧基的引入降低了聚合物的热稳定性 ,聚合物中的杂质和结构缺陷对其热稳定性也有一定的影响。在其DSC曲线上 ,没有观察到整个聚合物分子的熔点 ,但可观察到具有较长侧链的聚合物侧链的相转变行为。     

含天然产物侧基的取代聚乙炔的合成与性能

将天然产物如氨基酸、甾醇、核苷和糖类引入到取代聚乙炔侧链上,利用共轭多烯主链和功能性侧链的协同作用,聚合物表现出光学活性、液晶、刺激响应性、手性识别、生物相容性等新颖性能,在化学传感、信息储存、光学显示、手性探针、药物传递、组织工程等领域具有潜在的应用价值.文中综述了含天然产物分子侧基的取代聚乙炔衍生物的合成与性能,并...     

手性分子结构对嵌段共聚物自组装螺旋的影响

手性小分子诱导嵌段共聚物手性组装是构筑手性可控螺旋结构的一种有效方法,但是目前对手性小分子引导螺旋结构形成的机制还没有明确认识。文中利用具有不同化学结构的手性掺杂剂与聚1,4-丁二烯-b-聚环氧乙烷(PBd-b-PEO)共组装,研究了手性小分子化学结构的差异对螺旋结构形成的影响。通过小角散射、透射电镜和圆二色光谱证明了苹果酸和扁桃酸诱导嵌段共聚物中PEO形成螺旋相结构,而酒石酸二苄酯和二乙酰基酒石酸由于氢键位点和取代基效应无法诱导形成螺旋相结构。组装体由于聚合物结构变化和手性分子聚集态变化而呈现不同的手性信号变化规律。通过分子模拟分析了共组装体系中氢键缔合体的稳定性,从能量角度解释了手性分子结构对聚合物形成螺旋结构的影响。     

分子复合材料的研究进展

分子复合材料是指刚性高分子链(段)聚合物与柔性链聚合物(树脂)共混，刚性链高分子聚合物作为增强相在接近分子水平上均匀分散在柔性链(段)树脂基体中，达到最佳分子增强效应，形成高强度、高模量的复合材料。制备分子复合材料的关键在于溶混性。文中重点讨论了分子复合材料的制备方法与改进方法，简要介绍了分子复合材料的分类、特点及组成。     

手性丙烯酸酯侧链液晶共聚物的正电子湮没寿命谱研究

用正电子湮没寿命谱研究了手性丙烯酸酯侧链液晶共聚物分子主链与介晶基元侧链的运动行为及相互作用。结果表明，侧链液晶基元的取向随磁场强度增加而增加，当磁场强度达到一定值后则趋于恒定。侧链介晶基元受磁场的诱导取向对分子主链运动的影响为非线性效应。     

聚(酰亚胺-酯)热致性液晶高分子的合成与表征EI

以Ｎ，Ｎ′－二（ω－羟乙基）苯均四甲酰二亚胺和４，４′－（α，ω－烷亚甲基二酰氧）苯甲酰氯为单体，通过溶液缩聚反应合成了含不同柔性链长的主链型液晶高分子。聚合物的液晶行为用ＤＳＣ、偏光显微镜和Ｘ衍射法进行了表征。发现所有的聚合物均有较好的结晶性和随分子中柔性链段长度的改变聚合物的相变温度呈规律性的变化。     

2，5—二烷氧基取代聚对苯撑热笥能研究

采用DSC,TGA,WACD研究了系列2,5－二烷基取代聚对苯撑（DAO－PPP）的热稳定性,热氧化稳定性,相转变行为,DAO－PPP的热分解由两步组成,在热分解温度超过300℃时,首先开始发开侧链的断裂,温度超过500℃时,聚合物主要链才发生分解,实验结果表明,烷氧基的引入降低了聚合物的热稳定性,聚合物中的杂质和结构缺陷对其热稳定性也有一定的影响,在其SAC曲线上,没有观察到整个聚合物分子的熔点,但观察到具有较长侧链的聚合物侧链的相转变行为。     

含磺酸甜菜碱的温敏聚合物胶束的制备及胶束温敏性EI北大核心CSCD

首先通过炔丁醇与2-溴异丁酰溴的酯化反应得到了一种带有炔基的ATRP引发剂,然后用其引发异丙基丙烯酰胺得到PNIPAm-alkyne,再通过点击反应将带有炔基的PNIPAm-alkyne接枝到侧链含有叠氮基团的聚己内酯-聚(甲基丙烯酸二乙氨基乙酯/N,N-二乙氨基甲基丙烯酸硫代甜菜碱酯)(P(CL-ACL)-b-PDEAS)上得到P(CL-g-PNIPAm)-PDEAS。通过核磁、红外、凝胶渗透色谱对聚合物的组成进行了分析,PNIPAm-alkyne的相对分子质量为5500和8300,相对分子质量分布为1.18和1.24,表明这种方法制备的聚合物相对分子质量及分布能够得到较好的控制。PNIPAm-alkyne点击到P(CL-ACL)30-PDEA7S3上制备的聚合物胶束的透射率随着温度的升高而降低,粒径亦由40 nm变到63 nm,并从透射电镜的结果分析了胶束表面高分子链发生构象转变,从而证实成功地制备了一种具有温敏特性的含有聚磺酸甜菜碱的聚合物胶束。     

Model systems for single molecule polymer dynamics

Double stranded DNA (dsDNA) has long served as a model system for single molecule polymer dynamics. However, dsDNA is a semiflexible polymer, and the structural rigidity of the DNA double helix gives rise to local molecular properties and chain dynamics that differ from flexible chains, including synthetic organic polymers. Recently, we developed single stranded DNA (ssDNA) as a new model system for single molecule studies of flexible polymer chains. In this work, we discuss model polymer systems in the context of "ideal" and "real" chain behavior considering thermal blobs, tension blobs, hydrodynamic drag and force-extension relations. In addition, we present monomer aspect ratio as a key parameter describing chain conformation and dynamics, and we derive dynamical scaling relations in terms of this molecular-level parameter. We show that asymmetric Kuhn segments can suppress monomer-monomer interactions, thereby altering global chain dynamics. Finally, we discuss ssDNA in the context of a new model system for single molecule polymer dynamics. Overall, we anticipate that future single polymer studies of flexible chains will reveal new insight into the dynamic behavior of "real" polymers, which will highlight the importance of molecular individualism and the prevalence of non-linear phenomena.     

Photoinduced fabrication of complex surface relief structures on azobenzene functionalized polymers

Light induced fabrication of complex surface relief structures on azobenzene functionalized polymers is reported. Large class of side chain and main chain polymers can be utilized to record these relief structures. The recording and erasure process are strongly dependent on the polarization. Possible transport mechanism of polymer chains well below the glass transition temperature due to photoinduced effect is discussed.     

手性导电高分子聚合物的研究进展

手性导电高分子聚合物在手性高分子领域里有很多独特的化学性质,已成为功能材料领域的研究热点。综述了聚苯胺、聚吡咯和聚噻吩等一些经典手性导电高分子聚合物的合成途径:当共轭的导电聚合物链上带有对映体纯取代基或有手性的掺杂阴离子时,其光学活性可以被π-π*电子吸收带所诱导;阐述了它们的合成发展史、现状、显著特性及手性导电高聚合物的应用前景。     

具有光学活性高性能高分子材料的研究进展

旋光性聚合物可以使通过它的偏振光发生偏转,在手性识别和对映体拆分、手性催化剂、液晶、生物医药、光学开关和非线性光学等领域展现出良好的应用前景。本文综述了几种利用旋光性单体缩聚合成具有光学活性高分子材料的方法,对所得聚合物的热稳定性、可溶性、旋光性等主要性能进行分析比较,得到一系列重要的结论,并对其影响机理进行讨论。在此...     

Exploring time-dependent structural changes during the cold crystallization process of isotactic polystyrene by infrared spectroscopy and multivariate curve resolution

The present study attempts an application of Fourier transform infrared (FT-IR) spectroscopy in conjunction with multivariate curve resolution (MCR) techniques to explore the structural evolution of isotactic polystyrene (iPS) during the cold crystallization process. The focus of the present study is placed on the performance of MCR techniques, e.g., orthogonal projection (OP), alternating least squares (ALS), and fixed-size moving window evolving factor analysis (FSMWEFA), and the interpretability of spectral changes in the investigated chemical process. As a result, valuable information and conclusions about the structural evolution of iPS during the crystallization process can be extracted: when the amorphous phase of iPS changes, the ordering of the phenyl rings takes place first, and then the polymer chains adjust their local conformations to form short 3(1) helix structures. Furthermore, according to intensity profiles of the spectral variations, the ordering of the phenyl rings proceeds more intensely than the formation of ordered local chains, and the structural evolution of iPS occurs even during the induction period. The spectral variations resulting from the conformational changes in the 3(1) helical structures depend on the sequence length of the helical chains: the longer the polymer chain is, the smaller the corresponding band variations are. It has been demonstrated that the combination of FTIR spectroscopy and chemometric MCR techniques is very promising for the analysis of the crystallization process of polymers. MCR is a powerful tool for analyzing and visualizing spectral data and integrating them with other information, making spectral intensity variations more amenable to interpretation in order to explore the molecular dynamics of polymers.     

Influence of polarity on filling polymer molecules into carbon nanotubes

Using molecular dynamics (MD) simulation, we studied the influence of polarity of polymer chains and modified single-walled nanotubes (SWNTs) on filling polymer chains into SWNTs. The center of mass (COM) distance and the interaction energy between the polymer molecules and SWNTs, as well as non-bond energy (including van der Waals energy and electrostatics energy) differences (ΔE) between initial structure and final structure in the SWNTs–polymers systems were calculated. The simulations indicate that both the polarity of polymer molecules and the polarity of modified groups attached to SWNTs can obstruct filling polymer chains into SWNTs. The general conclusions may be of importance in the production of high-performance SWNTs–polymers nanocomposites and have important theoretical significance on the application of carbon nanotubes as drug carrier and transportation channels.     

Cyclodextrin Insulation Prevents Static Quenching of Conjugated Polymer Fluorescence at the Single Molecule Level

Conjugated polymers (CPs) are promising materials for fluorescence imaging application. However, a significant problem in this field is the unexplained abnormally low fluorescence brightness (or number of fluorescence photons detected per one excitation photon) exhibited by most of CP single chains in solid polymer hosts. Here it is shown that this detrimental effect can be fully avoided for short chains of polyfluorene‐bis‐vinylphenylene (PFBV) embedded in a host polymer matrix of PMMA, if the conjugated backbone is insulated by cyclodextrin rings to form a polyrotaxane (PFBV‐Rtx). Fluorescence kinetics and quantum yields are measured for the polymers in liquid solutions, pristine films, and solid PMMA blends. The fluorescence brightness of PFBV‐Rtx single chains dispersed in a solid PMMA is very close to that expected for a chain with 100% fluorescence quantum yield, while the unprotected PFBV chains of the same length possess 4 times lower brightness. Despite this, the fluorescence decay kinetics are the same for both polymers, suggesting the presence of static or ultrafast fluorescence quenching in the unprotected polymer. About 80% of an unprotected PFBV chain is estimated to be completely quenched. The hypothesis is that the cyclodextrin rings prevent the quenching by working as ‘bumpers’ reducing the mechanical forces applied by the host polymer to the conjugated backbone and help retaining its conformational freedom. While providing a recipe for making CP fluorescence bright at the single‐molecule level, these results identify a lack of fundamental understanding in the community of the influence of the environment on excited states in conjugated materials.     

Investigation of the optical properties of polyfluorene/ZnO nanocomposites

Polyfluorene (PF) and its derivatives are very promising candidates for organic light emitting diodes (OLEDs) in lighting applications because of their high photoluminescence and electroluminescence efficiencies. Recent investigations of potential materials for OLEDs have shown that introducing n-type inorganic nanoparticles into conjugated polymers is efficient to produce stable and high performance devices. In this study, composite thin films made by incorporation of zinc oxide (ZnO) nanoparticles into a PF derivative have been prepared and their optical properties have been investigated.The prepared thin films were stored in different media (in air, in vacuum, in the dark or exposed to light) in order to study environmental influences on the material stability. Analysis of spectral data obtained from infrared (IR), Raman, UV-vis, and photoluminescence (PL) measurements shows a large enhancement in luminescence for polymer nanocomposites while using high nanoparticle concentrations (within a limit of 10% ZnO). Time-resolved PL performed on those nanocomposite films corroborated the above result: it indicated that the light-emission enhancement can be explained by efficient energy transfer from nanoparticles to the polymer chains and increase of the chain separation distance. In addition, the nanocomposites were found to be more stable than pristine polymer films whatever the storage conditions were used. It was confirmed by IR analysis that incorporation of nanoparticles into polymers prohibited the formation of fluorenonyl groups in PF chains, which was identified as the main cause of the degradation of the polymer under photo-oxidation.     

Polymers with Side Chain Porosity for Ultrapermeable and Plasticization Resistant Materials for Gas Separations

Polymer membranes with ultrahigh CO₂ permeabilities and high selectivities are needed to address some of the critical separation challenges related to energy and the environment, especially in natural gas purification and postcombustion carbon capture. However, very few solution‐processable, linear polymers are known today that access these types of characteristics, and all of the known structures achieve their separation performance through the design of rigid backbone chemistries that concomitantly increase chain stiffness and interchain spacing, thereby resulting in ultramicroporosity in solid‐state chain‐entangled films. Herein, the separation performance of a porous polymer obtained via ring‐opening metathesis polymerization is reported, which possesses a flexible backbone with rigid, fluorinated side chains. This polymer exhibits ultrahigh CO₂ permeability (>21 000 Barrer) and exceptional plasticization resistance (CO₂ plasticization pressure > 51 bar). Compared to traditional polymers of intrinsic microporosity, the rate of physical aging is slower, especially for gases with small effective diameters (i.e., He, H₂, and O₂). This structural design strategy, coupled with studies on fluorination, demonstrates a generalizable approach to create new polymers with flexible backbones and pore‐forming side chains that have unexplored promise for small‐molecule separations.     

Synthesis,processing sand properties of thermotropic liquid-crystal polymers

Thermotropic liquid-crystal polymers for high-performance applications are typically based on wholly aromatic polyester and polyamide architectures. The linear character of the aromtic monomers produces polymer chains with stiff, extended conformations. As a result, the chains organize themselves into a nematic melt and readily orient in response to processing flow fields. The close coupling between chain orientation and flow fields produces both a rich variety of materials and a high degree of controllability of their structure and properties (such as the tensile strength, elastic modulus and coefficient of thermal expansion). In this paper, we describe synthetic efforts to develop liquid-crystal polymer structures and the relationships between chain molecular structure, processing, and properties of this class of polymers in two distinct processing situations: Injection molding and fiber formation. The special importance of the orientational flow field in developing high orientation and excellent mechanical properties will be highlighted.