Synthesis of Dendronized Aromatic Polyamides with Chloromethyl Groups in the Periphery by Macromonomer Approach

The preliminary results for one-pot synthesis of dendronized aromatic polyamides with chloromethyl groups in the periphery by approach were reported first time. The GPC analysis of the resulting dendronized polymers has shown typical weight average molecular weight （Mw） of 41554 and a polydispersity of 2.74.

Synthesis and characterization of dendronized poly(methylsiloxane) with appendent Fréchet-type dendrons

A new kind of dendronized poly(methylsiloxane) (3a and 3b) with appendent Fréchet-type poly(aryl ether) dendrons has been synthesized and characterized by GPC, DSC, TGA, fluorescence and UV-Vis spectra.

Amphiphilic dendronized homopolymers

A series of second generation of amphiphilic dendronized homopolymers are efficiently synthesized,and their thermoresponsiveness in aqueous solutions and secondary structures in methanol solutions are described.These polymers are constructed in each repeat unit with various generations of hydrophobic 4-aminoproline and hydrophilic oligoethylene glycol (OEG)-based dendrons,and their over-all hydrophilicity is tuned by varying these dendron generations.Polymers with or without the first generation of proline dendron show good water solubility at room temperature,but exhibit typical thermoresponsive behaviors at elevated temperatures as characterized by turbidity measurements using UV-vis spectroscopy,while the polymer with the secondary generation of proline dendron is not soluble in water.All polymers show ordered secondary structures as evidenced by the optical rotation and circular dichroism experiments.Finally,assembly of these amphiphilic homopolymers into porous films via breath figure (BF) technique is described,and polymer structures are found to show significant influence on the morphology of porous film.

Synthesis and characterization of dendronized hyperbranched polymers through the “A_3+B_2” approach

Dendronized hyperbranched polymer （DHP） is a new kind of polymer, which combines the advantages of dendrimers and hy- perbranched polymers. In this work, two dendronized hyperbranched polymers, DttPG0 and DHPG1, were successfully pre- pared through the simple ＂A3＋B2＂ type Sonogashira coupling reaction. The nonlinear optical （NLO） effects of DHPG0 and DItPG1, characterized by the d33 values, were 183 and 220 pm V-1 respectively, higher than those of their analogues of den- dronized polymers and dendrimers, thanks to the special topological structure. Also, the obtained polymers displayed excellent solubility, good processability, and high thermal stability.

Dendronized Polymers with High FTC-chromophore Loading Density:Large Second-order Nonlinear Optical Effects, Good Temporal and Thermal Stability

In this study,two new dendronized nonlinear optical(NLO)polymers were synthesized with high FTC chromophore loading density by introduction of high generation chromophore dendrons on the side chains.Due to their suitable molecular weights,both of them possessed good solubility in common solvents.They also inherited the advantages of dendrimers(large NLO coefficient),especially for PG2 whose NLO coefficient d33 value was as high as 282 pm·V^–1.Also,PG2 had a good temporal stability with 80%of its maximum value being retained at the temperature as high as 129℃.

Interfacial assembly and host-guest interaction of anthracene-conjugated L-glutamate dendron with cyclodextrin at the air/water interface

The interracial assembly of photo-induced dimerization of atypical anthracene-containing amphiphilic dendron and host-guest interaction with γ-cyclodextrin has been investigated. It has been proved that even without long alkyl chain the amphiphilic dendron could still form stable Langmuir monolayer at the air/water interface. Through the host-guest interaction,γ-cyclodextrin can be used to encapsulate two headgroups of amphiphilic dendron in the antiparallel direction. However, the formed host-guest complex was sensitive to the surface pressure. Slight compression of surface pressure led amphiphilic dendron to reassemble into nanofibers through the strong π-π stacking between headgroups. On the other hand, under in situ irradiation, the amphiphilic dendron was stabilized in the cavity of γ- cyclodextrin through headgroup dimerization and the host-guest complex further irregularly aggregated to nanoparticles. Meanwhile, γ-cyclodextrin, as a silencer, blocked the supramolecular chirality transfer. Our conclusion was demonstrated through UV/vis, FT-IR, CD spectrum and AFM images, respectively.

Thermoresponsive dendronized copolymers for protein recognitions based on biotin-avidin interaction

Thermoresponsive biotinylated dendronized copolymers carrying dendritic oligoethylene glycol（OEG）pendants were prepared via free radical polymerization,and their protein recognitions based on biotin-avidin interaction investigated.Both first（PG1） and second generation（PG2） dendronized copolymers were designed to examine possible thickness effects on the interaction between biotin and avidin.Inherited from the outstanding thermoresponsive properties from OEG dendrons,these biotinylated cylindrical copolymers show characteristic thermoresponsive behavior which provides an envelope to capture avidin through switching temperatures above or below their phase transition temperatures（T_（cp）s）.Thus,the recognition of polymer-supported biotin with avidin was investigated with UV/vis spectroscopy and dynamic laser light scattering.In contrast to the case for PG1,the increased thickness for copolymer PG2 hinders partially and inhibits the recognition of biotin moieties with avidin either below or above its T_（cp）.This demonstrates the significant architecture effects from dendronized polymers on the biotin moieties to shift onto periphery of the collapsed aggregates,which should be a prerequisite for protein recognition.These kinds of novel thermoresponsive copolymers may pave a way for the interesting biological applications in areas such as reversible activity control of enzyme or proteins,and for controlled delivery of drugs or genes.

Synthesis and characterization of novel redox-active percec-type dendrons

Three novel redox-active percec-type dendrons were synthesized by mucleophilic substitution reaction of 11-bromoundecyl ferrocene and substituted benzoate.All the resultant ferrocenyl-modified dendrons were confirmed through FT-IR,NMR,and elemental analysis,etc.Furthermore,the thermal properties and electrochemical behavior of these dendrons were monitored with thermogravimetry analysis（TG）,differential scanning calorimetry（DSC）,polarized optical microscope（POM）,and cyclic voltammetry（CV）. Abound phase behavior and reversible electrochemical redox reaction process in the DMF solution of these dendrons was observed.

Thermoresponsive Nanogels from Dendronized Copolymers for Complexation,Protection and Release of Nucleic Acids

A series of thermoresponsive cationic dendronized copolymers and their corresponding nano gels containing den dritic oligoethylene glycol(OEG)units and guanidine groups were prepared,and their complexation,protect!on,and release of nucleic acids were investigated.The dendritic OEGs endow these copolymer materials with good biocompatibility and characteristic thermoresponsiveness,while cationic guanidine groups can efficiently bind with the nucleic acids.The dendritic topology also affords the copolymers specific shielding effect which plays an essential role in protecting the activity of nucleic acids.At room temperature,dendronized copolymers and the corresponding nanogels could efficiently capture and condense the nucleic acids,while above their cloud points(Tcps),more than 75%of siRNA could be released in 1 h triggered by ATP.More importantly,the copolymer showed protective capability to siRNA,while nano gels exhibit even better protection when compared to the copolymers due to the synergetic effect from the three-dimensional cross-linked network and high density of dendritic units in vicinity.This kind of smart dendr on ized copolymer nano gels form a no vel class of scaffolds as promisi ng materials for biomedical applicatio ns.

A second-order nonlinear optical dendronized hyperbranched polymer containing isolation chromophores： achieving good optical nonlinearity and stability simultaneously

Large nonlinear optical(NLO) coefficient and good stability, two essential factors to evaluate second-order NLO materials, are difficult to be achieved in one molecule simultaneously. Herein, by utilizing the concept of "isolation chromophore", "isolation group" and dendritic structure, a dendritic molecule D-NS and a dendronized hyperbranched polymer DHP-NS are prepared to investigate their structure-property relationship. For the small dendritic molecule D-NS, it exhibits a high d33 value of 140 pm/V.But this value can be easily dropped when the temperature is higher than 50 °C, which extremely limits its real application. After introducing D-NS into a dendronized hyperbranched polymer chains, the obtained DHP-NS also shows a high d33 value of101 pm/V, but much better stability than D-NS. Even when its thin film was heated to 120 °C, no obvious decay can be observed in the d33 value of DHP-NS. This work demonstrates an effective strategy to realize both large NLO effect and good stability simultaneously.

Design, synthesis and nonlinear optical properties of “dendronized hyperbranched polymers”

A new type of dendritic polymer, named dendronized hyperbranched polymer (DHP), was prepared successfully by the macro-monomer approach. Thanks to the perfect 3D isolation effects, DHPG1 exhibited good NLO property with d 33 value of 133 pm/V, higher than its analogues of dendronized polymer and dendrimer, and its stability of NLO effect was also enhanced.

Poly(benzyl ether) dendrons without conventional gelation motifs as a new kind of effective organogelators

Two poly(benzyl ether) dendrons,decorated in their periphery with nitrile groups,were divergently synthesized and fully characterized.Their gelation properties were studied by using scanning electron microscopy(SEM),X-ray crystal structure analysis and concentration-and temperature-dependent 1 H NMR spectroscopy.It was found that the gelation capability of these dendrons was highly dependent on dendron generation,and the second-generation dendron G 2-CN proved to be highly efficient organogelator despite the lacking of any conventional gelation motifs,such as amides,long alkyl side chains and steroidal groups.The multiple strong-stacking interactions and hydrogen bonding interactions due to the peripheral isophthalonitrile motifs were proved to be the main driving forces to form the self-assembled gel.

Self-assembly of insulated molecular wires of a water-soluble cationic PPV and anionic dendrons

Insulated molecular wires of poly(phenylenevinylene) (PPV) were prepared by wrapping the conjugated backbones with dendrons through a noncovalent approach. It was found that electrostatic interaction between the quaternary ammonium groups of PPV-1 and the carboxylate moieties in dendrons induced the packing of dendrons along PPV-1 conjugated backbones. Absorption and emission spectroscopic examinations in solution and solid film indicated that the PPV-1 backbones adopted a more planar and isolated conformation in the complexes. Furthermore, interchain interactions in the complexes could be greatly reduced, improving the quantum yield of PPV-1.

A CONFORMATION STUDY OF POLYELECTROLYTE-DENDRITIC SURFACTANT COMPLEXES IN DILUTE SOLUTIONS

Three dendronized polymers from generation one to generation three have been prepared by complexing negatively charged Frechet-type dendrons with a polyanion, poly（diallydimethylammoniurn chloride） （PDADMAC）. The gaffing degree has been confirmed mainly by elemental analysis. In dilute solutions of tetrahydrofuran, static light scattering studies indicate that the first generation complex has a coil-like conformation, even more flexible than PDADMAC. The second and third generation complexes exhibit polyelectrolyte behavior. Dynamic light scattering experiments indicate that all the three complexes have almost the same hydrodynamic radius, indicating that they might own similar coil conformation. Atomic force microscopy shows the existence of disordered globules formed by one or a couple of complex coils. All these observations can be explained by the flowerlike coil conformation, which is formed by the intra-molecular association. This is totally different from the stretched chain conformation formed by covalently connected dendronized polymers. This result also explains why some ordered supramolecular structures, found in condensed state of the similar complexes, are not as perfect as those of conventional dendronized polymers.

树形分子疏水改性聚氨酯缔合增稠剂的合成及在乳液中的流变行为

以不同烷氧基取代的Percec型苯甲醇树形分子作为封端剂,制备3种具有相同亲水链段但末端疏水尾链数不同的聚氨酯缔合增稠剂(HEURs):HEUR-1C10(单尾)、HEUR-2C10(双尾)和HEUR-3C10(三尾)。通过红外光谱和凝胶渗透色谱对HEURs的结构和相对分子质量进行了表征,并采用应力控制型流变仪研究了不同HEUR添加量的纯丙乳液的稳态及动态剪切行为。结果发现:二取代和三取代树形分子封端的HEUR-2C10和HEUR-3C10的增稠效果明显好于普通单疏水尾链封端的HEUR-1C10。这表明在亲水链段相同时,短而多的疏水链有利于增加有效网链密度,使得相邻胶束和乳液粒子之间产生更多的桥连,形成更强的疏水网络结构。本研究为新型高效聚氨酯增稠剂的制备与应用提供了有益的借鉴。

剪切作用对聚合物溶液流体力学半径分布特征的影响研究

采用近井地带剪切装置及动静态光散射仪研究不同浓度HAWP聚合物溶液、HDP树枝状聚合物溶液在不同剪切强度下的流体力学半径分布特征,并结合粘度、浓度、重均分子量、阻力系数与残余阻力系数的测定探索聚合物溶液粒径分布对宏观流变性和驱替性能的影响。结果表明,具有支化状结构的HDP聚合物在水溶液中的流体力学半径以"极差大"、"数量均匀"、"分布宽"等特征分布,剪切前后峰形均呈现"帽子型"单峰或微弱双峰趋向三峰模式。HAWP聚合物溶液主峰粒径随着浓度升高增大且所占总粒径比例不断增高,而HDP树枝状聚合物溶液主要以分布变宽为主,主峰粒径及所占总粒径比例一直较为均一。剪切作用使HAWP聚合物溶液的粒径分布特征以单峰明显裂变为尖锐双峰模式为主,而HDP聚合物溶液峰型裂变程度相对微弱。

树枝化对聚芴类分子发光行为的影响

运用稳态吸收、稳态荧光光谱及皮秒时间分辨荧光光谱等手段,研究了树枝化对聚芴分子的光谱动力学行为的影响.在1×10-5mol/L四氢呋喃溶液中,非树枝化聚芴和不同代数的树枝化聚芴的稳态吸收和稳态荧光光谱基本一致,表明树枝化不影响聚芴基团的本征电子性质;在薄膜状态下,紧密排列的聚芴分子表现出明显的链间聚集行为.不同代数树枝化聚芴的时间分辨荧光动力学研究结果表明,溶液状态下的发光为单指数衰减行为,而薄膜状态下的发光为多指数衰减行为,且其发光寿命随树枝化代数增加而增长,表明树枝化基团抑制了邻近的聚芴分子之间能量传递所致的激发态能量耗散.

树枝状侧基型聚合物的合成及其溶液性质

以乙二胺、丙烯酸甲酯、丙烯酰胺为原料,通过丙烯酰胺及丙烯酸甲酯自由基聚合反应合成聚合物主链,主链酯基为侧基反应中心,利用乙二胺与丙烯酸甲酯交替发生的酰胺化反应以及Michael加成反应合成树枝状侧基,制备了一种新型树枝状侧基型聚合物,并利用红外光谱(FTIR)、凝胶色谱(GPC)、扫描电镜(SEM)进行表征。最佳合成条件:反应温度30℃,反应时间24～48 h,反应物摩尔比1∶1。对合成聚合物的水溶液性质进行了评价,增黏能力较改性前提高了3倍;高温、高矿化度下黏度保持率较改性前分别提高了50%与80%,表现出良好的抗温抗盐性,达到了分子结构设计的预期效果。

树枝化聚合物的合成、结构表征及其应用

本文综述了由树枝状大分子和线形聚合物结合而形成的一类新型树形聚合物———树枝化聚合物的研究进展 ,包括树枝化聚合物的各种合成方法、结构表征和形态分析等。同时对树枝化聚合物在催化载体、纳米材料、生化和光电功能材料等领域的应用研究进行了详尽的综述。

支化结构对树枝状聚合物静态吸附特征的影响

采用浸泡法研究了不同支化程度的驱油用树枝状聚合物在石英砂上的静态吸附特征,并利用动静态激光光散射仪和环境扫描电子显微镜测定了聚合物溶液的分子尺寸和微观结构。结果表明,不同支化程度的树枝状聚合物溶液的等温吸附曲线均呈现三段式的吸附特点;在初始阶段,支化结构小的聚合物支链条数较少以及流体力学半径较小,其在固定表面积的石英砂上吸附位阻比支化结构大的聚合物小,导致吸附量较大;在吸附形式为多层吸附的Ⅱ、Ⅲ阶段,支化程度大的聚合物支化链间相互作用越强,易缠结形成网络结构,致使其在石英砂表面吸附层数多,吸附量比支化程度小的聚合物多。