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.

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.

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.

Functional Surfactants for Molecular Fishing,Capsule Creation,and Single-Cell Gene Expression

Creating a single surfactant that is open to manipulation,while maintaining its surface activity,robustness,and compatibility,to expand the landscape of surfactant-dependent assays is extremely challenging.We report an oxidation-responsive precursor with thioethers and multiple 1,2-diols for creating a variety of functional surfactants from one parent surfactant.Using these multifunctional surfactants,we stabilize microfluidics-generated aqueous droplets.The droplets encapsulate different components and immerse in a bioinert oil with distinct interfaces where an azide-bearing surfactant allow fishing of biomolecules from the droplets,aldehyde-bearing surfactant allow fabrication of microcapsules,and hydroxyl-bearing surfactants,with/without oxidized thioethers,allow monitoring of single-cell gene expression.Creating multifunctional surfactants poses opportunities for broad applications,including adsorption,bioanalytics,catalysis,formulations,coatings,and programmable subset of emulsions.

AN EXPERIMENTAL STUDY OF THE ANTIHSV-Ⅱ ACTION OF 500 HERBAL DRUGS

Experimental assessments were made on the anti-HSV-Ⅱ action of 500 herbs by determinations of thevirus inhibition logarithm(VIL).13 highly effectiveherbs (VIL■4.00)were screened cut,providing a ra-tional basis for clinical therapy.Among these effec-tive herbs,10 were aqueous extracts of Artemisiaanomala,Centella asiatica,Epimedium Sagittatum,Hibiscus mutabills,Hosta plantaginea,Hypericumjaponicum,Inula japonica.Mosla punctata,Rhodo-dendron simsii,and Rhus chinenses,while 3 werealcohol extracts of Epimedium Sagittatum,Hypericumjaponicum,and Mosla punctata.

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.

克隆红宝石喜林芋

红宝石喜林芋,学名philoden-dron crubescens"Red Emerald",天南星科,喜林芋属。属名来自希腊词的philos(喜爱)和dendron(树木),意指这种植物喜欢攀缘树木生长。种名为变红的意思,又名红柄喜林芋。传统的繁殖方法为分株繁殖和扦插等。根据它繁殖率偏低、速度慢,同时繁殖受季节的限制等特点,

Synthesis of Helical Poly(phenylacetylene)s Carrying Dendritic Pendants with Varied Branching Densities Through Polymerization in Different Solvents

Helical poly(phenylacetylene)s(PPAs)have received extensive attention because of their features in dynamic chirality and promising applications.Therefore,understanding relationship among the polymer molecular structures,polymerization conditions and tunability of their chirality is of key scientific value.Recently,we developed a novel class of dendronized PPAs carrying 3-fold dendritic oligo(ethylene glycols)(OEGs)via alanine linkage,and found that these bulky polymers exhibited tunable helical conformations through thermally-mediated dehydration and aggregation.Herein,we report on synthesis of a homologous series of dendronized PPAs that carry 2-fold,3-fold or 6-fold dendritic OEG pendants,and focus on effects of molecular topological structures,peripheral units and polymerization solvents on the thermoresponsiveness and their conformation switching behaviors.Effects of branching density and peripheral units(ethoxyl or methoxyl)of the dendritic OEG pendants were examined,and found to play a decisive role on the helical conformation and thermoresponsiveness of these dendronized PPAs due to their different bulkiness and overall hydrophilicity.In addition,different polymerization solvents were checked for their possible influence on the polymerization,thermoresponsive behavior and the chirality of the resulting polymers.For polymerization in selective solvents like water or methanol,the obtained dendronized PPAs exhibited weak thermal transitions,while polymerization in non-selective solvent like THF furnished PPAs with characteristic thermoresponsive behavior,indicating that solvents were involved in the process of polymerization of the dendronized macromonomers.More interestingly,different chiralities of the PPAs through polymerization in various solvents were retained,irrelevant to the purification process and solvents treatments.This work suggests that the topological structures together with polymerization solvents can modulate the thermoresponsive behavior and helical conformation of the dendronized PPAs.

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.

Group actions on treelike compact spaces

We show that group actions on many treelike compact spaces are not too complicated dynamically.We first observe that an old argument of Seidler(1990)implies that every action of a topological group G on a regular continuum is null and therefore also tame.As every local dendron is regular,one concludes that every action of G on a local dendron is null.We then use a more direct method to show that every continuous group action of G on a dendron is Rosen thal represent able,hence also tame.Similar resul ts are obtained for median pretrees.As a related result,we show that Helly's selection principle can be extended to bounded monotone sequences defined on median pretrees(for example,dendrons or linearly ordered sets).Finally,we point out some applications of these results to continuous group actions on dendrites.

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.