α‐Methoxy‐ω‐alkyne poly(ethylene glycol) (PEG) was tagged with pendent N‐hydroxy‐succinimidyl activated esters by photografting of a molecular clip. This easily synthesized heterofunctional PEG was found to be a versatile building block for (i) conjugation with an amino derivative and (ii) grafting to azido functional aliphatic polyesters backbone by Huisgen's 1,3‐dipolar cycloaddition. This original combination of “clip” and “click” reactions provides a versatile and straightforward pathway for the synthesis of functional amphiphilic and degradable copolymers valuable for biomedical applications such as in drug‐delivery.
The successful encapsulation of reactive components for the azide/alkyne‐“click”‐reaction is reported featuring for the first time the use of a liquid polymer as reactive component. A liquid, azido‐telechelic three‐arm star poly(isobutylene) ( = 3900 g · mol−1) as well as trivalent alkynes were encapsulated into micron‐sized capsules and embedded into a polymer‐matrix (high‐molecular weight poly(isobutylene), = 250 000 g · mol−1). Using (CuIBr(PPh3)3) as catalyst for the azide/alkyne‐“click”‐reaction, crosslinking of the two components at 40 °C is observed within 380 min and as fast as 10 min at 80 °C. Significant recovery of the tensile storage modulus was observed in a material containing 10 wt.‐% and accordingly 5 wt.‐% capsules including the reactive components within 5 d at room temperature, thus proving a new concept for materials with self‐healing properties.
Summary: Three‐dimensional polyaniline (PANI) nanowire networks were synthesized in high yield using a “soft template” self‐assembled with hexadecyltrimethylammonium bromide and oxalic acid. The PANI nanowire networks had diameters from 35–100 nm depending on synthesis conditions and/or procedures. The networks and the “cross‐linking points” were clearly observed by field‐emission scanning electron microscopy and transmission electron microscopy. A possible mechanism for the formation of three‐dimensional PANI nanowire networks is discussed.
FESEM image of PANI with three‐dimensional nanowire networks. 相似文献
The synthesis of P(VA‐co‐VAc)‐graft‐PDMS copolymers has been achieved in microsuspension by direct reaction between an epoxy‐terminated PDMS and some pendant alcohol groups in P(VA‐co‐VAc). In this synthesis, the copolymer is used both as dispersant and reactant. The hydrophilic/hydrophobic character of the final material can be varied at will by incorporating various contents of epoxy‐functionalized PDMS through optimized reaction conditions. The final composition was determined by TGA and 1H NMR. Products prepared from monofunctional PDMS were easily redispersed in water whereas a film of crosslinked materials, arising from difunctional PDMS, showed the best waterproofing as shown by contact angle analysis.
This paper focuses on the attachment of densely grafted polymer layers (polymer brushes) to various inorganic and polymeric substrates by the “grafting to” method. A brief overview of synthesis of polymer brushes by the method is first provided, with emphasis on chemical approaches to polymer attachment. The second part of the paper covers the synthesis of polymer layers via a recently developed macromolecular anchoring layer approach. Several examples of application of the grafting technique are presented for generation of hydrophobic, hydrophilic, gradient, and switchable surfaces.
Hybrid nanoparticles with a silica core and grafted poly(methyl methacrylate) (PMMA) or poly(n‐butyl methacrylate) (PBMA) chains were prepared via activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) at room temperature under high pressure. Due to enhanced propagation rate constant and reduced termination rate constant for polymerizations conducted under high pressure, the rate of polymerization was increased, while preserving good control over polymerization when compared to ATRP under ambient pressure. Molecular weights of greater than 1 million were obtained. The PMMA and PBMA brushes exhibited “semi‐diluted” or “diluted” brush architecture with the highest grafting densities ≈0.3 chain·nm−2.
The identification and control of a critical stage of polyaniline “nanotube” self‐assembly is presented, namely the granular agglomeration or growth onto nanorod templates. When the synthesis pH is held above 2.5, smooth insulating nanorods exhibiting hydrogen bonding and containing phenazine structures are produced, while below pH 2.5, small 15–30 nm granular polyaniline nanoparticles appear to agglomerate onto the available nanorod surface, apparently improving conductivity of the resulting structures by three orders of magnitude. This finding affects both fundamental theories of polyaniline nanostructure self‐assembly and their practical applications.
A new series of azobenzene‐containing polyfluorenes have been successfully prepared through polymer reactions by the utilization of “click” chemistry. All the polymers were well characterized and soluble in common solvents. By the application of the concept of “suitable isolation group”, the macroscopic nonlinear optical (NLO) properties of the polymers could be boosted to as large as three times that of the polymer without isolation moieties. Also, all the polymers were thermally stable, and demonstrated good procesability, coupled with improved optical transparency. Thus, they are good candidates for the practical applications as new photonic materials.
A new kind of chiral‐dendronized binaphthyl‐containing polyfluorene derivatives has been synthesized through “click chemistry” efficiently. The resulting copolymers exhibited desirable properties, such as excellent solubility, good thermal stability, and considerably high molecular weights. The photophysical properties of the copolymers were investigated in details, and the results indicated that the combination of chiral binaphthyl unit and bulky dendron could effectively suppress intermolecular packing and aggregation. In addition, the investigation of circular dichroism behavior of these chiral‐dendronized copolymers showed a strong Cotton effect at long wavelength (373–379 nm), indicating that the chirality of the binaphthyl units was transferred to the whole polyfluorene backbone.
Metallo‐supramolecular chemistry offers possibilities for the construction of stimuli‐responsive polymeric materials where the environment can have a large impact on the reversibility and strength of interactions between the individual components. The potential of manipulating the strength of the intermolecular non‐covalent bonds can result in impressive modifications of the metallo‐supramolecular structure and, subsequently, produces changes in the properties of the designed material. The present feature article provides an overview on recent developments in the field of metallo‐polymerization of chelating terpyridyl and analogues ligands. Synthetic strategies are described followed by a discussion regarding the characterization and the application of the reviewed metallo‐supramolecular structures, mainly based on terpyridines.
Au nanoparticles (NPs) and polymer composite particles with phase‐separation structures were prepared based on phase separation structures. Au NPs were successfully synthesized in amphiphilic block‐copolymer micelles, and then composite particles were formed by a simple solvent evaporation process from Au NPs and polymer solution. The phase separated structures (Janus and Core‐shell) were controlled by changing the combination of polymers having differing hydrophobicity.
This communication reports a strategy for scale‐up of an in situ polymerization technique for polyolefin‐based nanocomposites preparation, taking layered silicate (clay) and multi‐walled carbon nanotubes (MWCNTs) as examples of nanofillers. The strategy is realized by transforming the nanofillers into granular “nanosupports” for Ziegler‐Natta catalysts. With a catalyst to polymer replication effect on particle morphology, the in situ prepared nanocomposites are of controlled granular particle morphology. With the polymer particle morphology controlled, the in situ polymerization technique becomes suitable for industrial olefin polymerization processes for mass production of polyolefin nanocomposites.
PS grafted silica nanoparticles have been prepared by a tandem process that simultaneously employs RAFT polymerization and click chemistry. In a single pot procedure, azide‐modified silica, an alkyne functionalized RAFT agent and styrene are combined to produce the desired product. As deduced by thermal gravimetric and elemental analysis, the grafting density of PS on the silica in the tandem process is intermediate between analogous “grafting to” and “grafting from” techniques for preparing PS brushes on silica. Relative rates of RAFT polymerization and click reaction can be altered to control grafting density.
Two new “H” type of indole‐based chromophores were designed and successfully introduced to the polymeric system, the resultant polymers demonstrated enhanced NLO effects, good processability, thermal stability and nearly excellent transparency, indicating the advantages of “H” type chromophore moieties. And they could be promising candidates for the practical applications as new photonic materials.
A novel heterogeneous copper(I) catalyst system, which is based on readily available poly(ethyleneimine), has been used as a recyclable catalyst for Cu(I) catalyzed “click” 1,3 dipolar cycloaddition reactions of azides and alkynes in organic media. Branched poly(ethyleneimine) was first methylated and then cross‐linked with 1,9‐dibromononane. Subsequently, after the immobilization of Cu(I)Br, this system was applied for heterogeneous copper catalyzed click chemistry of a few model reagents and polymeric compounds.
One‐dimensional methyl orange fibrils can be easily prepared. They are stable in acidic aqueous solutions and soluble in neutral water. When used to synthesize conducting polymer microtubules, the fibrils act as “hard templates” formally but as “soft templates” effectively. Microtubular structures of polypyrrole, polyaniline, and poly(3,4‐ethylenedioxythiophene) have been achieved successfully via such water‐soluble versatile templates.
The amphiphilic PEG1500‐b‐EM AP‐b‐PEG1500 (EM PAP) triblock copolymer of poly(ethylene glycol) (PEG) and emeraldine aniline‐pentamer (EM AP) in its concentrated solution can self‐assemble into a special shape like “sandglass”, as observed by transmission electron microscopy (TEM), field emission scanning electron microscopy (ESEM) and atomic force microscopy (AFM). This “sandglass”‐shaped assembly is composed of several “rods” aggregated in the middle, with every “rod” being about 8 µm in length and 300 nm in diameter. We conclude that the special “sandglass”‐shaped assembly may come into being because of the inducement effect of the crystallization of EM AP segments, by studying electron diffraction (ED) results and wide‐angle X‐ray diffusion (WAXD) characterization of the EM PAP triblock copolymer.
