By Monte Carlo simulations we provide insight into the isolated single‐ and double‐tethered (ST and DT) polymer chain attached to an impenetrable surface to elucidate open theoretical questions and guide future experiments investigating the impact of tethering on the genome packaging by concurrent visualisation of multiple loci along the chromosome(s). In the models, either one or both ends (at a grafting distance d) are fixed or the ST and DT chain are “annealed” by permitting the anchor(s) to diffuse laterally along the surface. We analyse chain self‐entanglement, intrachain segment correlations, the relationship between mean square physical distance and corresponding contour length and provide the first report on the diffusion behaviour.
We report for the first time the preparation of single polypyrrole (PPy) molecule chains using a “metal‐organic framework” with 1 nm channels as a template. The obtained one‐dimensional (1‐D) PPy has highly structure order and excellent conductivity, which has improved by as much as five orders of magnitude in comparison with that of 2‐D PPy.
Anionic conjugated polymer (PFP‐SO) was assembled with a novel enzymatic substrate 6‐O‐modified PNP‐β‐galactoside ( 1 ) for sensitive multiplex enzyme detections. The PFP‐SO/ 1 /lipase/β‐galactosidase system has two chemical input signals which are Input 1 (lipase) and Input 2 (β‐galactosidase), and output optical signals such as fluorescence emission at 416 nm or 450 nm. Four types of logic gates, including YES, INH, NAND and AND, were successfully constructed and utilized for multiplex detections of lipase and β‐galactosidase in one tube.
We report syntheses of phenylene‐, biphenylene‐, and terphenylene‐layered polymers with a xanthene scaffold by the modified Suzuki‐Miyaura coupling reaction. Their optical properties were studied in detail. The polymer end‐capped by nitrobenzene units, which act as fluorescence quenchers, exhibited the photo‐excited energy transfer from the layered oligophenylenes to the terminal units.
Macroporous temperature‐sensitive poly(N‐isopropylacrylamide) (PNIPA) hydrogels were prepared by a novel phase‐separation technique to improve the response properties. In comparison with a conventional PNIPA hydrogel prepared in water, these macroporous hydrogels, prepared by polymerization in aqueous sucrose solutions, have higher swelling ratios at temperatures below the lower critical solution temperature and exhibit much faster response rates to temperature changes.
Scanning electron microscopy image of the surface of a PNIPA hydrogel, prepared in 1.50 M aqueous sucrose solution. 相似文献
Rapidly shrinking poly(N‐isopropyl acrylamide) (PNIPAM) hydrogels are prepared by crosslinking with self‐assembled nanogels that consist of cholesteryl‐ and methacryloyl‐substituted pullulan (CHPMA). The CHPMA nanogel (Rh = 26.4 nm) was used as a crosslinker for a hydrophilic nanodomain. Transmission electron microscopy images of the nanogel‐crosslinked PNIPAM hydrogel reveal a well‐defined nanoporous structure. The nanogel‐crosslinked PNIPAM hydrogel shows rapid shrinking based on its structure. The shrinking half‐time was ≈2 min, which is about 3 400 times faster than that of a PNIPAM hydrogel crosslinked by methylene(bisacrylamide).
A dramatic increase in the photostability of a blue‐light‐emitting polymer, poly(9,9‐dioctylfluorene), was achieved by the addition of 5–10 nm gold nanoparticles. The optical absorption band of the gold nanoparticles was tuned to resonate the triplet exciton ground state bandgap energy of the polymer. Photo‐oxidation rate of poly(9,9‐dioctylfluorene) was effectively reduced by doping the polymer with very small amounts (≈10−6–10−5 volume fraction) of the gold nanoparticles.
Retarded photo‐oxidation in PDOF nanocomposite films with various doped gold nanoparticles. 相似文献
Large scale of well‐ordered macroporous π‐conjugated polymer monoliths have been successfully prepared through a new approach using micrometer‐sized naphthalene crystals as templates. The macroporous monoliths of poly(p‐phenylenevinylene) (PPV) and poly(p‐phenyleneethynylene) (PPE) grew along the unidirectional freezing direction inside the template naphthalene crystals which lead to the formation of controlling morphologies and homogeneous diameters. The polymer monoliths show straight and lamella macroporous structures. The diameters of pores and the thickness of pore walls can be controlled by tuning the freezing temperature.
Blue‐light‐emitting 2,7‐carbazole‐based conjugated copolymers have been prepared by Yamamoto or Suzuki cross‐coupling reactions. By introducing highly substituted aromatic comonomers, fully soluble high‐molecular‐weight copolymers have been obtained. Moreover, these amorphous polymeric materials exhibit good thermal stability and interesting redox properties. All these features make these new conjugated polymers highly promising for the development of single‐polymer‐layer blue‐light‐emitting diodes.
A novel approach is employed to produce core–corona nanospheres, which introduces a stereoregular hydrophilic part to an amphiphilic block copolymer. The resultant morphology is reported using isotactic‐poly(methacrylic acid)‐block‐poly(butyl acrylate). Infrared spectroscopy revealed a supramolecular interaction, and X ray diffraction revealed the crystallization of the outer isotactic‐poly(methacrylic acid) part. The nanostructure, which looks like a nanosized ‘grape’, was formed when nanospheres and nanofibers coexisted simultaneously and partially fused.
Summary: This study aims at developing a highly electronic conductive microporous structure from thermoplastic polymers filled with carbon black (CB) and graphite (GR). The matrix was a low viscosity poly(propylene) (PP) and the conductive additives were composed of high specific surface area CB and synthetic flake GR. Conductive blends were first developed using a corotating twin‐screw extruder. Rheological properties and conductivities of these blends were then characterized as a function of blend composition. Blends that show the best compromise between electronic conductivity and processability were subsequently extruded through a sheet die to obtain films of around 500 µm in thickness. These films were then stretched in two successive steps under controlled temperature and stretching rate to generate a film of controlled microporous structure.
TEM of film made from a 50 wt.‐% PP/25 wt.‐% CB/25 wt.‐% GR blend after stretching. 相似文献
Hydrogen‐bonded supramolecular copolymers were easily prepared by mixing cyclohexanetricarboxamides with three ( 1 ) and six ( 2 ) alkylsilyl groups, and supramolecular fibers were fabricated. When the composition of 1 and 2 was at or close to equimolarity, the supramolecular copolymer chain was found to have an alternating sequence. This was attributed to the fact that the steric factor of the alkylsilyl side chains effectively controls the unit sequence of the supramolecular polymer chain.
A generalized silica coating scheme is used to functionalize and protect sub‐micron and micron size dicyclopentadiene monomer‐filled capsules and polymer‐protected Grubbs' catalyst particles. These capsules and particles are used for self‐healing of microscale damage in an epoxy‐based polymer. The silica layer both protects the capsules and particles, and limits their aggregation when added to an epoxy matrix, enabling the capsules and particles to be dispersed at high concentrations with little loss of reactivity.
Supramolecular self‐assembly of block copolymers in aqueous solution has received ever‐increasing interest over the past few decades due to diverse biological and technological applications in drug delivery, imaging, sensing and catalysis. In addition to relative block lengths, molecular weights and solution conditions, chain architectures of block copolymers can also dramatically affect their self‐assembling properties in selective solvents. This feature article mainly focuses on recent developments in the field of supramolecular self‐assembly of amphiphilic and double hydrophilic block copolymers (DHBCs) possessing nonlinear chain topologies, including miktoarm star polymers, dendritic–linear block copolymers, cyclic block copolymers and comb‐shaped copolymer brushes.
ATRP of 2‐(N,N‐dimethylamino)ethyl acrylate (DMAEA) was investigated using CuBr or CuCl with different multidentate ligands. The catalyst was found active for DMAEA polymerization when ligated with tris[2‐(N,N‐dimethylamino)ethyl]amine. Good control over molecular weight was achieved, but quaternization of the terminal monomeric/polymeric tertiary amine by the C Br group of polyDMAEA caused chain termination. Using a chloride‐based system helped to suppress chain termination. Amphiphilic poly(methyl acrylate)‐block‐polyDMAEA was synthesized using polyMA as a macroinitiator.
Molecular weights and polydispersities of polyDMAEA versus DMAEA conversion for different catalyst systems. 相似文献
A novel self‐oscillating gel actuator with gradient structure, which generates a pendulum motion by fixing one edge of the gel without external stimuli was achieved. The gel was synthesized by copolymerizing the ruthenium catalyst for the Belousov‐Zhabotinsky reaction with N‐isopropylacrylamide and 2‐acrylamido‐2‐methylpropane sulfonic acid. Furthermore, we clarified that the period and amplitude for the self‐oscillating behavior of the gel actuator are controllable by changing the composition, temperature, and size of the gel. The maximum amplitude of the novel gel actuator is about a 100 times larger than that of the conventional self‐oscillating gel system.
