A ‘grafting‐from’ approach to synthesize microparticle‐supported conjugated polyelectrolyte brushes is presented. Poly(3‐bromohexylthiophene) is selectively grown from monodisperse organosilica microparticles by surface‐initiated Kumada catalyst‐transfer polycondensation (SI‐KCTP) and then ionizable amino groups are introduced by a two‐step polymer analogous transformation. Optical properties of the resulting microparticle‐supported conjugated polyelectrolyte brushes were found to be dependent on the surrounding chemical environment and thus the particles are promising materials for sensor applications.
The kinetics of microemulsion polymerization depend on the structure of the initial microemulsion and the transport of species between the aqueous domain, the micelles, and the polymer particles. The water solubility of the monomer and the proximity of the initial microemulsion composition to a phase boundary are key considerations for studying microemulsion polymerization kinetics and producing the desired products. Complications frequently arise in the synthesis of copolymers or the incorporation of controlled polymerization mechanisms because of the compartmentalized nature of microemulsion polymerizations.
We describe an enzyme‐responsive polymeric vehicle, which is of great interest in controlled drug delivery, biosensing, and other related areas. The polymer synthesized using lipase as catalyst in DMSO has a favorable molecular structure that is quickly hydrolyzed by lipase in aqueous phase, and allows a fast release of encapsulated molecules.
Furan ring‐functionalized solid surfaces are achieved by the initiated chemical vapor deposition (iCVD) method, a solvent‐free process to form films under mild conditions. The polymerization of furfuryl methacrylate monomer is initiated by a resistively heated filament wire. The functionality of the furan group in the iCVD film enabled Diels–Alder chemistry with 4‐phenyl‐1,2,3‐triazolin‐3,5‐dione (N‐PTD).
A photochemical approach toward the generation of enzyme‐containing redox polymer networks, which are the key material in enzymatic sensors and biofuel cells, is described. The approach is based on the incorporation of photo‐reactive benzophenone groups into the redox polymers. The obtained polymers are then deposited on the surface of glassy carbon electrodes and cross‐linked by illumination with UV light at 365 nm. If this step is done in the presence of the enzyme glucose oxidase, functional electrodes are obtained that yield electrical power upon addition of glucose. This work specifically addresses the question of electrode stability in buffer and demonstrates how slight variations in the chemistry of the redox polymer have a dramatic effect on the electrochemical performance of the electrodes. Different ferrocene‐containing redox polymer networks are synthesized and their properties in physiological buffer are studied.
One of the most important events in free‐radical emulsion polymerization is desorption of radicals from the polymer particles to the aqueous phase. Desorption takes place by diffusion of radicals inside the particle toward the surface and transfer to the aqueous phase. The rate of desorption can be determined theoretically for homogeneous spherical particles. For more complex cases, analytical solutions become difficult or impossible to obtain and a numerical approach is better suited for estimating desorption rate coefficients. In this paper, Brownian dynamics simulation is used for the estimation of desorption rate coefficients in emulsion polymerization systems of increased complexity, in particular for non‐homogeneous polymer particles.
An isotropic melt of a chiral side‐chain polymethacrylate was studied by electric birefringence technique. A phase transition between two different isotropic phases was detected by Kerr effect and confirmed by WAXS measurements. The obtained experimental data can explain the previously reported bistable phase behavior of the polymer, as conventional Sm A phase is formed in slow cooling whereas a TGB‐like, optically isotropic mesophase in fast cooling.
Summary: The evolution of the photoinduced birefringence in thin films of narrow polymer fractions is studied and compared with the behavior of the non‐fractionated polymer. The Δnind value decreases by increasing the degree of polymerization ( ) within the oligomeric range but becomes independent of molecular weight starting from a of ≈70. Thermal pretreatment of the films results in higher photoinduced birefringence. The films show good stability of the photorecording.
Birefringence induced after 10 min, Δnind(600) and its growth rate at the same moment versus molecular weight. 相似文献
Summary: We describe an interesting approach to the fabrication of wettability gradients from hydrophobicity to superhydrophobicity in low‐density polyethylene (LDPE) films by first forming high porosity surfaces and placing the specimens onto linear temperature gradients. While the polymer chosen for the study is non‐polar, its microporous layer provides sufficient superhydrophobicity. Lateral gradient heating of the layer results in partial melting of the polymer and correspondingly decreases porosity thus decreasing hydrophobicity.
A dextran‐based dual‐sensitive polymer is employed to endow gold nanoparticles with stability and pH‐ and temperature‐sensitivity. The dual‐sensitive polymer is prepared by RAFT polymerization of N‐isopropylacrylamide from trithiocarbonate groups linked to dextran and succinoylation of dextran after polymerization. The functionalized nanoparticles show excellent stability under various conditions and can be stored in powder‐form. UV and DLS measurements confirm that the temperature‐induced optical changes and aggregation behaviors of the particles are strongly dependent on pH.
A new π‐conjugated charge‐transfer‐type copolymer of electron‐donating thiophene and electron‐accepting quinoxaline was prepared by organometallic polycondensation. The polymer was soluble in organic solvents such as tetrahydrofuran, and showed a UV‐vis peak at long wavelengths of 598 nm in chloroform and 629 nm in the film. Its film exhibited a χ(3) peak in the resonance region with a χ(3) value comparable to that of regioregular head‐to‐tail poly(3‐hexylthiophene‐2,5‐diyl).
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.
Amphiphilic hybrid π‐conjugated polymers that have polyhedral oligomeric silsesquioxanes on their side chains have been successfully synthesized by the Sonogashira–Hagihara polycondensation reaction. The obtained polymers were studied with ultraviolet‐visible absorption and photoluminescence spectra. In these polymers, the π‐conjugation length was extended along the poly(p‐phenylene‐ethynylene) backbone. Furthermore, the content of the POSS substituents can influence the aggregation behavior of the polymers and subsequent luminescent properties.
This paper describes random branching theory, a model for the solution structure of hyperbranched polymers. In this model, the hyperbranched polymer is assumed to be composed of units whose structure is simpler than the resulting polymer. These simple units can have any structure of chemical functionality, from monomers to linear chains or spherical particles. This paper outlines how this theory is constructed, describes the underlying assumptions and parameters, and summarizes the most basic form. It is shown how variations in the parameters change the behavior of the model, and described how to fit an experimental data series. This demonstrates how the model can be used to fit other data series, and how it can be used as a test for whether a polymer is randomly hyperbranched.
A novel method of macromolecule encapsulation using micron‐sized polymeric shells constructed with a photoactive azobenzene containing polyelectrolyte is discussed. Fluorescently labeled dextran molecules were encapsulated using light to remotely shrink and change the wall permeability of new polymeric hollow shells. We observed that the proportion of shells with dye encapsulated increased along with the duration of irradiation. Electron microscopy imaging illustrated significant changes in the surface roughness of shells after being exposed to light. Finally, this new system was shown to possess a high thermal stability.
A new type of polymeric hybrid coating is created by layer‐by‐layer deposition of polyelectrolyte multilayers (PEM) onto nano‐patterned polymer brushes (NPB). The PEM is a hydrogen‐bonded multilayer consisting of poly(acrylic acid) and poly(acrylamide) and the NPB is derived from a surface reactive rod‐coil block copolymer, polystyrene‐block‐poly[3‐(triethoxysilyl)propylisocyanate]. The thickness of the PEM coating is optimized with respect to the height of the NPB mounds, to yield PEM/NPB hybrid coatings with unique nano‐embossed or nano‐porous structures that can be interchangeable by heating and moisture annealing. The hybrid coating is patternable by the micro‐contact printing method. The results demonstrate that the combination of surface‐bound, hydrophobic NPB layer with hydrophilic PEM films at the nanoscopic level offers a new organic hybrid coating with novel surface properties.
This communication details the successful synthesis of low polydispersity core cross‐linked star (CCS) polymers via DPE‐mediated polymerisation. We demonstrate the ability to produce poly(methyl methacrylate) and poly(acrylonitrile) CCS polymers that are currently inaccessible via the two most common non‐metal‐based controlled radical polymerisation techniques (NMP and RAFT polymerisations).
Summary: Self‐oscillating polymers and nano‐gel particles consisting of N‐isopropylacrylamide and the ruthenium catalyst of the Belousov‐Zhabotinsky reaction have been prepared. In order to clarify the crosslinking effect on the self‐oscillating behavior, the phase transition behaviors were investigated by measuring the transmittance and the fluorescence intensity of the polymer solution and the gel bead suspension. Cooperative effects due to crosslinking will play an important role for the design of nanoactuators.
Chemical structure of poly(NIPAAm‐co‐Ru(bpy)3). 相似文献
Integration of biocompatible silica with a fluorescent polymer (PDDF) and superparamagnetic iron oxide nanoparticles (Fe3O4) to form uniform core–shell nanostructures has the great potential to form particles for use in multimodal bioimaging applications. Core–shell nanoparticles (PDDF/Fe3O4@SiO2) exhibit fluorescent and magnetic properties that are favorable for their use in magnetic separation and guiding applications, as well as optical and magnetic resonance (MR) imaging capabilities. With the biological analysis in an in vitro intracellular permeation and cytotoxicity test, chemical conjugation of the surface using folic acid (FA) molecules can provide the nanoparticles with cell‐targeting properties, localizing the nanoparticles to folate receptors (FRs) on target KB cells that over‐express the FRs.
