In this paper, the hydrogel is created with oriented structure by addition of very little amount of dopant, filamentous actin (F‐actin), which is 1/50 000 of lower critical concentration for nematic phase in F‐actin aqueous solution. The orientation mechanism of polymer network differs depending on the concentration of F‐actin. Furthermore, it is first exhibited that the role of polyelectrolyte for the emergence of anisotropy of gel is differed depending on its concentration by using digestion method to F‐actins, experimentally.
The structure, molecular weight, and molecular weight distribution (MWD) of polyisoprene fractions, which were obtained during the fraction of polyisoprene with broad MWD (Mw/Mn = 25.6) synthesized with tBuCl/TiCl4 initiating system have been investigated. It is established that chain transfer to polymer leading to branched macromolecules is responsible for the formation of polyisoprene with broad MWD and reduced unsaturation. It is shown for the first time that unsaturation decreased while the content of head and end groups in a single macromolecule increased with increasing molecular weight of polyisoprene fraction. The unsaturated part of the polymer chain consists of presumably trans‐1,4‐units independently of the molecular weight of polyisoprene fraction.
Copolymerization of ethylene with 4‐penten‐1‐ol (4P1O) is conducted by using a half‐titanocene catalyst. The incorporation of 4P1O is high as approximately 10 mol%. The assignments of the 13C NMR spectrum and the analysis of the sequence distribution show the existence of not only the alternative structure but also the repeated 4P1O units. The product of the reactive ratios is calculated as ca. 2.
Condensation reaction of asymmetric triamine (spermidine) with guanidine hydrochloride provides a phantom structure with selective formation of rings in the repeat unit. The intermolecular condensation between amine and guanidine hydrochloride can provide either a linear structure or six‐ or seven‐membered rings in the repeat unit by elimination of one or three molecules of ammonia, respectively, per repeat unit. The preference of formation of rings and mechanistic aspects are studied by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, 1D, 2D NMR, and quantum chemical calculations.
Whether manganese ion can induce DNA condensation at room temperature has not been clarified. In this study, direct evidence of Mn2+ ion‐induced DNA condensation is provided by single‐molecule measurements and atomic force microscopy characterization. It is shown that elevated temperature is not a requirement to induce DNA condensation, but helps to promote the process at the ensemble level. The finding suggests the failure of the Manning theory in explaining Mn2+‐DNA interactions and refreshes the view that divalent metal ions cannot cause DNA condensation. The localized binding of Mn2+ on DNA is believed to induce condensation.
This article summarizes the recent advances of benzothiadiazole (BT)‐containing conjugated polyelectrolytes (CPEs) for biological sensing and imaging. After a brief introduction of the molecular design principles, the application of linear BT‐containing CPEs as multicolor or light‐up probes for visual sensing of biomolecules is reviewed. Then, linear, grafted, and hyperbranched BT‐containing CPEs that can self‐assemble into nanoparticles or have intrinsic 3D structures for in vitro and in vivo imaging are summarized. The future outlook of BT‐containing CPEs for biomedical applications is also discussed at the end.
The polycycloaddition of azomethine ylides to dipolarophiles is described for the first time. Use of (cis,cis)‐bis‐aziridines as a source of azomethine ylides allows selective polyaddition to be realized, which leads to oligomers exclusively with trans‐substituted pyrrolidine rings and modest molecular weights (ca. 5–10 kDa). The fluorescent, electrochemical, electrochromic, and non‐linear optical properties of the main‐chain free‐base porphyrin oligomer, synthesized by the developed procedure, are studied. An enhancement of the optical power limiting effect in a porphyrin oligomer solution is registered against that of the monomer.
A new method is presented for the extraction of single‐chain form factors and interchain interference functions from a range of small‐angle neutron scattering (SANS) experiments on bimodal homopolymer blends. The method requires a minimum of three blends, made up of hydrogenated and deuterated components with matched degree of polymerization at two different chain lengths, but with carefully varying deuteration levels. The method is validated through an experimental study on polystyrene homopolymer bimodal blends with . By fitting Debye functions to the structure factors, it is shown that there is good agreement between the molar mass of the components obtained from SANS and from chromatography. The extraction method also enables, for the first time, interchain scattering functions to be produced for scattering between chains of different lengths.
P3HT (poly (3‐hexylthiophene)) has been widely used as a donor in the active layer in organic photovoltaic devices. Although moderately high‐power conversion efficiencies have been achieved with P3HT‐based devices, structural details, such as the orientation of polymer units and the extent of H‐ and J‐aggregation are not yet fully understood; and different measures have been taken to control the ordering in the material. One such measure, which has been exploited, is to apply an electric field from a Van de Graaff generator. Fluorescence (to measure anisotropy instead of polarization, which is more commonly measured) and Raman spectroscopy are used to characterize the order of P3HT molecules in thin films resulting from the field. Preferential orientations of the units in a thin film are determined, consistent with observed hole mobility in thin‐film transistors, and it is observed that the apparent H‐coupling strength changes when the films are exposed to oriented electrical fields during drying.
The calorimetric trace of polymer spheres shows an increase of the glass‐transition temperature (Tg), with respect to its bulk value. This increase is evaluated by means of an entropy model, where the 3D confinement leads to a limiting number of repeating polymer units in the sphere, and thus to a reduction of the possible configuration states of the polymer chains. This is ultimately related to variations in the bulk value of the Tg. Also, the way the polymer nature affects how confinement takes place and how restrictions imposed affect the way a polymer forms cooperative rearranging regions at Tg are presented.
The inner walls of thin glass capillaries are coated with a reactive precursor coating that can be converted into different temperature‐ and light‐responsive coatings. The switching range of wettability can be determined by measuring the meniscus height of water inside these capillaries at different temperatures and upon UV‐light irradiation. In comparison with the sessile drop measurement, very accurate equilibrium contact angles are obtained by this method.
The pulsed laser polymerization–high termination rate limit–size‐exclusion chromatography (PLP–HTRL–SEC) technique is used to estimate the mode of termination (δ) for n‐butyl methacrylate (n‐BMA) polymerization at 30 °C. It is found that molecular mass distributions measured in these experiments are influenced by an unknown side reaction such as retardation or chain transfer that results in a marked decrease of intensity of the PLP peak. A new approach is developed to evaluate δ, with numerical experiments used to demonstrate the robustness of the methodology in the presence of retardation or chain transfer to agent. Application to the experimental n‐BMA polymerization at 30 °C leads to an estimate for δ of 0.60 ± 0.03.
In the current investigation, nanocomposites containing a β‐nucleated poly(propylene‐co‐ethylene) (PPR) matrix filled with untreated (SiO2) and methacrylate‐modified silica nanoparticles (SiO2‐MAA) are prepared. Transmission electron microscopy (TEM) reveals the improvement in the quality of dispersion due to the surface modification of the nanoparticles. Also, from differential scanning calorimetry (DSC) and X‐ray diffraction (XRD), it is found that the β‐nucleating agent and silica nanoparticles work synergistically in order to increase the relative β‐content in the nanocomposite samples. The thermal stability of each samples is evaluated by means of thermogravimetric analysis (TGA) and the enhancement of the thermal stability of the nanocomposites is attributed to the nanoconfinement of the macromolecular chains caused by the presence of the fillers.
A novel symmetrical selenium‐based reversible addition‐fragmentation chain transfer (RAFT) agent, Se,Se’‐dibenzyl carbonodiselenothioate (Se‐RAFT), is synthesized and used in the RAFT polymerization of styrene. The results obtained show that the Se‐RAFT agent is involved in the polymerization of styrene, as evidenced by narrow molar‐mass distributions (/ < 1.6) and the incorporation of the Se‐RAFT moiety into the resultant polymer. The latter is confirmed by aminolysis, NMR spectroscopy, size‐exclusion chromatography (SEC) and UV spectroscopy. This work provides detailed insight into the Se‐RAFT polymerization mechanism. The Se‐RAFT agent is unique in that the stabilizing and leaving groups are identical.
The preparation of thermoresponsive fibers made from a crosslinked liquid‐crystalline (LC) side‐chain polymer is presented. For this, an LC polyacrylate with side‐on attached mesogens and crosslinkable units is synthesized and processed in solution in a microfluidic co‐flowing device. Due to the high viscosity of the polymer and the reduced interfacial tension between the dispersed polymer solution and the immiscible ambient fluid, it becomes possible to produce and stabilize a liquid jet against its breaking into droplets, even at low shear rates. The polymer jet is finally stabilized in the capillary by UV‐initiated photopolymerization leading to well‐oriented, crosslinked LC fibers. If the crosslinking density in these fibers is moderate (LCEs), contractions of several 100% can be observed at the nematic–isotropic phase transition.
A series of brominated polystyrenes (BPSs) are readily synthesized and blended as polymer dopants with the p‐type semiconducting polymer, poly(3‐hexylthiophene) (P3HT), to improve theirelectrical performance. The obtained P3HT/BPS blend films exhibit increased carrier concentration resulting from doping of P3HT by BPS, which leads to excellent electrical performance, including enhanced hole mobility and conductivity, and the conductivity or mobility increases with the bromination degree of BPS. Compared with conventional small molecular dopants, the polymer dopant, BPS, shows not only excellent doping stability, but also good solution processibility, which makes it a promising materials for fabrication of low cost, flexible, transparent, and high performance solution processable organic electronic devices.
A novel polymer membrane ( TPP‐M ) with strong light harvesting ability within the entire visible‐ light spectrum has been prepared, in which the meso‐tetrakis(4‐cyanophenyl) porphyrin ( TPP‐1 ) as a functional unit is highly crosslinked through an aromatic nitrile trimerization reaction. The designed triazine framework controls the size of the π‐conjugation and retains the excellent photophysical properties of monomeric porphyrin, such as strong absorption and high singlet oxygen quantum yield. Due to these excellent photophysical properties and low solubility in common organic solvents, polyporphyrin membranes, as efficient singlet oxygen (1O2) sensitizers, could be easily recycled and reused for the photo‐oxidation of 1,5‐dihydroxynaphthalene (DHN).
A size exclusion chromatography (SEC)‐gradient method is developed allowing poly(n‐butyl acrylate‐stat‐acrylic acid)s to be separated with respect to content of acrylic acid over the complete composition range. After setting up the chromatographic method, samples that, according to the amounts of charged monomers, are expected to have identical chemical composition are compared. The chromatograms reveal differences in elution volume, which, by 1H NMR spectroscopy, can be partially traced back to differences in polymer composition. In addition, samples of similar compositions prepared in different solvents exhibit differences in chemical composition distribution.
Multiple suspension particles — a new morphology of polymer particles — are generated on the verge of colloidal stability in the course of redox‐initiated aqueous heterophase copolymerization. These particles consist of block copolymers which are arranged in the form of a micrometer‐sized poly(N‐isopropylacrylamide) physical network as scaffold containing nanometer‐sized particles of hydrophobic polymers covalently attached.
In this study, in situ small‐angle X‐ray scattering (SAXS), in situ Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM) are used to monitor the formation of ordered mesophases in cured mixtures of phenolic resin and the diblock copolymer poly(ethylene oxide‐block‐ε‐caprolactone) (PEO‐b‐PCL). SAXS and TEM analyses reveal that the mesophase of the phenolic/PEO‐b‐PCL mixture transforms sequentially from disordered to short‐range‐ordered to hexagonal‐cylindrical to gyroidal during the curing process when using hexamethylenetetramine (HMTA) as a cross‐linking agent, indicating that a mechanism involving reaction‐induced microphase separation controls the self‐assembly of the phenolic resin. In situ SAXS is also used to observe the fabrication of mesoporous phenolic resins during subsequent calcination processes.
下载免费PDF全文