A comprehensive kinetic model is developed for a semi‐interpenetrating polymer network (SIPN) process, which involves simultaneous crosslinking, grafting, and degradation. Computational expense has been reduced considerably through a new component decomposition strategy, where a continuous variable approximation and a fixed pivot technique are applied for modeling each component. The inter‐polymer formulation is then reconstructed by a statistical approach. Based on the kinetic parameters obtained from the literature and a series of experiments, the model provides consistent agreement for gel fraction, joint molecular weight distribution (MWD) and polymer composition predicted in the studied cases, showing promising capability for the SIPN industrial application as well as for other polymer composite systems.
Casting a photopolymer solution to form a film, followed by imagewise photoirradiation and subsequent wet development, leads to photolithography. Whereas the wet development is achievable with aqueous alkali, the emission of an organic solvent as a volatile organic compound (VOC) is usually inevitable during the film casting because ingredients of common photopolymers are insoluble in water. We show here a prototype of water‐borne photopolymers dispersed with milled nanoparticles of poorly water‐soluble photoacid generators (PAGs), which undergo solid‐state photolysis to liberate a photoacid to make a poly(vinyl alcohol) film insoluble in water with the aid of an acid‐sensitive crosslinking reagent. The photolysis of onium‐type PAGs is sensitized in the solid state simply by comilling with water‐insoluble sensitizers to extend spectral sensitivity of this kind of photopolymers. Fluorescence quenching measurements revealed that the solid‐state sensitization occurs through exciton migration in sensitizer particles followed by electron transfer to PAG particles.
Near‐infrared (NIR) polymer light‐emitting diodes (PLEDs) based on a fluorene–dioctyloxyphenylene wide‐gap host material copolymerized with a low‐gap emitter are presented. Various loadings (1, 2.5, 10, 20 mol%) of the low‐gap emitter are studied, with higher loadings leading to decreased efficiencies likely due to aggregation effects. While the 10 mol% loading resulted in almost pure NIR emission (>99.6%), the 1 mol% loading yielded optimum device performance, which is among the best reported to date for a unblended single‐layer pure polymer emitter, with an external quantum efficiencies of 0.04% emitting at 909 nm. The high spectral purity of the PLEDs combined with their performance support the methodology of copolymerization as an effective strategy for developing NIR PLEDs.
Well‐defined silica composite nanofibers are generated in a silicification process of self‐assembled poly(ethylene oxide)‐peptide nanotapes. Inspired by biological silica morphogenesis processes the nanotapes exhibit strong binding capabilities for silicic acid. Thus, pre‐hydrolyzed tetramethoxysilane could be used as silica precursor. Very low concentrations (270 µM) and short contact times (10 s) are sufficient to form effectively integrated nano‐composite tapes.
Novel water‐developable negative resists were designed to induce both crosslinking and polarity change upon exposure and bake. The matrix polymers were synthesized by copolymerization of glyceryl methacrylate and methacrolein. The acid‐catalyzed acetalization of the polymer induced crosslinking, polarity change, and an increase in dry‐etch resistance. The resist formulated with this polymer and cast in a water/ethanol mixture showed 0.7 μm line and space patterns using a mercury–xenon lamp in a contact printing mode and pure water as a developer.
The acid‐catalyzed acetalization of poly(GMA‐co‐MA) to form the water‐insoluble acetal. 相似文献
Summary: We have successfully constructed a redox‐responsible hydrogel system by combination of β‐cyclodextrin (β‐CD), dodecyl‐modified poly(acrylic acid) [p(AA/C12)], and a redox‐responsive guest, ferrocenecarboxylic acid (FCA). In the reduced state of FCA, the ternary mixture exhibited a gel‐like behavior, whereas, in its oxidized state, the mixture exhibited a sol behavior.
Conceptual illustration for the redox‐responsive hydrogel system. 相似文献
Reactions between the ethylene groups in the backbone of conjugated polymers under UV illumination and heat treatment result in the cross‐linking of the main polymer chains. The cross‐linking leads to two simultaneous results in the polymer: excellent solvent resistance and increased bandgap. Using this reaction, three‐color polymer light‐emitting diodes (PLEDs) with a multi‐layer structure can be easily realized by a dry photo‐pattern in an active‐gas‐free environment. Multi‐layer blue devices with dramatically enhanced efficiency can also be achieved conveniently.
Hole‐transporting polymers based on polyethene‐triphenylamine derivatives are investigated with respect to their UV/Vis spectra. Two substituents, N‐phenyl‐1‐naphthylamine and carbazole, are examined as their respective polymer light‐emitting diodes (PLEDs) show very different luminous efficiencies. In order to identify the origin of these phenomena electronic structure calculations based on TD‐DFT were performed using monomer models of the hole‐transporting polymers. In experiment these hole‐transporting polymers show very specific differences in their absorption and emission (fluorescence and phosphorescence) spectra. The analysis of the simulated absorption and emission spectra, the MOs as well as the ground and excited state geometries give explanations for the different optical performances of the corresponding PLEDs.
Dendrimer‐protected gold nanoparticles have been facilely obtained by heating an aqueous solution containing third‐generation poly(propyleneimine) dendrimers and HAuCl4 without the additional step of introducing other reducing agents. Transmission electron microscopy (TEM) and UV‐vis data indicate the size, the nucleation, and growth kinetics of gold nanoparticles thus formed, which can be tuned by changing the initial molar ratio of dendrimer to gold.
The formation of dendrimer–gold nanoparticles by the heat treatment of an aqueous solution containing third‐generation poly(propyleneimine) dendrimers and HAuCl4. 相似文献
Polycondensation of 1‐(2‐pyrimidinyl)pyrrole with 2,7‐dibromo‐9,9‐dioctylfluorene via Ru‐catalyzed direct arylation gives the corresponding conjugated polymer with a molecular weight of 19 800 in 86% yield. The introduction of directing group, 2‐pyrimidinyl substituent, into the pyrrole monomer induces ortho‐metalation and provides the site‐selective direct arylation polycondensation at the α‐position of pyrrole unit without the protection of β‐position. The removal of 2‐pyrimidinyl substituent on the pyrrole unit proceeds efficiently and results in the enhancement of coplanarity along the main chain of the polymer.
Low‐cost, responsive poly(N‐isopropylacrylamide)/polystyrene composite films were prepared by a facile electrospinning technique. The surface structures and wettabilities of the composite films are tunable by simply controlling the concentration of polymer. With a proper proportion of each polymer, the wettability of the surface can be switched between superhydrophilicity and superhydrophobicity when the temperature is changed from 20 °C to 50 °C. The combination of a stimuli‐responsive polymer with micro/nanostructures on the surface of the composite film contributes to this unique surface property.
Photo‐induced reversibility as a tool for self‐healing: a reversible photo‐induced dendritic macromonomer was synthesized and proven to form networks with different features depending on the crosslinking conditions. While networks formed from aqueous systems exhibited a reversible change in their crosslinking degree, networks generated in bulk underwent fully reversibility. The latter was then exploited for generating self‐healing materials by means of a photo‐induced treatment.
It is demonstrated that an optically transparent and electrically conductive polyethylene oxide (PEO) film is fabricated by the introduction of individualized single‐walled carbon nanotubes (SWNTs). The incorporated SWNTs in the PEO film sustain their intrinsic electronic and optical properties and, in addition, the intrinsic properties of the polymer matrix are retained. The individualized SWNTs with smaller diameter provide high transmittance as well as good electrical conductivity in PEO films.
Highly dispersed ZnO nanoparticles with variable particle sizes were successfully prepared within an amphiphilic hyperbranched polyetherpolyol matrix via decomposition of an organometallic precursor in the presence of air leading to stable nanocomposites. The high degree of stabilization during and after the synthesis by the polymer permits control over the nanoparticle size and therefore, due to the quantum‐size‐effect, the particle properties. Furthermore, these polymer‐inorganic nanocomposites can easily be dispersed in apolar solvents to yield highly transparent, stable solutions.
Blue emission of oxygen‐doped tertiary amine (triethylamine), a key unit of fluorescent poly(amido amine) dendrimer, was demonstrated. It was found that the fluorescence intensity could be further enhanced if the tertiary amines locate densely in the dendrimer interior as the branching sites. Moreover, a solvatochromic phenol blue, instead of oxygen, is able to induce the blue fluorescence of the tertiary amino‐branching sites based on a guaranteed host‐guest complexation of phenol blue molecules and dendrimer interior.
The single‐polymer form factor is determined for branched polymers using a scaling argument in order to recover the low‐Q Porod exponent characteristic of the overall structure. The high‐Q Porod exponent characterizes the local branching structure. An alternative approach based on a high‐Q expansion contains information about functionality, branch length and branch content. The specific case of a starburst dendrimer for which the form factor is known is discussed. The model predictions are compared to small‐angle neutron scattering data from a dilute solution of dendrimer in D2O.
