Kaiser's “abt” concept rests on the experimental establishment of a linear relation between band width at half height, b0.5, and capacity ratio, k, according to His column specification quantity, hreal, is dependent on the square of the slope a, obtained from a linear regression analysis based on this relation. It is shown in the present paper that an improvement of the experimental conditions leading to a lower extra-column contribution to band broadening, b, introduces a tendency towards a negative curvature in the plot at low k values. The mean slope increases, and an uncritical linear regression would yield an hreal-value which is higher than before and which would be in the opposite direction to the requirements of a reliable column specification. Generally the linear regression analysis has to be moved to higher k regions in cases of curvature, especially as it is also shown that hreal is an estimation of the traditional HETP value, H∞, that would be obtained when k approaches infinity. This theoretically expected relation is a strong motivation for the use of hreal as a column specification, since the b0.5-value associated with H∞ is expected to be practically independent of b. 相似文献
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.
A novel type of multivalent and highly specific fluorescent hyperbranched glycopolymers h‐P(GalEA‐co‐VBPT‐co‐BYMA) (hPGVB) is designed and prepared successfully via a facile “bottom‐up” strategy. The acetylated hPGVB is prepared by one‐pot reversible addition‐fragmentation chain transfer (RAFT) copolymerization of acrylate‐type galactose monomers AcGalEA and methacrylate‐type fluorescent monomers BYMA in presence of an inimer‐type RAFT chain transfer agent. After deacetylation, the resulting amphiphilic hPGVB can self‐assemble into stable nanoparticles in aqueous media, showing strong green fluorescence with relative high quantum yields and good photostability. The cell viability study indicates the excellent biocompatibility of the hPGVB fluorescent nanoparticles (FNPs) against HepG2 and NIH3T3 cells. More importantly, comparing with the galactose‐free fluorescent hyperbranched polymers h‐P(OEGMA‐co‐VBPT‐co‐BYMA), hPEVB FNPs can be selectively internalized by asialoglycoprotein (ASGP) receptor‐rich HepG2 cells, indicating their potential application in the bioimaging fields. 相似文献
Mechano‐activated chemistry is a powerful tool for remodeling of synthetic polymeric materials, however, few reactions are currently available. Here we show that using piezochemical reduction of a CuII‐based pre‐catalyst, a step‐growth polymerization occurs via the copper catalyzed azide–alkyne cycloaddition (CuAAC) reaction to form a linear polytriazole. Furthermore, we show that a linear polymer can be crosslinked mechanochemically using the same chemistry to form a solid organogel. We envision that this chemistry can be used to harness mechanical energy for constructive purposes in polymeric materials. 相似文献
We have synthesized a “universal ligand” incorporating a phosphonate surface anchor and a terminal alkyne moiety which binds to TiO2 nanoparticles and exhibits excellent dispersity in organic solvents. The alkyne functionality permits attachment of azide terminated polymer shells using “click” chemistry. Thus TiO2 core nanoparticles have been encapsulated with both polystyrene and poly(t‐butyl acrylate) shells. The TiO2‐poly(t‐butyl acrylate) core shell nanoparticles are amenable to further chemical transformation into TiO2‐poly(acrylic acid) nanoparticles through ester hydrolysis. These TiO2‐polyacrylic acid nanoparticles are dispersible in aqueous solution. The resulting core‐shell nanoparticles have been incorporated as high K dielectric films in capacitor and organic thin film transistor devices and are promising new materials for flexible electronics applications.
The choice of electrode material and surface preparation method are usually dictated by the suitability of the electrode to observe an electrochemical parameter, such as heterogeneous electron transfer rate, surface coverage, or redox potential. Thus, the glassy carbon (GC) and platinum (Pt) electrodes were modified with multiwalled carbon nanotubes (MWCNT) by direct “casting” modification using nine different aliquots of solvents. After drying at room temperature, the modified electrode showed distinct redox peaks corresponding to ferrocyanide oxidation/reduction. Using chemometrics, the cyclic voltammograms with higher current intensity were obtained for those in which ethanol, water and acetone as dispersing agents were used for GCE and dimethylformamide, water and acetone for Pt electrode modification. 相似文献