The living cationic ring opening polymerization of 2-ethyl-2-oxazoline performed in an ionic liquid under microwave irradiation showed an enhanced polymerization rate in comparison to the reaction in common organic solvents; the ionic liquid was efficiently recovered and reused in new reaction cycles, completely avoiding the use of organic volatile compounds. 相似文献
The influence of Hofmeister salts was investigated on the cloud point of three poly(2‐oxazoline)s, namely poly(2‐ethyl‐2‐oxazoline) [PEtOx], poly(2‐n‐propyl‐2‐oxazoline) [PnPropOx], and poly(2‐isopropyl‐2‐oxazoline) [PiPropOx]. In addition, a comb polymer based on oligo‐2‐ethyl‐2‐oxazoline side chains and a methacrylate backbone (POEtOxMA) was included in this investigation. It was found that the ionic response of the poly(2‐oxazoline)s strongly depends on their hydrophilicity. The comb polymer POEtOxMA revealed a strikingly similar response to the salts as linear PEtOx even though the cloud points of the polymers in water differ. This indicates that the architecture does not significantly influence the effect of the Hofmeister ions, even though there is a difference in the absolute cloud point.
New multifunctional copoly(2‐oxazoline) nanoparticles were prepared for cell studies. The polymer contains double‐bond side chains as potential reaction sites for “thio”‐click reactions as well as a fluorescein label covalently bound to the polymer backbone. Using the nanoprecipitation technique, spherical nanoparticles of 200–800 nm were obtained. Confocal laser scanning microscopy measurements revealed the cellular uptake of the nanoparticles.
This feature article provides, for the first time, an overview of the research that guided the way from fundamental studies of the thermo-responsive phase separation of aqueous polymer solutions to polymeric sensor systems. The incorporation of solvatochromic dyes into thermoresponsive polymers as well as the concepts of polymeric sensors are presented and discussed in detail. 相似文献
In this study liquid chromatography at critical conditions for poly(2-ethyl-2-oxazoline)s (PEtOx) has been performed for the first time in order to analyze functional PEtOx homopolymers and block copolymers. Besides the verification of the critical point of adsorption with two series of ester end group functionalized PEtOx homopolymers, to evaluate the effect of both the chain length dependence and the end group polarity, using a cyano column with a solvent combination of 2-propanol and water, also two-dimensional liquid chromatography (2D-LC) has been applied for a poly(2-oxazoline) block copolymer. The combined characterization techniques provided further information about the polymerization procedure with regard to the formation of side-products by separation of the block copolymer from the corresponding homopolymer impurities. In addition, hyphenation of LCCC with MALDI-TOF MS and ESI-Q-TOF tandem mass spectrometry verified the obtained results. 相似文献
A liquid chromatography–particle-beam mass spectrometer (LC–PB/MS) with interchangeable electron-impact (EI) and glow-discharge
(GD) ion sources was evaluated for future application in analysis of botanical extracts. In this work a green tea tincture
was characterized for a series of catechin components (catechin, epicatechin, epigallocatechin, and epigallocatechin gallate
(EGCG)) and caffeine. Special emphasis was given to EGCG and caffeine, because they are important in determining the possible
health effects of the green tea. The effects of instrument operating conditions were evaluated for the EI and GD ionization
sources to determine their effect on analyte intensities and fragmentation patterns. These studies furnished information about
the effects of these conditions in determining possible ionization pathways in the two ion sources. The mass spectra of these
compounds obtained with the GD ion source are EI-like in appearance, with clearly identified molecular ions and fragmentation
patterns that are easily rationalized. The absolute limits of detection for EGCG and caffeine were, respectively, 11 ng and
0.77 ng for the EI source and 3.2 ng and 0.61 ng for the GD source. The PB/EIMS and PB/GDMS combinations can be operated in
a flow-injection mode, wherein the analyte is injected directly into the mobile phase, or coupled to high-performance liquid
chromatography (HPLC), enabling LC–MS analysis of complex mixtures. A reversed-phase chromatographic separation of the green
tea tincture was performed on a commercial C18 column using a gradient of water (containing 0.1% TFA) and ACN. Quantification of EGCG and caffeine was performed by the
standard addition method. The amounts of EGCG and caffeine in the tested green tea tincture were each ∼14 mg mL−1. 相似文献