Application possibilities of preparative size exclusion chromatography to analytical problems in polymer science

The application possibilities of preparative size exclusion chromatography for the detailed analysis of polymer analytes is discussed. Using the example of a star-shaped polymer architecture, the possibilities of utilizing fractions obtained from preparative size exclusion chromatography and their subsequent off-line characterization with a variety of hyphenated analytic techniques are discussed and compared to one another. It was, for instance, possible to obtain an absolute SEC calibration for the investigated star-shaped polymers that showed very good agreement with theoretical expected values and values obtained by absolute molecular weight determination techniques by analyzing fractions of different molecular weights of this polymer architecture by MALDI-TOFMS in order obtain the Mp values required for SEC calibrations. Moreover, the star-shaped polymers were investigated by SEC-viscometry in order to obtain their absolute molecular weight. All analytical results are compared to each other and possibilities as well as limitations are discussed

Microwave-assisted synthesis and properties of novel poly(2-oxazoline)s

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Synthesis, characterization and cross-linking of a library of statistical copolymers based on 2-"soy alkyl"-2-oxazoline and 2-ethyl-2-oxazoline

The synthesis of statistical copolymers consisting of 2-ethyl-2-oxazoline (EtOx) and 2-‘‘soy alkyl’’-2-oxazoline (SoyOx) via a microwave-assisted cationic ringopening polymerization procedure is described. The majority of the resulting copolymers revealed polydispersity indices below 1.30. The reactivity ratios (rEtOx 1.4 6 0.3; rSoyOx ¼ 1.7 6 0.3) revealed a clustered monomer distribution throughout the polymer chains. The thermal and surface properties of the pEtOx-stat-SoyOx copolymers were analyzed before and after UV-curing demonstrating the decreased chain mobility after cross-linking. In addition, the cross-linked materials showed shape-persistent swelling upon absorption of water from the air, whereby as little as 5 mol % SoyOx was found to provide efficient cross-linking

New preparation and purification methods for metallo-supramolecular block copolymers

The bis-complex formation of two terpyridine-modified polymers using microwave assisted reaction conditions was investigated in detail. In order to construct a heteroleptic block copolymer polystyrene, which was prepd. by nitroxide-mediated radical polymn. (NMRP), and a com. available poly(ethylene oxide) were used. These studies include the influence of temp., reaction time, concn. and the use of different solvent mixts. on complexation. The conversion was detd. by GPC measurements. The amphiphilic metallo-supramol. block copolymers were investigated towards their formation of micellar aggregates in water. Other characterization techniques include 1H-NMR, UV/vis spectroscopy, dynamic light scattering (DLS), at. force spectroscopy (AFM) and transmission electron microscopy (TEM) techniques

Application possibilities of preparative size exclusion chromatography in a HTE workflow

Abstract onl

Morphologies of spin-coated films of a library of diblock copoly(2-oxazoline)s and their correlation to the corresponding surface energies

The influence of surface morphologies on the properties of materials is of essential importance and is therefore a widely discussed topic. In the present contribution, the properties of a set of diblock copoly(2-oxazoline)s are analyzed in terms of their individual morphologies, which have been investigated with tapping-mode SFM. This collection of diblock copolymers consists of 12 diblock copolymers and four corresponding homopolymers, representing a complete 16-membered library of (co-) poly(2-oxazoline)s, composed of four differently substituted 2-oxazoline monomers. For the investigated set of compounds, a correlation between the morphologies of the spin-coated films and their surface energies could be determined

Tunable pH- and temperature-sensitive copolymer libraries by reversible addition-fragmentation chain transfer copolymerizations of methacrylates

Reversible addn.-fragmentation chain transfer (RAFT) polymns. were performed on a Chemspeed Accelerator SLT100 automated synthesizer to polymerize N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and poly(ethylene glycol) Me ether methacrylate (PEGMA) at 70 DegC. Azobis(isobutyronitrile) (AIBN) was used as source of radicals and 2-cyano-2-Bu dithiobenzoate (CBDB) as RAFT agent. A complete screening in compn. of P(DMAEMA-stat-PEGMA) copolymers was elaborated from 0% of PEGMA to 100% of PEGMA. All polydispersity indexes of the obtained copolymers are comprised between 1.11 and 1.30. The reactivity ratios were detd. by the extended Kelen-Tuedoes method (rDMAEMA = 0.93 and rPEGMA = 0.66). The behavior of the pH- and temp.-sensitive copolymers was studied in aq. soln. by measuring the lower crit. soln. temp. (LCST) by UV/vis spectroscopy. The measurements were performed at three different pH values (4, 7, and 10). At pH 7 and pH 10 the LCST is increasing linearly with the wt. % PEGMA in the copolymer feed. On the contrary, at pH 4, the hydrophilicity of the P(DMAEMA-stat-PEGMA) copolymers is too high due to the protonation of the DMAEMA units. Thus, no LCST was detected for most of them. By varying the pH and the compn. of the P(DMAEMA-stat-PEGMA) copolymers, the LCST can be easily tuned between 34.7 and 82.0 DegC

Tuning solution polymer properties by binary water–ethanol solvent mixtures

The solubility of polymers can be significantly altered by the use of solvent mixtures. The solvent composition also effects the self-assembly properties of amphiphilic copolymers. In addition, water–ethanol mixtures are known to exhibit abnormal physicochemical properties due to the presence of hydration shells around the ethanol molecules, while at the same time both solvents have very low toxicity. However, the solution properties of amphiphilic copolymers in water– ethanol mixtures have been scarcely studied. Here we show that the solution polymer properties of amphiphilic copoly(2-oxazoline)s can be significantly altered in binary water–ethanol mixtures resulting in increased solubility, tuneable lower critical solution temperatures as well as polymer– solvent combinations with both a LCST followed by an UCST and improved dispersion stability. Surprisingly, it was found that polymers insoluble in both ethanol and water could be dissolved in water–ethanol mixtures, opening the way to novel formulations for drug delivery or personal care applications. Our results represent a straightforward method for tuning solution polymer properties without the synthetic efforts that are generally required to change the copolymer composition and propertie

Selective partial hydrolysis of amphiphilic copoly(2-oxazoline)s as basis for temperature and ph responsive micelles

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