[Show abstract][Hide abstract] ABSTRACT: There is an increasing need for smart materials capable of removing multivalent ions from aqueous streams without the inconvenience of brine regeneration as in ion-exchange processes. Herein, we present a thermoresponsive micellar system consisting of polystyrene-poly(methoxy diethyleneglycol acrylate) block copolymer surfactants modified with carboxylic acid end groups (PS-PMDEGA-COOH) that can be used to switch between the adsorption and desorption of divalent calcium(II) cations by a mild temperature trigger, thus providing a new type of thermoregenerable ion-adsorbing materials. The switch of calcium(II)-binding capacity is demonstrated to result from a shift in the pKa value of the carboxylic acid groups by the collapse and redissolution of the PMDEGA block and the associated change in local polarity.
[Show abstract][Hide abstract] ABSTRACT: The development of responsive and multiresponsive polymers is gaining interest as they enable the development of more and more complex responsive materials. In this contribution, the synthesis and solubility behavior of well-defined poly(methyl acrylate) (PMA) and poly(diethylene glycol ethyl ether acrylate) (PDEGEA) homopolymers as well as PMA-block-PDEGEA block copolymers is reported. At first, a solubility screening of the homopolymers in ethanol-water solvent mixtures was performed in a high-throughput experimentation (HTE) manner using parallel turbidimetry, which revealed that in 35 wt% ethanol PMA undergoes an upper critical solution temperature (UCST) phase transition while PDEGEA undergoes a lower critical solution temperature phase transition in this solvent mixture. Moreover, the thermoresponsive self-assembly of PMA-b-PDEGEA block copolymers in water and ethanol were investigated by turbidimetry and DLS revealing UCST-induced disassembly of the micelles in ethanol and LCST-induced clustering of the micelles in water. Finally schizophrenic behavior of the PMA-b-PDEGEA block copolymers in 35 wt% ethanol is demonstrated.
Full-text · Article · Apr 2015 · European Polymer Journal
[Show abstract][Hide abstract] ABSTRACT: The solubility behavior of well-defined poly(methyl acrylate) homopolymers as well as polystyrene-block-poly (methylacrylate) block copolymers is discussed in this contribution. A solubility screening in ethanol-water solvent mixtures was performed in a high-throughput manner using parallel turbidimetry revealing upper critical solution temperature behavior for poly(methyl acrylate). Moreover, the self-assembly behavior of the block copolymers into micellar structures was investigated by dynamic light scattering (DLS), transmission electron microscopy (TEM), and cryo-TEM revealing upper critical solution temperature switchability of the micelles, which was evaluated by DLS at different temperatures. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 3681-3687, 2011
No preview · Article · Sep 2011 · Journal of Polymer Science Part A Polymer Chemistry
[Show abstract][Hide abstract] ABSTRACT: a b s t r a c t The synthesis of well-defined block copolymers from styrene and methyl acrylate via ATRP is discussed in this contribution. Kinetic studies on these block copolymerizations as well as characterization studies were performed to investigate the monomer composition in the respective PS and PMA blocks. MALDI-TOF-MS was performed to clarify the exact number of repeating units of each block and the total number of units in the block copolymer. Block copolymers up to 22 kDa could be analyzed by MALDI-TOF-MS, whereby polymers with PMA as first block showed a large second distribution corresponding to PMA homopoly-mers. However, SEC demonstrated that only a small amount of homopolymer was present indicating that care needs to be taken with interpreting MALDI-TOF-MS data, which is a qualitative rather than a quantitative technique.
Full-text · Article · Aug 2010 · European Polymer Journal
[Show abstract][Hide abstract] ABSTRACT: Nitroxide-mediated radical polymerization has been used for the preparation of pentafluorostyrene (PFS) homopolymers and random copolymers of PFS and oligo(ethyleneglycol) methacrylate (OEGMA(8.5)). The poly(pentafluorostyrene) homopolymers were reacted with thiophenol at different ratios at room temperature in the presence of triethylamine. The "clicked" polymers were characterized by H-1 and F-19 NMR spectroscopy and size exclusion chromatography. Moreover, the copolymerization kinetics of the PFS and OEGMA(8.5) copolymers was followed, and the phase transition behavior of random copolymers with different compositions was discussed. Furthermore, copolymers of PFS and 2-(dimethylamino) ethyl methacrylate (DMAEMA) were prepared at various mole ratios, and the copolymer with a 10:90 ratio, respectively, was soluble in water at room temperature. Turbidimetry measurements were performed for PFS and OEGMA(8.5) or DMAEMA copolymers to determine their cloud points. Finally, the PFS and OEGMA(8.5) copolymer with a mole ratio of 60:40 was reacted further with thiophenol to increase the hydrophobic part in the copolymer. The cloud points of the obtained copolymers could be tuned from 87 to 33 degrees C by using not only the controlled radical polymerization but also the "click" reaction in a controlled fashion. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1278-1286, 2010
No preview · Article · Mar 2010 · Journal of Polymer Science Part A Polymer Chemistry
[Show abstract][Hide abstract] ABSTRACT: Micellization and micellar gel formation of poly(styrene)-block-poly(methyl methacrylate) [PS-b-PMMA] are demonstrated in a water-ethanol solvent mixture; full hydration of the PMMA causes a large radius of gyration resulting in micellar gel formation at only 1 wt% polymer concentration.
Full-text · Article · Oct 2009 · Chemical Communications