Facile, controlled, room-temperature RAFT polymerization of N-isopropylacrylamide.
ABSTRACT Poly(N-isopropyl acrylamide) is a thermoresponsive polymer that has been widely investigated for drug delivery. Herein, we report conditions facilitating the controlled, room-temperature RAFT polymerization of N-isopropylacrylamide (NIPAM). The key to success is the appropriate choice of both a suitable RAFT chain transfer agent (CTA) and initiating species. We show that the use of 2-dodecylsulfanylthiocarbonylsulfanyl-2-methyl propionic acid, a trithiocarbonate RAFT CTA, in conjunction with the room-temperature azo initiator 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), in DMF, at 25 degrees C, yields conditions leading to NIPAM homopolymerizations which bear all of the characteristics of a controlled/"living" polymerization. We also demonstrate facile size exclusion chromatographic analysis of PNIPAM samples in DMF at 60 degrees C, directly on aliquots withdrawn during the polymerizations, which avoids the problems previously reported in the literature.
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ABSTRACT: We have measured the pro-oxidant-antioxidant-balance (PAB) levels in patients with defined coronary artery disease (CAD) and compared them with concentrations in healthy subjects. Based on angiography results, 400 patients with stable CAD were divided into CAD- and CAD+, this being further subcategorized into groups with single-, double- and triple-vessel disease (VD). The mean PAB values in the healthy subjects, was significantly lower than for other groups (P<0.001). In CAD- patients, PAB levels were 123.2 ± 43.9, which was not statistically different compared to groups with SVD, 2VD and 3VD (P>0.05). In the CAD+ group, PAB values in 1VD, 2VD and 3VD were not significantly different among patients with SVD, 2VD and 3VD (P>0.05). In conclusion, we found higher levels of oxidative stress in CAD+ patients compared to healthy subjects. The oxidation level was not related to measures of the extent of CAD such as number of stenosed vessels.Clinical biochemistry 08/2011; 44(16):1304-8. · 2.02 Impact Factor
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ABSTRACT: An attractive concept for designing "smart materials" is the combination of supramolecular interactions with thermoresponsive polymers. Here, this concept is illustrated by preparing aqueous micelles from poly(N-isopropylacrylamide)-block-polystyrene copolymers functionalized at the extremity of their poly(N-isopropylacrylamide) coronal chains by terpyridine ligands. The effect of temperature and of the addition of Zn(II) ions on the self-assembling properties is then studied.Macromolecular Rapid Communications 12/2011; 33(6-7):534-9. · 4.93 Impact Factor
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ABSTRACT: We report on the synthesis and self-assembly behavior of a well-defined double hydrophilic brush-coil copolymer with poly(N-isopropylacrylamide)-b-poly(glycidly methacrylate) (PNIPAM-b-PGMA) as backbone and poly(l-glutamic acid) (PLGA) as brush. The PNIPAM-b-PGMA was firstly prepared by the sequential reversible addition-fragmentation chain transfer polymerization of N-isopropylacrylamide and glycidly methacrylate. The obtained diblock copolymer was reacted with ethylenediamine (EDA) yielding the aminated macroinitiator (PNIPAM-b-PGMA-EDA), which was then used to initiate ring-opening polymerization of γ-benzyl-l-glutamate-N-carboxyanhydride (BLG-NCA) to give PNIPAM-b-(PGMA-g-PBLG) copolymer. After the deprotection of benzyl groups on PBLG, double hydrophilic brush-coil copolymer, PNIPAM-b-(PGMA-g-PLGA), was obtained. The thermo- and pH-responsive micellization behaviors of PNIPAM-b-(PGMA-g-PLGA) in aqueous solution were investigated by fluorescence spectroscopy, 1H NMR, dynamic light scattering, scanning electron microscopy, and circular dichroism. It can self-assemble into PNIPAM-core micelles at pH 10 and elevated temperature and PLGA-core micelles at pH 4 and room temperature. Such brush-coil copolymers have the potential applications as biomedical and intelligent materials.Journal of Colloid and Interface Science 02/2013; · 3.17 Impact Factor