Search results for "cationic polymerization"
showing 10 items of 441 documents
Micelles of polyisobutylene-block-poly(methacrylic acid) diblock copolymers and their water-soluble interpolyelectrolyte complexes formed with quater…
2004
The micellization of ionic amphiphilic diblock copolymers, polyisobutylene-block-poly(methacrylic acid) (PIB-b-PMAA), with a constant degree of polymerization of the non-ionic block ðDPn ¼ 20Þ and various degrees of polymerization of the polyelectrolyte block ðDPn ¼ 100 – 425Þ was examined in aqueous media by means of fluorescence spectroscopy using pyrene as a polarity probe. The molar values of the critical micellization concentration (cmc) were found to be around 2 £ 10 26 mol/l, being nearly independent of the length of the polyelectrolyte block as well as pH (in the range 6 – 9) and ionic strength (# 0.5 M NaCl) while the specific cmc values varied from 20 to 100 mg/l. Small-angle neut…
1990
It is shown that the block-like structure of the polyampholyte poly(methacrylic acid)-block-poly(1-methyl-4-vinylpyridinium chloride) considerably influences its conformational behaviour. This specific behaviour is explained by the formation of intra-macromolecular polyelectrolyte complexes stabilized by cooperative ionic contacts between acidic and basic units near the isoelectric point (i. e. p.). The structure of the block-polyampholyte at the i. e. p. is suggested to be close to the structure of non-stoichiometric polyelectrolyte complexes. The complex formation ability of the block-polyampholyte with respect to anionic, cationic, and nonionic polymers is also studied. By means of poten…
Gold nanostars coated with neutral and charged polyethylene glycols: A comparative study of in-vitro biocompatibility and of their interaction with S…
2015
Gold nanostars (GNS) have been coated with four different polyethylene glycols (PEGs) equipped with a -SH function for grafting on the gold surface. These PEGs have different chain lengths with average MW = 2000, 3000, 5000 and average number of -O-CH2-CH2 - units 44, 66, and 111, respectively. Two are neutral and two are terminated with -COOH and -NH2 functions, thus bearing negative and positive charges at physiological pH, thanks to the formation of carboxylate and ammonium groups. The negative charge of the GNS coated with PEG carboxylate has also been exploited to further coat the GNS with the PAH (polyallylamine hydrochloride) cationic polymer. Vitality tests have been carried out on …
Hyperbranched polyethylenimines as versatile precursors for the preparation of different type of unimolecular micelles
2007
Abstract Hyperbranched polyethylenimine (HPEI) was successfully employed as precursor for the preparation of unimolecular inverted and aqueous micelles. The unimolecular inverted micelles (UIMs) obtained by the amidation of HPEI with 1,1′-carbonyldiimidazole (CDI) activated palmitic acid exhibited high encapsulation efficiency for hydrophilic anionic dyes and the efficiency could be enhanced significantly by decreasing the degree of amidation or quaternizing the residual amines. The weight ratio of loaded guests to the amidated HPEIs was not dependent on the molecular weight of HPEI core when the degree of amidation was kept constant. Decreasing the length of the aliphatic chain from 16 to …
Polymerisation und Kettenverknüpfung von Alkenyl-1,2,3-thiadiazolen
1986
4- und 5-Vinyl-1,2,3-thiadiazole 1, 2 lassen sich in radikalischen oder kationischen Kettenreaktionen polymerisieren. Die dabei vollstandig intakt bleibenden Thiadiazolringe konnen photochemisch abgebaut werden, wobei es zur Kettenvernetzung uber substanzeigene S-Brucken kommt. Das 5-Vinylsystem 2 kann mit 4,4′-(1,6-Hexandiyl)bis(4H-1,2,4-triazol-3,5-dion) unter Denitrogenierung copolymerisiert werden. Polymerization and Cross-Linking of Alkenyl-1,2,3-thiadiazoles 4- and 5-Vinyl-1,2,3-thiadiazoles 1, 2 can be polymerized in radical or cationic chain processes. The completely intact remaining thiadiazole ring systems can be photochemically cleaved yielding a cross-linking of the polymer chai…
The apparently anomalous effects of surfactants on interfacial tension in the IBA/water system near its upper critical solution temperature
2016
We studied the effect of anionic, cationic, and nonionic surfactants on the interfacial tension between the two phases of the isobutyric acid/water system using spinning drop tensiometry. It has been found that interfacial tension decreases with increasing concentration of the surfactant in the case of sodium dodecyl sulfate (SDS) and of dodecyltrimethylammonium chloride (DTAC). However, in the case of Triton X-100 an increase of surfactant concentration leads to an increase of the interfacial tension. Such results are consistent with the upper critical solution temperature (UCST) in the presence of these surfactants: the UCST decreases with increasing SDS and DTAC concentrations while it i…
New copolymers graft of α,β-poly(N-2-hydroxyethyl)-d,l-aspartamide obtained from atom transfer radical polymerization as vector for gene delivery
2012
Abstract New cationic α,β-poly(N-2-hydroxyethyl)- d , l -aspartamide (PHEA) graft copolymers were synthesized by ATRP, using diethylamino ethyl methacrylate (DEAEMA) as monomer for polymerization, yielding polycations (PHEA-pDEAEMA) able to condense DNA. Then, consecutive ATRP conditions were set up on PHEA-pDEAEMA to obtain copolymers containing also hydrophilic chains (PHEA-IB-pDMAEMA-pPEGMA) able to improve biocompatibility of polyplexes and to provide them stealth properties. Agarose gel studies showed that the copolymers effectively condensed plasmid DNA to form polyplexes. Light scattering studies were used to analyze the size and the ζ -potential of these polyplexes, showing that cop…
Kinetic Analysis of “Living” Polymerization Systems Exhibiting Slow Equilibria. 3. “Associative” Mechanism of Group Transfer Polymerization and Ion P…
1996
The averages of the molecular weight distribution are derived for a “living” polymerization process which proceeds via active and “dormant” species and where the active species are formed by addition of a catalyst to a “dormant” species. Such a mechanism is applicable to group transfer and “living” cationic polymerizations (assuming that ion pairs are formed exclusively in the latter case). Both equilibrium and nonequilibrium initial conditions are used for the calculation. The results are very similar to those obtained for degenerative transfer (i.e., direct exchange of activity between active and “dormant” species). The dominating parameter is β = k2/(kpI0), where k2 and kp are the rate c…
Bioreducible Poly-l-Lysine-Poly[HPMA] Block Copolymers Obtained by RAFT-Polymerization as Efficient Polyplex-Transfection Reagents
2015
Polylysine-b-p[HPMA] block copolymers containing a redox-responsive disulfide bond between both blocks are synthesized by RAFT polymerization of pentafluorphenyl-methacrylate with a macro-CTA from Nϵ-benzyloxycarbonyl (Cbz) protected polylysine (synthesized by NCA polymerization). This polylysine-b-p[PFMA] precursor block copolymer is converted to polylysine(Cbz)-b-p[HPMA] by postpolymerization modification with 2-hydroxypropylamine. After removal of the Cbz protecting group, cationic polylysine-b-p[HPMA] copolymers with a biosplittable disulfide moiety became available, which can be used as polymeric transfection vectors. These disulfide linked polylysine-S-S-b-p[HPMA] block copolymers sho…