Search results for "copolymer"
showing 10 items of 1003 documents
Mixed aggregates based on tetronic-fluorinated surfactants for selective oils capture
2015
Abstract An aqueous star-like copolymer solution was titrated with perfluoro carboxylic acids at various compositions to prepare a polymeric surfactant composed of fluorinated nano-domains. The copolymer is X-shaped where each arm contains ethylene oxide and propylene oxide repetitive units linked to a central ethylenediamine group. The aggregation behavior of the hybrid macromolecule was studied from the physico-chemical point of view by changing parameters like temperature and composition. The solubilization of perfluorinated and hydrogenated alcohols in mixed self-assembled structure revealed that a selectivity toward the fluorinated moiety can be done. The self-assembled structures are …
New Self-Assembling Polyaspartamide-Based Brush Copolymers Obtained by Atom Transfer Radical Polymerization
2009
A simple and efficient method for the synthesis of polyaspartamide-based brush copolymers using Atom Transfer Radical Polymerization (ATRP) is here presented. The syntheses were performed by using two subsequent steps. In the first step the macroinitiator was obtained by the conjugation of a proper number of 2-bromoisobutyryl bromide (BIB) residues to the R, -poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA) side chains, obtaining the PHEA-BIB copolymer. PHEA-BIB copolymer was used as “multi-functional macroinitiator” for the polymerization via ATRP of hydrophilic methacrylic monomers, such as methacrylic acid (MA), obtaining PHEA-IB-poly(MA) copolymer, sodium methacrylate (MANa+), obtaining PH…
Multiarm star polyglycerol-block-poly(HEMA) as a versatile precursor for the preparation of micellar nanocapsules with different properties
2007
Well-defined multiarm star polymer with hyperbranched polyglycerol as core and poly(2-hydroxyethyl methacrylate) (PHEMA) as arms were used as precursor for the preparation of inverted and aqueous micellar nanocapsules. The partial modification of the hydroxyl groups of PHEMA arms with aliphatic chains led to the formation of inverted micellar nanocapsules. The hydrophilic dye encapsulation capacity of the inverted micelles can be enhanced significantly by transforming the inner hydroxyl groups of PHEMA arms into quaternized amine groups. The modification of the outer and inner hydroxyl groups of PHEMA arms with polyethylene glycol acid chloride and pivaloyl chloride, respectively, resulted …
A Nanoparticulate Drug-Delivery System for Rivastigmine: Physico-Chemical and in vitro Biological Characterization
2007
The preparation and characterization of surface-PEGylated polymeric nanoparticles are described. These systems were obtained by UV irradiation of PHM and PHM-PEG 2000 as an inverse microemulsion, using an aqueous solution of the PHM/PHM-PEG 2000 copolymer mixture as the internal phase and triacetin saturated with water as the external phase, and characterized by dimensional analysis, zeta-potential measurements and XPS. in vitro biological tests demonstrated their cell compatibility and their ability to escape from phagocytosis. Rivastigmine was encapsulated into the nanoparticle structure and drug-release profiles from loaded samples were investigated in PBS at pH = 7.4 and human plasma.
Novel water-swellable beads based on an acryloylated polyaspartamide
2001
Spherical polymeric microparticles have been prepared by a reverse-phase suspension polymerization technique. The starting polymer was α,β-poly (N-2-hydroxyethyl)-dl-aspartamide (PHEA) partially functionalised with glycidylmethacrylate (GMA) in order to introduce reactive vinyl groups in the side chain. The PHEA–GMA copolymer obtained (PHG) was cross-linked in a mixture of water/hexane–carbon tetrachloride in the presence of sorbitan trioleate (Span 85) as surfactant and ammonium persulfate/N,N,N′,N′-tetramethylethylenediamine as initiator system. The reaction was also carried out in the presence of N,N′-dimethylacrylamide as comonomer or N,N′-ethylenebisacrylamide as a cross-linking agent.…
Investigation of the Interpolymer Complex between Hydroxypropyl Cellulose and Maleic Acid-Styrene Copolymer, 1
2004
The hydrogen bonding-interpolymer association of hydroxypropyl cellulose (HPC) with maleic acid-styrene (MAc-S) copolymer has been investigated in dilute aqueous solution by viscometry, turbidimetry and potentiometry. At a mixing ration between MAc-S and HPC of 10:90, the solution exhibits a phase separation upon heating, while for other mixing ration no phase separation could be detected. The stability of the interpolymer complex (IPC) increases as the temperatures rises. The stoichiometry of the IPC, in mole units, was estimated as being MAc-S:HPC=5:2. The thermodynamic functions (enthalpy and entropy) of the complexation process have been determined.
NEW GRAFT COPOLYMERS OF HYALURONIC ACID AND POLYLACTIC ACID: SYNTHESIS AND CHARACTERIZATION
2006
Abstract New graft copolymers have been synthesized, using hyaluronic acid (HA) as a hydrophilic backbone and polylactic acid (PLA) as an aliphatic polyester in order to obtain new polymeric derivatives of HA able to hydrophobically associate in an aqueous medium. Hyaluronic acid with low molecular weight was made soluble in organic solvent by transformation to its tetrabutylammonium (TBA) salt. Using the HA–TBA derivative, the reaction was performed in dimethylsulfoxide adding as a reagent the N -hydroxysuccinimide derivative of PLA. Two HA–PLA graft copolymers have been synthesized and characterized by FT-IR, 1 H NMR spectroscopy and gel permeation chromatography. The interaction between …
New trials in the consolidation of waterlogged archaeological wood with different acetone-carried products
2011
Some acetone-carried consolidants for waterlogged archaeological wood were tested in order to evaluate treatments able to save time and energy. In details, colophony (rosin), two esterified colophonies (Rosin 100® and Rosin 459®), a mixture of colophony with PEG 3400 and a vinyl acetate - vinyl versate copolymer (Vinavil 8020S®) were tested. The treatments were carried out at temperatures of 20 and 35 °C on waterlogged maritime pine, elm, oak and beech. The materials came from the archaeological Site of the ancient ships of Pisa (Tuscany, Italy) and were dated back to VII cent. BC II cent. AD. To evaluate the processes, equilibrium moisture content and dimensional stability of treated woo…
Amphiphilic Polysaccharide Block Copolymers for pH-Responsive Micellar Nanoparticles
2017
A full polysaccharide amphiphilic block copolymer was prepared from end group-functionalized dextrans using copper-mediated azide-alkyne click chemistry. Sufficient modification of the reducing end in both blocks was achieved by microwave-enhanced reductive amination in a borate-buffer/methanol solvent system. The combination of a hydrophilic dextran block with a hydrophobic acetalated dextran block results in an amphiphilic structure that turns water-soluble upon acid treatment. The material has a low critical micelle concentration and self-assembles in water to spherical micellar nanoparticles. The formed nanoparticles have a narrow size distribution below 70 nm in diameter and disassembl…
Copolymerization of Polythiophene and Sulfur To Improve the Electrochemical Performance in Lithium–Sulfur Batteries
2015
We first report on the copolymerization of sulfur and allyl-terminated poly(3-hexylthiophene-2,5-diyl) (P3HT) derived by Grignard metathesis polymerization. This copolymerization is enabled by the conversion of sulfur radicals formed by thermolytic cleavage of S8 rings with allyl end-group. The formation of a C–S bond in the copolymer is characterized by a variety of methods, including NMR spectroscopy, size exclusion chromatography, and near-edge X-ray absorption fine spectroscopy. The S-P3HT copolymer is applied as an additive to sulfur as cathode material in lithium–sulfur batteries and compared to the use of a simple mixture of sulfur and P3HT, in which sulfur and P3HT were not covalent…