Search results for "modification"
showing 10 items of 853 documents
Some examples of the modification of polymers
1986
Reactions avec des groupes amide et amino dans la chaine principale, et avec un groupe terminal bromoacetyl. Polymerisation de la conidine en presence d'un polystyrene vivant
Synthesis and characterisation of novel chemical conjugates based on alpha, beta-polyaspartylhydrazide and beta-cyclodextrins
2006
A new family of supramolecular systems based on a synthetic polyaminoacid and cyclic oligosaccharides such as beta-cyclodextrins (beta-CDs) was synthesised. The pharmaceutical potential of these systems arises from the proper combination between the complexing properties of cyclodextrins and the particular pharmacokinetic profile that can be obtained by using macromolecular conjugates with a biocompatible backbone. Five supramolecular conjugates were synthesised by using alpha,beta-polyaspartylhydrazide (PAHy) as a polymeric component and various amounts of two P-CD derivatives. In particular, by reaction of PAHy with beta-CD monoaldehyde, samples named as A(1), A(2) and A(3), bearing, resp…
Synthesis, characterisation and properties of α,β-poly(N-2-hydroxyethyl)-dl-aspartamide-graft-maleic anhydride precursors and their stimuli-responsiv…
2009
Abstract A family of poly(amino acid)-maleic anhydride hydrogels were designed and synthesized. Water soluble polymeric precursors were prepared by partially substituting the hydroxyl groups of the α,β-poly( N -2-hydroxyethyl)- dl -aspartamide backbone with maleic anhydride, so as to provide double bonds for crosslinking and carboxylic acid groups for pH and electric field responsiveness. Reaction conditions (reactive mixture composition and catalysis) were systematically varied in order to obtain PHEA–MA precursors with different and reliable graft-maleic anhydride levels. PHEA–MA precursors were characterised by titration, Nuclear Magnetic Resonance ( 1 H NMR), Fourier-Transformed Infrare…
Synthesis of aldonamide siloxanes by hydrosilylation
1998
Abstract The synthesis of hydrophobic/hydrophilic hybrid polymers based on polydimethylsiloxanes (PDMS) and carbohydrate derivatives involving a hydrosilylation step is reported. Starting with poly(dimethyl- co -hydromethyl)siloxanes (PDMS- co -HMS), O -acetylated N -allylaldonamides of various sugars can be attached to the siloxane backbone using platinum catalysts. The characteristics of different transition metal complexes in the polymer-analogous formation of SiC bonds are investigated. A generalized reaction pathway applicable to several reducing carbohydrates is established to synthesize aldonamide siloxanes in a broad variety of molecular weight and composition. The products obtaine…
Cationic copolymers of ?,?-poly-(N-2-hydroxyethyl)-DL-aspartamide (PHEA) and ?,?-polyasparthylhydrazide (PAHy): synthesis and characterization
2000
In the present study the derivatization of two water-soluble synthetic polymers, α,β-poly(N-2-hydroxyethyl)-DL-aspartamide (PHEA) and α,β-polyasparthylhydrazide (PAHy), with glycidyltrimethylammonium chloride (GTA) is described. This reaction permits the introduction of positive charges in the macromolecular chains of PHEA and PAHy in order to make easier the electrostatic interaction with DNA. Different parameters affect the reaction of derivatization, such as GTA concentration and reaction time. PHEA reacts partially and slowly with GTA; on the contrary the reaction of PAHy with GTA is more rapid and extensive. The derivatization of PHEA and PAHy with GTA is a convenient method to introdu…
Multilayer build-up of a reactive polymer with α,ω-functionalized chromophores
1997
Alternating multilayers with up to ten layers have been prepared by sequential reaction of a reactive polymer (poly[(1-methylvinyl isocyanate)-alt-(maleic anhydride)]) with α,ω-functionalized chromophores. For this purpose new chromophores were synthesized varying the length of the hydrophobic spacer. The analysis of the multilayer build-up shows that physisorption is more important than chemisorption for fixation of new polymer layers. Thus, a multilayer build-up is only possible with the shorter, more hydrophilic chromophore and not with the long hydrophobic spacer.
Synthesis and polymerization of active ester monomers based on 4-vinylbenzoic acid
2007
Abstract Nine active ester monomers based on 4-vinylbenzoic acid have been synthesized. Under free radical polymerization conditions these monomers could successfully be polymerized yielding reactive polymers with molecular weights of around M n = 20.000–50.000 g/mol and molecular weight distributions M w / M n of around or below 2 in good yields. Polymer analogous reactions with amines have been investigated by time-resolved FT-IR spectroscopy and it was found that especially poly(pentafluorophenyl 4-vinylbenzoate) featured a significant reactivity, such that polymer analogous reactions proceeded quantitatively with amines within less than 5 min at 0 °C.
Versatile ω-end group functionalization of RAFT polymers using functional methane thiosulfonates
2009
Five different polymers, poly[methyl methacrylate] (PMMA), poly[lauryl methacrylate] (PLMA), poly[diethylene glycol methacrylate] (PDEGMA), poly[N-iso-propylacrylamide] (PNIPA), and poly[styrene] (PS) prepared by the RAFT process and thus terminated with dithioesters were aminolyzed in the presence of S-3-butynyl methane thiosulfonate (MTS), which was synthesized in two steps. Analysis of the polymers by 2D NMR, UV–vis absorbance, and gel permeation chromatogra-phy revealed them to quantitatively carry acetylene end groups connected with disul-fide bridges, indicating that functional MTS reagents can be employed for end group functionalization of RAFT polymers. This versatile method is of ad…
pH-sensitive hydrogel based on a novel photocross-linkable copolymer.
2004
A pH sensitive hydrogel has been prepared by a UV irradiation technique. Starting polymer was the PHM (poly hydroxyethylaspartamide methacrylated) obtained from polyaspartamide (PHEA) partially derivatized with methacrylic anhydride (MA). This new copolymer has been further derivatized with succinic anhydride (SA) to obtain PHM-SA that has been cross-linked by UV irradiation to form a pH sensitive hydrogel. The network, recovered after washing as a powder, has been been characterized by FT-IR spectrophotometry and particle size distribution analysis. Moreover, to have information about water affinity of the prepared sample, swelling measurements have been carried out in aqueous media mimick…
Gamma radiation induced maleation of polypropylene using supercritical CO 2 : preliminary results
2000
Abstract The charging of maleic anhydride (MA) and dicumyl peroxide (DCP) into polypropylene matrices has been carried out by CO2 in supercritical conditions. The grafting of MA into polymer chains was done through gamma irradiation in CO2 atmosphere (0.1 MPa, 25°C). The grafting was successful and the amount of grafted anhydride was dependent on the amount of MA and DCP charged into the polypropylene matrix. The presence of grafted succinic anhydride was shown by FT-IR spectroscopy and its amount was determined through a calibration curve derived from standard samples. The effect of swelling due to supercritical CO2, maleic anhydride grafting and gamma irradiation on the molecular structur…