Search results for "PLASTICS"
showing 10 items of 2724 documents
Cyclodextrins in polymer synthesis: Free radical polymerization of cyclodextrin complexes withN-methacryloyl-11-aminoundecanoic acid orN-methacryloyl…
1998
The hydrophobic monomers N-methacryloyl-11 -aminoundecanoic acid (1) or N-methacryloyl-1-aminononane (2) were incorporated as guests into the cavity of heptakis(2,6-di-O-methyl)-β-cyclodextrin (Me 2 -β-CD) as a host, yielding the water compatible monomers N-methacryloyl-l 11-aminoundecanoic acid/ Me 2 -β-CD-complex (1a) and N-methacryloyl-1 -aminononane/Me 2 -β-Cl complex (2a). These complexes were polymerized radically in aqueous medium. The resulting polymers 1b and 2b which were obtained from the complexes 1a and 2a, are insoluble in water because of the unthreading of the cyclodextrin during the polymerization. The polymerization rate of 1a and 2a is high in comparison to the rate of th…
Cyclodextrins in polymer synthesis: free radical polymerisation of cyclodextrin complexes of cyclohexyl and phenyl methacrylate in aqueous medium
1998
The polymerisation mechanism of 2,6-dimethyl-β-cyclodextrin (Me2-β-CD) complexes of phenyl methacrylate (1) and cyclohexyl methacrylate (2) is described. The polymerisation of the complexes 1 a and 2a was carried out in water with potassium peroxodisulfate/potassium hydrogensulfite as initiator. The unthreading of the Me2-β-CD during the polymerisation led to water-insoluble poly(phenyl methacrylate) (1b) and poly(cyclohexyl methacrylate) (2b). By comparison, analogously prepared polymers from uncomplexed monomers 1 and 2 in homogeneous organic solvent (THF) with AIBN as radical initiator showed significantly lower viscosities and were obtained in lower yields in both cases.
Cyclodextrins in polymer synthesis: Free radical polymerization of methylated β-cyclodextrin complexes of methyl methacrylate and styrene, controlled…
2000
Methylated β-cyclodextrin (me-β-CD) was used to complex the hydrophobic monomers methyl methacrylate (1) or styrene (2) yielding the water-soluble 1 : 1-host/guest complexes methyl methacrylate/me-β-CD (1 a) and styrene/me-β-CD (2 a), respectively. In addition, the hydrophobic chain-transfer agent dodecanethiol (3) was complexed by two equivalents of me-β-CD yielding the water-soluble dodecanethiol/me-β-CD (3 a). The included monomers were polymerized in water by a free-radical mechanism in the presence of 3 a as the chain-transfer agent. The chain-transfer constants were determined. In order to evaluate these results, the chain-transfer constants of 3 were also determined in the case of th…
Cyclodextrins in Polymer Synthesis: Synthesis and Influence of Methylatedβ-Cyclodextrin on the Radical Polymerization Behavior of 1,1-Disubstituted 2…
2001
The chemical and enzymatic hydrolyses of 1,1-diethoxycarbonyl-2-vinylcyclopropane (1) were investigated. The product of the pig liver esterase (PLE)-catalyzed hydrolysis of 1 is a chiral trans monoester of 2-vinylcyclopropane dicarboxylic acid. New 1,1-disubstituted 2-vinylcyclopropane monomers (2a, b) were synthesized by the esterification of this ester. Methylated β-cyclodextrin was used to complex monomers 2a, b, yielding water-soluble 1 : 1 host/guest complexes. These complexes were polymerized in aqueous media by a free-radical ring-opening mechanism.
Supramolecular Nanocycles Comprisingβ-Cyclodextrin-click-Ferrocene Units: Rings of Rings of Rings
2010
We applied 1,3-dipolar cycloaddition to bind ethynylferrocene onto 6I-azido-6I-deoxycyclomaltoheptaose under microwave assisted conditions. The process was investigated by (1) H NMR, FT-IR spectroscopy, and MALDI-TOF mass spectrometry. The ability of the synthesized compound to self-organize to cyclic supramolecular structures was investigated by dynamic light scattering measurements and cryo-transmission electron microscopy.
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…
Branched Versus Linear Polyisoprene: Flory-Huggins Interaction Parameters for their Solutions in Cyclohexane
2009
Flory-Huggins interaction parameters were determined as a function of composition for solutions of linear and of branched polyisoprene in cyclohexane (CH) at 25, 45, and 65 °C by means of vapor pressure measurements (moderate to concentrated solutions) and by vapor pressure osmometry (dilute solutions). The results demonstrate that CH is a considerably worse solvent for branched polyisoprene than for the linear analog at all temperatures and at all compositions. This observation corroborates the expectation based on a recent phenomenological approach, which accounts explicitly for the incapability of the segments of an individual polymer molecule to spread out over the entire volume of the …
Microstructure and lateral diffusion in monolayers of polymerizable amphiphiles
1989
Lipid analogue amphiphilic molecules containing polymerizable units were investigated in monolayers at the air/water interface by using film balance measurements, fluorescence microscopy, and photobleaching techniques. The polymerizable groups (diene-, diyne-, and methacrylate units) were introduced into the hydrophobic alkyl chains or into the polar head of the amphiphilic molecules. In the case of the diene- and diyne-containing compounds the polymerizable units are incorporated into the hydrophobic alkyl chains, enabling them to form a two-dimensional network. Due to the free chain flexibility of the monomers the lateral mobility was comparable to that of saturated lipid analogues and de…
Polymer and Dye Probe Diffusion in Poly(methyl methacrylate) below the Glass Transition Studied by Forced Rayleigh Scattering
1999
By dissolving tracer quantities of 9,10-phenanthrenequinone (PQ) in poly(methyl methacrylate) (PMMA) it was possible to study by forced Rayleigh scattering (FRS) the tracer diffusion of the unbleached PQ as well as the photoproduct which is covalently bound to the PMMA molecules. The PMMA samples with molecular weights, Mw, of 103−105 were intermittently annealed at 80 °C for diffusion times of up to one year. From the results we conclude that polymer chain diffusion may be possible at temperatures more than 20 K below the glass transition temperature Tg, but further experiments are necessary, in particular, since we cannot exclude that our results are due to yet unexplained long time aging…
New Perspectives of HPMA-based Copolymers Derived by Post-Polymerization Modification
2014
Poly[N-(2-hydroxypropyl) methacrylamide] (HPMA) was one of the first polymers applied as polymer drug conjugate in the clinics. Since then many attempts have been made to expand the functionality of HPMA-based copolymers from advanced synthetic pathways to multiple biomedical applications. This Feature Article highlights multifunctional HPMA based copolymers prepared by controlled radical polymerization and subsequent post-polymerization modification of activated ester precursor polymers via aminolysis. This approach combines precise control of the polymer's microstructure (molecular weight, dispersity, block copolymer formation, end group functionalization) with an easy introduction of var…