Search results for " plastics"

Durability of Biodegradable Polymer Nanocomposites

2021

Biodegradable polymers (BP) are often regarded as the materials of the future, which address the rising environmental concerns. The advancement of biorefineries and sustainable technologies has yielded various BP with excellent properties comparable to commodity plastics. Water resistance, high dimensional stability, processability and excellent physicochemical properties limit the reviewed materials to biodegradable polyesters and modified compositions of starch and cellulose, both known for their abundance and relatively low price. The addition of different nanofillers and preparation of polymer nanocomposites can effectively improve BP with controlled functional properties and change the…

Double Thermoresponsive Block Copolymers Featuring a Biotin End Group

2010

A poly(oligo(ethylene glycol) monomethyl ether methacrylate)-block-poly(N-isopropyl methacrylamide) (POEGMA-b-PNIPMAM) block copolymer with a biotin end group on the PNIPMAM block as a biotarget was synthesized as a model system for temperature-controlled polymer immobilization. The synthesis was based on RAFT polymerization followed by postpolymerization modification of an activated ester precursor block and an exchange of the dithioester end group within one step. NMR, differential scanning calorimetry (DSC), dynamic light scattering (DLS), and turbidimetry measurements were performed to investigate the stimulus-responsive properties. The double thermoresponsive POEGMA-b-PNIPMAM with biot…

Anionic Polymerization of (Meth)acrylates in the Presence of Cesium Halide−Trialkylaluminum Complexes in Toluene

2001

The polymerization of methyl methacrylate and various acrylates initiated by ester enolates in the presence of cesium halide-trialkylaluminum complexes, Cs[Al n R 2n X] (n = 1, 2; R = Et, Bu'), in toluene has living and controlled character at -20 °C for methacrylates (X = Cl) and at -65 °C for n-butyl acrylate (X = F). Quantitative monomer conversions are usually reached, leading to polymers with narrow molecular weight distributions (M w /M n < 1.1). Kinetic investigations indicate a rather complex polymerization mechanism, and we assume an equilibrium between at least two active species. With this new initiating system, beside acrylate homopolymers, random and graft copolymers can be syn…

Cast multibilayer films from polymerizable lipids

1987

Characterization of sulfobetaine monomers by nuclear magnetic resonance spectroscopy: a note

1995

A set of zwitterionic monomers bearing the 3-ammoniopropanesulfonate moiety is analysed in CDCl3, CD3OD and D2O by one- and two-dimensional H-1 n.m.r. and C-13 n.m.r. spectroscopy. Absolute and relative positions of the n.m.r, signals are determined depending on the solvent used; the refined assignments of the signals in the vicinity of the ammonium group deviate from previously proposed assignments based on standard n.m.r, shift tables. Still, there is no convincing evidence for a special ring current effect due to a six-membered ring conformation of the betaine moiety.

Synthesis and characterization of bi-functional photorefractive polymers

2001

Abstract A novel bi-functional photorefractive acrylate polymer with pendant carbazolyl groups and azo derivatives as side chains was synthesized, in which azo derivatives as electro-optic chromophores and carbazolyl as photoconductive moiety were covalently linked on the acrylate backbone. Photorefractive experiments showed that a high two-beam coupling gain coefficient of 93 cm −1 , diffraction efficiency of 12% and electro-optic coefficient of 26 pm/V were obtained. With increasing writing beam's intensity, the two-beam coupling enhanced gradually, and then reached saturation. Using the method of four-wave mixing, the photoisomerization grating was observed.

Polymerizable and polymeric zwitterionic surfactants: 2. Surface activity and aggregation behaviour in aqueous systems

1991

Abstract The surfactant properties of a series of permanently zwitterionic monomers and polymers were studied with respect to structural variations. A strong influence of the molecular geometry on solubility and aggregation behaviour was observed, in particular for the polymers. Whereas all monomers were water-soluble and true surfactants, the water solubility of the polymers was restricted to selected geometries. Water-soluble polymers showed the properties of classical polysoaps, i.e. low surface activity and solubilization power for hydrophobic solutes. In contrast, water-insoluble polymers formed stable monolayers at the air-water interface and could be deposited onto solid substrates b…

Amphotropic Ionomers by Attachment of Secondary Amines to a Reactive Ester Polymer

2004

We report on the synthesis of polyacrylamides that were prepared by the reaction of a reactive ester polymer with a mesogen-containing secondary amine and N-methyl-piperazine. As the polymers do not form hydrogen bonds near the amide groups, their mobility is significantly higher than that of poly(N-monoalkylacrylamides). The initially nonionic polymer shows no liquid-crystalline behavior in bulk and in mixture with ethylene glycol. This is due to the low polarity difference between the different side chains. The polarity difference can be increased by protonation or quarter-nization of the tertiary amino groups, and liquid-crystalline behavior is observed. The self-assembly multilayer buil…

Controlled synthesis of poly(acetone oxime acrylate) as a new reactive polymer: Stimuli-responsive reactive copolymers

2007

Abstract Acetone oxime acrylate has been synthesized as a new active ester monomer. Free radical polymerization yielded a reactive polymer soluble in various organic solvents, such as chloroform, dioxane, DMSO, acetone, methanol, dichloromethane, DMF, and ethanol. Controlled radical polymerization of acetone oxime acrylate was successfully conducted using the RAFT, NMP and Iniferter method. Partly polymer analogous reaction with N-isopropylamine resulted in the reactive copolymer poly(N-isopropylacrylamide-co-acetone oxime acrylate), which featured a lower critical solution temperature (LCST) of 61 °C in water. Further, the reactivity of the copolymer was exemplary proven by complete reacti…

Interfacial stabilization by soft Janus nanoparticles

2016

Abstract The stabilization of water/air, water/oil and water/solid interfaces by Janus particles with polystyrene (PS) and poly(methacrylic acid) (PMAA) hemispheres was systematically investigated. The stabilization of these interfaces is of relevance for the formulation of foams, emulsions and dispersions. The Janus particles were prepared from micellar solutions of polystyrene-b-polyisoprene-b-poly(tert-butyl methacrylate) (PS-PI-PtBMA) triblock terpolymers by selective cross-linking of the polyisoprene domain on a multi-gram scale, followed by hydrolysis of the PtBMA block. For the investigation of water/oil-emulsions a series of hydrophobic oils (paraffin oil, xylene, peanut oil, isopro…