Search results for "Mono"

Reactive thiol-ene emulsion-templated porous polymers incorporating pentafluorophenyl acrylate

2013

Abstract Highly porous polymers (polyHIPEs) incorporating activated esters have been prepared by photopolymerisation of high internal phase emulsions (HIPEs) containing pentafluorophenyl acrylate (PFPA) in the monomer phase. The resulting materials have nominal porosity of 80% and a well-defined, interconnected pore morphology with average pore diameters ranging from 30 to 50 μm. PFPA could be added at up to 50 wt% of the monomer phase without destabilising the HIPE noticeably, however analysis of the polyHIPE materials revealed that only around half of this was incorporated into the final porous materials. The pentafluorophenyl groups were shown to be reactive towards a range of amines (tr…

Cyclodextrins in polymer synthesis: Influence of methylated β-cyclodextrin as host on the free radical copolymerization reactivity ratios of hydropho…

2001

Methylated (β-cyclodextrin (me-β-CD) was used to complex the hydrophobic monomers n-butyl acrylate (1), n-hexyl acrylate (2) and cyclohexyl acrylate (3) yielding the corresponding water soluble host/guest complexes 1a–3a. The complexes were copolymerized in water by free radical mechanism and the reactivity ratios were determined by measuring the monomer consumption by HPLC. The following reactivity ratios were found: copolymerization of 1a and 2a: r1= 1.01 ± 0.01; r2= 1.04 ± 0.01; copolymerization of 3a and 2a: r1= 0.74; r2= 1.28; copolymerization of 3a and 1a: r1= 0.75 ± 0.04; r2= 1.13 ± 0.01. In contrast to that, the copolymerization of the uncomplexed monomers 1–3 in organic medium (DMF…

Anionic Polymerization of (Meth)acrylates in the Presence of Tetraalkylammonium Halide−Trialkyl Aluminum Complexes in Toluene. 3. Kinetic Investigati…

2001

The polymerization of n-butyl acrylate initiated by ester enolates in the presence of tetraalkylammonium halide−trialkylaluminum complexes, R4N[AlnR‘3nX] (n = 1, 2), in toluene has a controlled character at −78 °C only for selected combinations of the complex. Quantitative monomer conversions are usually reached with Me4N[AlnBui3nCl] leading to polymers with narrow molecular weight distributions (Mw/Mn < 1.2). Kinetic investigations show a complex mechanism of the polymerization, implying an equilibrium between at least two active species. Besides, various acrylate homopolymers and block copolymers (PMMA-b-polyacrylate) can be synthesized with this new initiating system.

Identification and structural characterization of O-beta-ribosyl-(1"----2')-adenosine-5"-phosphate in yeast methionine initiator tRNA.

1990

We report in this paper on the complete structure determination of the modified nucleotide A*, now called Ar(p), that was previously identified in yeast methionine initiator tRNA as an isomeric form of O-ribosyl-adenosine bearing an additional phosphoryl-monoester group on its ribose2 moiety. By using the chemical procedure of periodate oxidation and subsequent beta-elimination with cyclohexylamine on mono- and dinucleotides containing Ar(p), we characterized the location of the phosphate group on the C-5" of the ribose2 moiety, and the linkage between the two riboses as a (1"----2')-glycosidic bond. Since the structural difference between phosphatase treated Ar(p) and authentic O-alpha-rib…

Monolayer Properties of Hydrophobic .alpha.-Helical Peptides Having Various End Groups at the Air/Water Interface

1994

Role of pH in the synthesis and growth of gold nanoparticles using L-asparagine: a combined experimental and simulation study

2020

Abstract The use of biomolecules as capping and reducing agents in the synthesis of metallic nanoparticles constitutes a promising framework to achieve desired functional properties with minimal toxicity. The system’s complexity and the large number of variables involved represent a challenge for theoretical and experimental investigations aiming at devising precise synthesis protocols. In this work, we use L-asparagine (Asn), an amino acid building block of large biomolecular systems, to synthesise gold nanoparticles (AuNPs) in aqueous solution at controlled pH. The use of Asn offers a primary system that allows us to understand the role of biomolecules in synthesising metallic nanoparticl…

Heat Capacity Study to Evidence the Interactions between Cyclodextrin and Surfactant in the Monomeric and Micellized States

2003

The heat capacities of transfer (ΔCpt) of hydroxypropyl-α-cyclodextrin and hydroxypropyl-γ-cyclodextrin (0.05 mol kg-1) from water to aqueous solutions of sodium hexanoate, sodium decanoate, and so...

Polymerization of Mono- and Bi-functional Diacetylene Derivatives in Monolayers at the Gas-Water Interface

1979

The spreading and polymerization behaviour of long chain acids and phospholipid analogues containing diacetylene groups is described. Especially the polymerization in monolayers is followed spectroscopically with a new device used in connection with a commercial UV spectrometer. The polymerization is topochemically controlled. Sonification of the phospholipid analogues in water results in the formation of liposomes with multilayered membranes. Polymerization of the liposomes in water forms aqueous solutions of polymer vesicles.

Alkaline Pre-treatment of Hardwood Chips Prior to Delignification

2013

Scots pine (Pinus sylvestris) chips were pre-treated with alkaline solutions (alkali charges of 1, 2, 3, 4, 6, and 8% of NaOH on the oven-dried wood material) at 130°C and 150°C for various treatment times (30, 60, 90, and 120 minutes). Under these conditions, 2.0–13.6% of the wood d.s. was dissolved into the aqueous hydrolysates. The soluble organic fraction was primarily characterized in terms of carbohydrates (monosaccharides and oligo-/polysaccharides) and their alkali-catalyzed degradation products: aliphatic carboxylic acids containing, besides non-volatile hydroxy carboxylic acids, volatile formic and acetic acids. With increasing alkali charge, temperature, and time, the enhanced fo…

Oscillatory dynamics of the Belousov-Zhabotinsky system in the presence of a self-assembling nonionic polymer. Role of the reactants concentration.

2010

In the present study, the role played by the reactants concentration on the nonlinear response of a Belousov–Zhabotinsky (BZ) system to the addition of a self-assembling non-ionic polymer, poly(ethylene glycol) (PEG), has been assessed. The oscillatory parameters are influenced to an extent that significantly depends on the concentration of both the polymer and the Belousov–Zhabotinsky components. The effects obtained were attributed to the reaction among some of the BZ key species and the backbone and the alcoholic functional groups of the polymer, both in its monomeric and aggregated forms. Support to the proposed perturbation mechanism has been provided by performing numerical simulation…