81 research outputs found

    New insight into the mechanism of the reaction between a,b-unsaturated carbonyl compounds and triethylborane (Brown's Reaction),

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    A study of the reaction of alpha,beta-unsaturated carbonyl compounds with triethylborane under free radical conditions (Brown's reaction) including spectroscopic analyses (B-11 NMR, IR, EPR) of products and intermediates indicated that these reactions involve the prior formation of an 'alpha,beta-unsaturated carbonyl compound-organoborane' complex. (C) 2000 Elsevier Science Ltd. All rights reserved.</p

    New insight into the mechanism of the reaction between a,b-unsaturated carbonyl compounds and triethylborane (Brown's Reaction),

    No full text
    A study of the reaction of alpha,beta-unsaturated carbonyl compounds with triethylborane under free radical conditions (Brown's reaction) including spectroscopic analyses (B-11 NMR, IR, EPR) of products and intermediates indicated that these reactions involve the prior formation of an 'alpha,beta-unsaturated carbonyl compound-organoborane' complex. (C) 2000 Elsevier Science Ltd. All rights reserved.</p

    Water-soluble stimuli-responsive vesicles from peptide-based diblock copolymers

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    Polypeptide secondary structure controls the dimensions of aggregates formed from a polybutadieneb-poly(L-glutamic acid) diblock copolymer after direct dissolution into water. The hydrodynamic radius (RH) of these aggregates (even at high NaCl concentrations) were found to correlate (see picture) with a transition from a compactly folded α-helical poly(L-glutamic acid) block at low pH to an extended random coil conformation at basic pH

    From supramolecular polymersomes to stimuli-responsive nano-capsules based on poly(diene-b-peptide) diblock copolymers

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    This paper discusses the self-assembly of block copolymers into vesicular morphology. After a brief state of art of the field, a system based on an amphiphilic poly(butadiene)- b-poly(-L-glutamic acid) (PB- b-PGA) diblock copolymer in aqueous solution is discussed in detail. The aggregation behavior of this block copolymer has been investigated by means of fluorescence spectroscopy, dynamic (DLS) and static (SLS) light scattering as well as transmission electron microscopy (TEM). The diblock copolymer was found to form well-defined vesicles in water. The size of these so-called polymersomes or peptosomes could be reversibly manipulated as a function of both pH and ion strength. Depending on the pH of the aqueous solution, the hydrodynamic radii of these vesicles were found to vary from 100 nm to 150 nm. By cross-linking the 1,2-vinyl double bonds present in the polybutadiene block, the ability to transform a transient supramolecular self-organized aggregate into a permanent "shape-persistent stimuli-responsive nanoparticle" has been demonstrated
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