1,721,094 research outputs found
Glowing teacup demonstration: Trautz-schorigin reaction of natural polyphenols
No full textA safe, versatile demonstration of singlet oxygen chemiluminescence by means of Trautz-Schorigin reaction is described. Instead of toxic pyrogallol, green tea is used as a source of polyphenols. The effect of an antioxidant (ascorbic acid) and of boric acid on chemiluminescence is studied. This demonstration is suitable either for organic chemistry and general chemistry courses and can also be performed as an experiment by students
Core-shell functional nanospheres for oligonucleotide delivery. III. Stealth nanospheres
No full textPolymthyl methacrylate-based stealth and functional nanospheres, specifically designed for the reversible adsorption of oligonucleotides (ODN), were prepared by emulsion polymerization of methyl methacrylate in the presence of an ionic comonomer, namely a quaternary ammonium salt of 2-(dimethylamino)ethyl methacrylate, and a nonionic comonomer, namely a poly(ethylene glycol) methacrylate. The nanosphere size is substantially affected by the amount of both the nonionic and ionic comonomers. By appropriately adjusting the concentrations of the ionic and nonionic comonomers, the quaternary ammonium group and PEG chain surface densities can be finely tuned. Accordingly, a great variety of core-shell-type nanospheres, able to bind ODN and to induce dysopsonic effect, can be obtained
The "mushroom cloud" demonstration revisited
No full textA revisitation of the classical "mushroom cloud" demonstration is described. Instead of aniline and benzoyl peroxide, the proposed reaction involves household chemicals such as a-pinene (turpentine oil) and trichloroisocyanuric acid ("Trichlor") giving an impressive demonstration of oxidation and combustion reactions that can be useful either as part of a "chemistry show" or as a lecture demonstration for a general, inorganic, or organic chemistry course
Direct ESR detection of free radicals in the Raft polymerization of styrene
No full textBenzyl (diethoxyphosphoryl)dithioformate (1) has been used to control the AIBN initiated radical polymerization of styrene. In a comparative study with the more popular RAFT transfer agent benzyl dithiobenzoate (2), compound 1 led to higher molecular weight polymers, although with a slightly worse polydispersity. During the polymerization process mediated by 1 a few radicals have been intercepted and characterized by means of ESR spectroscopy. The nature and relative amount of the various radical species varied as the polymerization proceeded, matching expectations based on the generally accepted RAFT mechanism. The present ESR results induce a reassessment of the identity of a radical species observed in a previous preliminary study
Diblock and Triblock Functional Copolymers by Living Radical Polymerization
No full textControlled polystyrenes with different molar mass values were synthesized starting from benzoyl peroxide and TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxy). The polystyrene homopolymers served as initiators for the block copolymerization of phthalimide methylstyrene (PIMS) to synthesize polystyrene-b-poly(PIMS) diblock copolymers. Diblock copolymers with well defined structures as well as controlled and narrow molar mass distribution were obtained from the lower-mass polystyrene homopolymers. The lower-mass copolymers were found to Be active as initiators in the synthesis of the polystyrene-b-poly(PIMS)-b-polystyrene triblock copolymers, In each reaction step, the effects of conversion and reaction time on the molar mass characteristics of the prepared block copolymers were investigated. The diblock and triblock copolymers were modified using hydrazine as the reagent in order to obtain the corresponding functional amino block copolymers
Procedimento per la polimerizzazione radicalica vivente di monomeri olefinicamente insaturi
No full textComplex Associates of Plasmid DNA and a Novel Class of Block Copolymers with Poly(ethylene glycol) and Cationic Segments as New Vectors for Gene Delivery
No full textCationic block copolymers. consisting of a poly(ethylene glycol) block and a block deriving from the poly(dimethylamino)ethyl methacrylate were prepared via a two-step procedure, based on the use of macroinitiators. By appropriately changing the experimental conditions and reacting the poly(dimethylamino)ethyl methacrylate block with iodo- or bromo-alkyl derivatives, a variety of ionic block copolymers with tuned physicochemical properties were prepared. These block copolymers are able to spontaneously self-assemble with plasmid DNA to produce oriented and shielded vectors, with physicochemical properties appropriate for in vivo applications. In addition, the formation of a complex between the cationic block copolymer and the plasmid DNA results in a nuclease resistance increase due to the stable nature of the complex
Preparation and properties of PTFE/PAI nanocomposites
No full textPolytetrafluoroethylene/poly(amide-imide) PTFE/PAI nanocomposites were prepared by precipitation of TORLON® 4000TF (PAI) into a PTFE latex containing nanoparticles with average diameters of 41 nm and spherical shape. Several samples were obtained by varying the relative ratio between PAI and PTFE. SEM and PCS analysis indicates that the precipitation of PAI in the presence of PTFE leads mainly, if not exclusively, to bimodal mixtures of the two homoparticles. The PTFE crystallization process was quite complex and, depending on the sample composition, single or multiple crystallization exotherms were observed. This behavior, discussed within the fractionated crystallization frame, was revealing of the PTFE dispersion degree within the PAI matrix. When the PTFE amount is lower than 20%, a perfect PTFE nanoparticle dispersion is obtained. Partial aggregation is observed for PTFE amounts ranging from 20 to 40% whereas extensive aggregation is found for PTFE amount higher that 40%. The dynamic-mechanical behavior indicates that the interactions at nanoparticle/polymer interface are rather weak. A greater increase in the relative modulus (Ec/Em) in the rubbery state region with respect to the glassy region is observed and was explained in terms of the particle aggregation state
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