One-Pot Synthesis of (E)-2-(3-Oxoindolin-2-ylidene)-2-arylacetonitriles

A highly efficient and expeditious one-pot approach towards 2-(3-oxoindolin-2-yl)acetonitriles was designed, which involves a base-assisted aldol reaction of ortho-nitroacetophenones, followed by hydrocyanation, triggering an unusual reductive cyclization reaction.     

Distribution of molar mass and branching index of natural rubber from hevea brasiliensis trees of different age by size exclusion chromatography coupled with online viscometry

Natural rubber from hevea brasiliensis trees (Thailand, RRIM 600 clone) of different age (8, 20, and 35 years) were characterized by size exclusion chromatography (SEC) coupled with online viscometry with respect to their distribution of molar mass and branching index at a temperature of 70°C using cyclohexane as solvent. The natural rubber samples were purified by washing with an aqueous solution of sodium dodecylsulfate and subsequent saponification. With this procedure physical branching points caused by phospholipids, proteins and hydrophobic terminal units, mainly fatty acids, of the natural rubber (cis-1,4-polyisoprene) molecule, could be removed leading to completely soluble polymer samples. All samples investigated possess a very broad (10 to 50,000 kg/mol) and distinct bimodal molar mass distribution. With increasing age of the trees the peak area in the low molar mass region decreases favoring the peak area in the high molar mass region. By plotting the branching index as a function of the molar mass it could be shown that branching of the natural rubber increases with both, the molar mass and the age of the trees.     

ChemInform Abstract: Electronic Structure Calculations for the Ternary Intermetallic Compounds A2MX and AMX2 (A: Li; M: Rh,Pd, Ir,Pt; X: Al,Ga, In) Using Density‐Functional Theory.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Unimer Exchange Is not Necessary for Morphological Transitions in Polymerization-Induced Self-Assembly

Polymerization-induced self-assembly (PISA) has established itself as a powerful and straightforward method to produce polymeric nano-objects of various morphologies in (aqueous) solution. Generally, spheres are formed in the early stages of polymerization that may evolve to higher order morphologies (worms or vesicles), as the solvophobic block grows during polymerization. Hitherto, the mechanisms involved in these morphological transitions during PISA are still not well understood. Combining a systematic study of a representative PISA system with rheological measurements, we demonstrate that—unexpectedly—unimer exchange is not necessary to form higher order morphologies during radical RAFT-mediated PISA. Instead, in the investigated aqueous PISA, the monomer present in the polymerization medium is responsible for the morphological transitions, even though it slows down unimer exchange.     

Influence of crosslinking conditions on the phase behavior of a polyacrylate-based liquid-crystalline elastomer

The influence of crosslinking conditions (γ-radiation-induced and chemical crosslinking above and below the clearing point) on the phase behavior of a liquid-crystalline polyacrylate-based elastomer is shown and discussed. The network formation in samples γ-irradiated in the nematic phase results in an increase of the clearing point T_n-i which does not depend on the crosslinking density expressed as the ratio of weight-average molecular weight over number-average molecular weight between crosslinks M _w/M _c within a wide M _w/M _c range. The distorting action of the crosslinking agent at the same temperature leads to the opposite tendency in the change of T_n-i. Crosslinking in the isotropic phase shows a strong decrease in T_n-i.