Anand Sundararaman

Reversible Restructuring of Aqueous Block Copolymer Assemblies through Stimulus-Induced Changes in Amphiphilicity

ABC triblock copolymers with a hydrophilic-thermomorphic-hydrophobic block sequence can assemble into distinct structures in water above and below the lower critical solution temperature for the thermomorphic block. Characterization of aqueous solutions of a representative poly(ethylene oxide)-block-poly(N-isopropylacrylamide)-block-polyisoprene copolymer by light scattering and transmission electron microscopy shows that small spherical micelles are formed at low temperatures and that large vesicles are favored at higher temperatures. The transformation from micelles to vesicles is reversible but slow, occurring over several weeks.

A comparative study of base-free arylcopper reagents for the transfer of aryl groups to boron halides

Abstract A comparative study on the reactivity and selectivity of arylcopper species in reactions with boron halides was performed. Mesitylcopper reacts with BX 3 (X=Cl, Br) in toluene at low temperature under highly selective formation of the monosubstituted boranes MesBX 2 . The dimesitylboranes Mes 2 BX are gradually formed with a twofold excess of the organocopper reagent at elevated temperature. In contrast, pentafluorophenylcopper shows a tendency for formation of B(C 6 F 5 ) 3 in reactions with BX 3 irrespective of the stoichiometry used, suggesting a strong impact of electronic factors on the selectivity of the aryl transfer reaction. New procedures for the synthesis of the pentafluorophenylboron halides C 6 F 5 BX 2 (X=Cl: 57%; X=Br: 62%) and of tris(pentafluorophenyl)borane (80%) and related mixed-substituted triarylboranes from the base-free isolable pentafluorophenylcopper precursor have been developed.

Synthesis and Photophysical Characterization of Boron-Modified Thiophene Polymers

The functionalization of oligo- and polythiophene derivatives with Lewis acidic boron moieties is reported. These new materials are of interest for device and sensor applications due to their unusual photophysical properties. Article not available.