A novel maltoheptaose-based sugar ester having excellent emulsifying properties and optimization of its lipase-catalyzed synthesis.

A novel maltoheptaose-palmitate ester (G7-PA) was synthesized and investigated for emulsion properties. First of all, the optimal conditions for lipase-catalyzed G7-PA synthesis, which were 0.2 of the G7/PA molar ratio, 33.5 U of immobilized CALB per 1 g of PA in 10% DMSO, were determined by response surface methodology. G7-PA was compared with the commercial sucrose-PA (S-PA) in terms of emulsion-forming ability and stability at extreme conditions. At the 0.1% surfactant concentration, G7-PA emulsion exhibited a droplet distribution similar to the 0.2% surfactant condition, while S-PA emulsion was quickly destabilized. G7-PA showed better emulsifying properties than the S-PA at the acidic condition (pH 3). Flocculation and phase separation was observed at the S-PA emulsion, but the G7-PA emulsion was stable for 7-day. In thermostability tests, G7-PA and S-PA both were stable up to the boiling temperature. Conclusively, G7-PA exhibits excellent properties as a biosurfactant in O/W emulsion compared with S-PA.

Facile covalent attachment of well-defined poly(t-butyl acrylate) on carbon nanotubes via radical addition reaction.

We developed a new method to covalently attach well-defined polymers onto carbon nanotubes (CNTs) using a radical reaction. Well-defined poly(t-butyl acrylate) [p(tBA)] was first prepared by atom transfer radical polymerization, which formed radicals at the end of the polymer chain through an atom transfer. The generated radicals at the chain ends added CNTs to generate covalently functionalized p(tBA)-grafted CNTs. The polymer-attached CNTs showed much improved solubility in organic solvents. The synthesized MWNT-g-p(tBA) and SWNT-g-p(tBA) were characterized by IR, TGA and Raman spectroscopy, clearly indicating the formation of covalent bonding between p(tBA) and CNTs.