15 research outputs found
Self-assembled nanogel made of mannan : synthesis and characterization
Amphiphilic mannan (mannan-C16) was synthesized by the Michael addition of hydrophobic 1-hexadecanethiol (C16)
to hydroxyethyl methacrylated mannan (mannan-HEMA). Mannan-C16 formed nanosized aggregates in water by selfassembly
via the hydrophobic interaction among C16molecules as confirmed by hydrogen nuclearmagnetic resonance (1H
NMR), fluorescence spectroscopy, cryo-field emission scanning electron microscopy (cryo-FESEM), and dynamic light
scattering (DLS). The mannan-C16 critical aggregation concentration (cac), calculated by fluorescence spectroscopy with
Nile red and pyrene, ranged between 0.04 and 0.02mg/mL depending on the polymer degree of substitution ofC16 relative
to methacrylated groups. Cryo-FESEM micrographs revealed that mannan-C16 formed irregular spherical macromolecular
micelles, in this work designated as nanogels, with diameters ranging between 100 and 500 nm. The influence of the
polymer degree of substitution, DSHEMA andDSC16, on the nanogel size and zeta potential was studied byDLS at different
pH values and ionic strength and as a function of mannan-C16 and urea concentrations. Under all tested conditions, the
nanogel was negatively charged with a zeta potential close to zero. Mannan-C16 with higher DSHEMA and DSC16
values
formed larger nanogels andwere also less stable over a 6month storage period and at concentrations close to the cac.When
exposed to solutions of different pH and aggressive conditions of ionic strength and urea concentration, the size of
mannan-C16 varied to some extent but was always in the nanoscale range.International Iberian
Nanotechnology Laboratory (INL)Fundação para a Ciência e a Tecnologia (FCT