Nanoparticles with a Bicontinuous Cubic Internal Structure Formed by Cationic and Non-ionic Surfactants and an Anionic Polyelectrolyte.

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Abstract

Nanoparticles with an internal structure have been prepared by dispersing
under dilute conditions poly(acrylic acid) with a polymerization degree n = 6000 (PAA6000)
together with a cationic surfactant hexadecyltrimethylammonium hydroxide (C16TAOH)
and the non-ionic surfactant penta(ethylene glycol) monododecyl ether (C12E5) in water.
The nanoparticles are formed at different mixing ratios in the corresponding two-phase
regions (liquid crystalline phase/dilute isotropic phase) of the C16TAPA6000 complex salt/
C12E5/water ternary phase diagram. The particles consist of polyacrylate PA6000
− polyions,
C16TA+ surfactant ions, and C12E5. Their internal ordering was identified by small-angle Xray
scattering (SAXS) to be either bicontinuous cubic with the Ia3d crystallographic space
group or normal hexagonal depending upon the amount of C12E5. The bicontinuous cubic
phase, to our knowledge never observed before in polyelectrolyte−surfactant particle
systems, was inferred by SAXS experiments. The data also showed that this structure is
thermoresponsive in a reversible manner. The bicontinuous cubic space group transforms
from Ia3d to Im3m as the temperature decreases from 25 to 15 °C. According to dynamic light scattering and electrophoretic
mobility measurements, the particles have a well-defined size (apparent hydrodynamic radii RH in the range of 88−140 nm) and
carry a positive net charge. The size of the nanoparticles is stable up to 1 month. The faceted nanoparticles are visualized by
cryogenic transmission electron microscopy that also reveals their coexistence with thread-like C12E5 micelles.

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Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Fysikalisk kemi
Originalspråkengelska
Sidor (från-till)16536-16546
TidskriftLangmuir
Volym28
Utgåva nummer48
StatusPublished - 2012
PublikationskategoriForskning
Peer review utfördJa