Morphological transformation of [60]fullerene-containing poly(acrylic acid) induced by the binding of surfactant.
Water-soluble pH-responsive [60]fullerene end-capped poly(acrylic acid) (PAA85-b-C60) was synthesized using atom-transfer radical polymerization (ATRP) technique. The unusual morphological transformation of the polymer induced by the binding of nonionic surfactant Triton X-100 (TX100) at different degrees of neutralization (alpha) was investigated using isothermal titration calorimetry (ITC), UV-vis spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). For the 5 mM (monomer concentration) polymer solution at pH < 4, approximately 1.3 mM TX100 binds specifically to C60 domains of the polymeric micelles driven by hydrophobic interaction, which induces a structural transformation of the polymer from a large compound micelle with a radius of 110 nm to a dense precipitated spherical polymer/surfactant complex (PSC) with a radius of 500 nm. The precipitates are resolubilized by a wetting layer of TX100 in excess surfactant (> 1.7 mM in the polymer solution). The binding is significantly weakened and the complexation is disrupted with increasing pH, where the interaction completely ceased at pH > 6.
Wang
Chang
C
Singapore-MIT Alliance, School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore.
Ravi
Palaniswamy
P
Tam
Kam Chiu
KC
D000180:Acrylic Resins / Q000737:chemistry*; D037741:Fullerenes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008823:Micelles; D017830:Octoxynol / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*
D000180:Acrylic Resins; D037741:Fullerenes; D008823:Micelles; D013501:Surface-Active Agents; C006903:carbopol 940; D017830:Octoxynol