Polyelectrolyte Behavior of Diblock Copolymer Micelles Having Phosphonic Diacid Groups at the Corona
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- 作者：Vanessa Schmidt ; Emanuela Di Cola ; Cristiano Giacomelli ; Alain R. Brisson ; Theyencheri Narayanan ; Redouane Borsali
- 刊名：Macromolecules
- 出版年：2008
- 出版时间：March 25, 2008
- 年：2008
- 卷：41
- 期：6
- 页码：2195 - 2202
- 全文大小：537K
- 年卷期：v.41,no.6(March 25, 2008)
- ISSN：1520-5835
文摘
The polyelectrolyte behavior of block copolymer micelles originated from the self-assembly ofpoly(n-butyl acrylate)-block-poly((1-ethoxycarbonyl)vinylphosphonic diacid) (PBuA-b-PECVPD) chains wasstudied in detail by a combination of potentiometry, static and dynamic light scattering (SLS and DLS), small-angle X-ray scattering (SAXS), and cryo-transmission electron microscopy (cryo-TEM). In aqueous media, thehydrophilic PECVPD micelle corona bearing negatively charged phosphonic diacid groups [-P(O)(OH)2] withtwo distinct acid dissociation constants conferred interesting pH-, salt-, and concentration-dependent polyelectrolytefeatures to the system. Light scattering measurements showed the existence of three different regimes in the totalscattered intensity (Isc) and apparent hydrodynamic radius (RHapp) vs pH plots, reflecting the influence of theincrease in the negative charge density at the micellar corona due to deprotonation. The conformation andinteractions of polyelectrolyte chains were more strongly affected by salt addition for solutions with pH ~ 4.0.In such a case, the slope of KCp/I(q) vs q curves in SLS experiments changed from negative to positive valuesas the salt concentration (Cs) increased. During this transition, the variation of RHapp measured using DLS putforward the osmotic brush and salted brush regimes, the latter being characterized by a typical RHapp 
Cs-0.21scaling law. SAXS measurements revealed the core-shell structure and the electrostatic interactions between themicelles which decreased as expected upon the addition of salt. The analysis of the intensity profiles over a widerange of concentrations showed an inhomogeneous core-shell structure with the micelle shell thickness shrinkingin presence of added salt. Cryo-TEM images confirmed the spherical shape and narrow size distribution of themicellar nanoparticles.
Cs-0.21scaling law. SAXS measurements revealed the core-shell structure and the electrostatic interactions between themicelles which decreased as expected upon the addition of salt. The analysis of the intensity profiles over a widerange of concentrations showed an inhomogeneous core-shell structure with the micelle shell thickness shrinkingin presence of added salt. Cryo-TEM images confirmed the spherical shape and narrow size distribution of themicellar nanoparticles.