Issue 29, 2012
From the journal:

Soft Matter

Synthesis and pH- and salinity-controlled self-assembly of novel amphiphilic block-gradient copolymers of styrene and acrylic acid†

O. Borisova,ab   L. Billon,*a   M. Zaremski,b   B. Grassl,a   Z. Bakaeva,c   A. Lapp,d   P. Stepanekc  and  O. Borisov*a  

* Corresponding authors

a UPPA, CNRS UMR 5254 IPREM Equipe de Physique et Chimie des Polymères, Pau, France
E-mail: oleg.borisov@univ-pau.fr, laurent.billon@univ-pau.fr

b Department of Polymer Science, Moscow State University, Leninskie Gory, Moscow 119191, Russia

c Institute of Macromolecular Chemistry AS CR, v.v.i., Heyrovského nám, 2, CZ-162 06 Praha 6, Czech Republic

d Laboratoire Leon Brillouin/LLB CNRS/CEA, Saclay, France

Abstract

A novel type of amphiphilic ionic copolymer comprising a hydrophilic poly(acrylic acid) (PAA) block and an amphiphilic poly(acrylic acid)-grad-poly(styrene) (PAA-grad-PS) copolymer block was synthesized using a one step direct nitroxide-mediated polymerization (NMP). A strong influence of the macroinitiator on the values of the reactivity ratios of the co-monomers is confirmed by 1H NMR. The aggregation behaviour of the copolymers in the aqueous medium was studied by small-angle neutron scattering (SANS) and dynamic light scattering (DLS) and by transmission electron microscopy (TEM) in a wide range of pHs and ionic strengths. It has been demonstrated that PAA-b-(PAA-grad-PS) copolymers are soluble in alkaline water at room temperature without the special experimental procedures (addition of co-solvent, heating, etc.) that are usually required for solubilisation of classical PAA-b-PS diblock copolymers. The self-assembly of the PAA-b-(PAA-grad-PS) copolymers into nano-scale aggregates at low/moderate pH and/or high ionic strength was demonstrated by SANS and DLS experiments. The SANS spectra for the copolymer solution exhibit a correlation peak pointing to the formation of micelles with repulsive coronae. TEM images indicate that the micelles have an approximately spherical shape and exhibit a wide size distribution. Our results prove, that in contrast to “frozen” aggregates formed by PAA-b-PS copolymers in aqueous media, the micelles of PAA-b-(PAA-grad-PS) amphiphilic copolymers exhibit “dynamic” pH-responsive properties, i.e. they can reversibly change their aggregation number upon a variation in the pH or salinity of the solution.

Graphical abstract: Synthesis and pH- and salinity-controlled self-assembly of novel amphiphilic block-gradient copolymers of styrene and acrylic acid

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Article information

DOI
https://doi.org/10.1039/C2SM25625H
Article type
Paper
Submitted
18 Mar 2012
Accepted
18 May 2012
First published
26 Jun 2012

Soft Matter, 2012,8, 7649-7659

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Synthesis and pH- and salinity-controlled self-assembly of novel amphiphilic block-gradient copolymers of styrene and acrylic acid

O. Borisova, L. Billon, M. Zaremski, B. Grassl, Z. Bakaeva, A. Lapp, P. Stepanek and O. Borisov, Soft Matter, 2012, 8, 7649 DOI: 10.1039/C2SM25625H

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