Complex coacervation core micelles as anti-fouling agents on silica and polystyrene surfaces

doi:10.1016/j.colsurfa.2004.04.068

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Volume 242, Issues 1–3, 2 August 2004, Pages 167-174

https://doi.org/10.1016/j.colsurfa.2004.04.068 Get rights and content

Abstract

The adsorption of mixtures of a diblock-co-polymer with a negatively charged block and a neutral, hydrophilic block and an oppositely charged homopolymer on anionic and hydrophobic surfaces was studied with reflectometry. It turned out that the adsorbed mass is at a maximum when the number of cationic and anionic polyelectrolyte groups is equal. In bulk solution, the components form micelles at this composition. The thickness of the layers was in the order of the micellar radius in bulk solution, i.e. 25 nm. The adsorption kinetics are sensitive to block lengths of the diblock-co-polymer. The adsorbed layers were stable with respect to solvent exposure and even 1 M ionic strength could not completely erode the layers. The layers dramatically influenced the functionality of the surface, as they acted as excellent anti-fouling agents versus protein adsorption.

Introduction

The formation of multilayers from oppositely charged polyelectrolytes on charged surfaces is an area of growing interest [1], [2], [3], [4], [5]. For applied aspects, one can think of e.g. surface modification [5] or enzyme immobilization [6]. Another method to modify surface functionality is by adsorbing a grafted polymer layer unto a surface [7].

In this paper, we present results on adsorption of oppositely charged (diblock-co)polymers on various surfaces. The components are (i) a diblock-copolymer with an anionic block and an water-soluble neutral block, and (ii), a cationic homopolymer. Under the right conditions, these components may form complex coacervation core micelles (CCCM’s). In Fig. 1, a CCCM is sketched schematically. In the present investigation, we do not supply the components in an alternating fashion as is the general procedure in the preparation of multilayers [8], [9], but the components are premixed first and then the surfaces are exposed to these mixtures.

In a previous paper [10], we have studied the properties of complex coacervation core micelles (CCCM’s) in solution. It was found that the CCCM’s form in a small compositional window around the composition where the number of cationic and anionic chargeable groups are present in approximately equal amounts. We call this composition the preferred micellar composition (PMC). Typical micellar hydrodynamic radii are around 15–30 nm. In reference [10], the aggregation mechanism of the CCCM’s is discussed in detail.

Firstly, we characterize the layers that are formed upon exposing various surfaces to a wide range of mixing ratio’s of the CCCM’s components. The results are discussed in terms of adsorption kinetics, adsorbed mass plateau values, and reversibility of the layer formation. Secondly, changes in surface functionality upon adsorbing CCCM’s on various surfaces are reported.

Section snippets

Materials

Light scattering (titration) experiments were described elsewhere [10]. For reflectometry experiments, we used silica in the form of silicon wafers (Wafernet GmbH, Germany) carrying an oxide layer of about 73 nm as determined by ellipsometry. The polystyrene coated wafers carried an oxide layer of about 41 nm, on top of which was a 66 nm polystyrene layer. A sol of silica particles with a radius of 95 nm was prepared in our own Laboratory according to the Stober method [11]. Before use, this silica

Characterization of the layers

In Fig. 2, we show plateau adsorption values as well as light scattering intensity data versus f_PAA, for mixtures of PVP with PAA₄₂PAM₉₇ and PAA₄₂PAM₄₁₇ respectively, on a silica surface. We see that at f_PAA=0.5, the intensity and adsorption are both at a maximum for both samples. For the light scattering intensity, this is in agreement with the results in previous work [10], where we have shown that for PAA/PVP the preferred micellar composition (PMC) is reached at roughly equal amounts of PAA

Conclusions

We have studied adsorption of complex coacervation core micelles on hydrophilic anionic surfaces (silica) and hydrophobic surfaces (polystyrene) with reflectometry and dynamic light scattering. The layer thickness on silica particles amounted to 25 nm, which is in line with the hydrodynamic radius of the micelles in bulk solution. The kinetics of adsorption were sensitive to variations in internal structure of the micelles. Micelles with a large core and thin corona adsorb much faster than

Acknowledgements

Wiebe de Vos is acknowledged for providing some of the experimental data. The authors thank Rhodia, Aubervilliers, France for financial support.

References (17)

A. Baba et al.
Colloids Surf. A
(2000)
N.G. Hoogeveen et al.
J. Colloid Interface Sci.
(1996)
J.C. Dijt et al.
J. Adv. Colloid Interface Sci.
(1994)
F. Caruso et al.
Science
(1998)
P.T. Hammond
Curr. Opin. Colloid Interface Sci.
(2000)
P. Bertrand et al.
Macromole. Rapid Commun.
(2000)
T.W. Graul et al.
Anal. Chem.
(1999)
F. Caruso et al.
Langmuir
(2000)

There are more references available in the full text version of this article.

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Complex coacervation core micelles as anti-fouling agents on silica and polystyrene surfaces

Abstract

Introduction

Section snippets

Materials

Characterization of the layers

Conclusions

Acknowledgements

Colloids Surf. A

J. Colloid Interface Sci.

J. Adv. Colloid Interface Sci.

Science

Curr. Opin. Colloid Interface Sci.

Macromole. Rapid Commun.

Anal. Chem.

Langmuir