Larry D. Unsworth, Zin Tun, Heather Sheardown, John L. Brash
Journal of Colloid and Interface Science 281 (2005) 112-121
Uns2005.htm
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Introduction
Notes by Dr. Zin Tun
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IntroductionPoly (ethylene oxide) (PEO)-modified surfaces have attracted much attention due to their excellent anti-biofouling properties [1-4]. In particular they have been shown to be resistant to nonspecific protein adsorption. An important class of such materials are formed by grafting, i.e., attachment of PEO to the surface via the polymer chain ends. Although the mechanism of protein resistance on these surfaces is not entirely clear, it is believed that the PEO chain length, surface chain density, and chain conformation are important factors [3,5]. -- (Uns2005intro01.gif)
Alexander [6] has pointed out that the conformation of end-tethered
chains on a surface depends on the chain density (Fig. 1). A random coil
conformation (mushroom regime) occurs when the graft spacing (S) is
greater than 2 RF (RF is the Flory radius),
and a more extended conformation (brush regime) occurs when S < 2 RF
. It is also well understood that stretching-entropy and excluded-volume
interactions influence the chain density in the brush regime, in both cases as a
result of lateral confinement. Thus by varying chain density,
chain conformation
ranging from unperturbed random coil to fully extended can, in principle, be
obtained. -- (Uns2005intro02.gif)
The focus of the present work is to produce well-characterized PEO-grafted surfaces of variable chain density and chain length to allow a detailed study of the influence of these parameters on protein resistance. In this article the preparation and characterization of a series of surfaces prepared by chemisorption of chain-end thiolated PEO (molecular weight range 750-5000) to gold is reported . Such a system should in principle allow variation of chain density up to high values, with an absolute upper limit corresponding to the density of thiol binding sites on gold. (Uns2005intro03.gif)
The coupling of polymers and other molecules to gold by reaction
with thiol groups has been widely reported [7-10]. A system that has been
investigated extensively consists of intermediate-length alkanes (e.g., C-11),
thiol-terminated at one end and "tipped" or not with an oligoethylene oxide (OEO)
moiety at the other end. In these systems the ratio of OEO-terminated to
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