e-Polymers 2005, no. 075. ISSN 1618-7229 http://www.e-polymers.org Surface functionalization by smart binary polymer brushes to tune physico-chemical characteristics at biointerfaces Petra Uhlmann 1 , Nikolay Houbenov 1 , Sergiy Minko 2 , Manfred Stamm 1 1 Leibniz-Institute of Polymer Research, Hohe Straße 6, 01069 Dresden, Germany; Fax +49 351 4658 281; uhlmannp@ipfdd.de 2 Clarkson University, Department of Chemistry, Potsdam, New York 13699-5810, USA; Fax 315 268 2389; sminko@clarkson.edu (Received: September 23, 2004; published: October 28, 2005) This work has been presented at the E-MRS Fall Meeting, September 6 - 10, 2004, in Warsaw, Poland Abstract: Polymer brushes consist of an assembly of polymer chains that are attached by one end to the surface with sufficient grafting density. Binary brushes constituted from two incompatible polymers can be used in the form of ultrathin polymeric layers as a versatile tool for surface engineering to tune physico- chemical surface characteristics as wettability, surface charge, chemical compo- sition or morphology, and furthermore to create responsive surface properties. It is also possible to fix surface structures obtained in this way by (photo)crosslinking of the layers. Mixed brushes of oppositely charged polyelectrolytes are representing a special case of responding surfaces, which are sensitive to changes of the pH in aqueous environment. It is shown that structural changes occur in the plateau region of the adsorption isotherm of a model protein and that changes of the pH also cause changes in the structure of the adsorbed protein layer. Introduction A very promising means to optimize surface properties is the deposition of thin polymeric layers. Grafting techniques where the polymer is covalently linked to the surface have several advantages, as easy and controllable introduction of polymer chains with high surface density, precise localization of the chain at the surface, the possibility to graft different polymers on the same substrate, and last but not least long-time stability of the grafted layers. The term ‘brush’ means in this context a dense layer of chain-like polymers with one end fixed on a substrate and the mean grafting distance shorter than the mean size of the polymers [1]. When grafting two (or more) incompatible polymers, the anchoring of the polymer chains prevents macroscopic separation of the system; this allow creating surface properties that on one hand combine the properties of the grafted polymers and on the other hand allow switching of the surface characteristics. Therefore, mixed polymer brushes, created from two or more polymers, represent polymer systems with remarkable responsive properties to external fields. Phase 1 - 10.1515/epoly.2005.5.1.794 Downloaded from PubFactory at 09/02/2016 09:29:39AM via free access