Preparation and analysis of switchable copolymers for biomedical application

Switchable polymer coatings can be prepared on a wide variety of biomaterials. To implement a particular switching effect, a stimuli-responsive layer is attached to the surface. Its molecular structure introduces the desired physicochemical mechanism, hi case of copolymers (also polymer blends, mixed brushes, etc.), the stimuli-responsive unit can be combined with a second unit that allows to set other material properties in a particular way. 

When the material of a switchable coaling is dissolvable in aqueous environments after phase transition, an effective anchorage mechanism toward the surface is essential. For that purpose, different routes that use the second, non-switching, comonomer unit were proposed. 

a reactive comonomer unit can be introduced for a direct covalent immobilisation. When the material surface to be coated contains hydroxyl groups (e.g., glass, silicon, titanium alloys), the silyl-hydroxyl reaction can be used. Following this route, Yang et al. (2010) combine A-isopropyl acrylamide (NiPAAm) with a 3(trimethoxysi-lyOpropyl methacrylate unit to provide a stable thermo-responsive cell culture surface on glass carriers. On an amine-modified surface, a randomly distributed copolymer of 

Switchable and Responsive Surfaces and Materials for Biomedical Applications 

NiPAAm and 10% acrylic acid was immobilised as reported by Lee and von Recum (2010). However, a prior activation of the acid groups by carbodiimide is required. In case of an epoxy functionalised substrate, carboxyl-containing comonomer units can be used for immobilisation directly. This was demonstrated by Kaufmann et al. (2010) for NiPAAm-based carboxyalkylacrylamide copolymers that bind to the substrate upon heat treatment at 170 °C. 

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Preparation and analysis of switchable copolymers for biomedical application... 

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