Surface Coatings Based on Polysilsesquioxanes: Grafting-from Approach Starting from Organic Polymers
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1190-NN10-02
Surface Coatings Based on Polysilsesquioxanes: Grafting-from Approach Starting from Organic Polymers Daniel Kessler and Patrick Theato Institute of Organic Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55099 Mainz
ABSTRACT Poly(methylsilsesquioxane) (PMSSQ) based hybrid materials are promising candidates to produce substrate-independent stable and adherent surface coatings. Usually these materials are synthesized by controlled radical polymerization from inorganic precursors. The presented synthetic pathway in here demonstrates how to graft PMSSQ networks from an endgroupfunctionalized organic polymer and thus enlarges the range of accessible inorganic/organic hybrid coating materials. INTRODUCTION The quality of adhesion between solids, e.g. between a film and its substrate, depends to a large extent on the microstructure of the interface layer that is being formed [1]. Usually four types of interface layers can be formed during the coating process of polymers onto different substrates: 1. mechanically interlocked interfaces; 2. chemical bonding interface layers; 3. electric double layers; 4. diffusion interface layers [2,3]. Many different approaches have been explored recently to coat various substrates with polymers for various applications: The technique of grafting polymers from or onto surfaces [46] relies on chemical bonding interface layers and therefore depends on corresponding functional groups on the surface. Sol-Gel based coatings require free hydroxyl groups on the surface to form chemical bonds. For example on glass, silicon or metals hydroxyl groups are usually present [7], while on other substrates an additional plasma procedure may be necessary [8]. Polymer coatings on plastic substrates adhere due to a diffusion interface layer, if the polymers are miscible [9], requiring fine tuning between film and surface material. Electric double layer interfaces were formed in polyelectrolyte coatings [10]. Cross-linkable random copolymers as coating materials [11] exhibit a mechanically interlocked interface on rough surfaces. After cross-linking the former substrate topography is filled with rigid and stable polymer networks. The disadvantage of almost all reported procedures is their limitation towards the natured substrate to be coated, which is due to the utilization of only one interface layer phenomenon to guarantee adhesion. Recently, we introduced inorganic/organic hybrid polymers, consisting of poly(methylsilsesquioxane) (PMSSQ) and radically polymerized organic polymers [12,13]. After curing, stable and adherent films on various substrates have been achieved. On hydroxylated surfaces chemical bonding interfaces causes adherence, on polymeric substrates diffusion interfaces improve adherence and due to cross-linking of the PMSSQ moieties rigid polymer networks at the interface create mechanical interlocking.
Usually those hybrid polymers were synthesized in a controlled radical polymerization of the organic monomer from a PMSSQ precursor (ATRP in ref.[12] and RA
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