UV-curable acrylate metal oxide nanocomposite coatings

Abstract

Chapter 1 1.1. General introductionComposites are used when a combination of properties is required that cannot be found in a single material.Particularly interesting are combinations of organic polymers and inorganic materials as the properties of the pure components are very distinct.In general organic polymers are flexible, tough, and are easy to process, but they can also be relatively easily damaged, either chemically or mechanically.In contrast, inorganic materials are typically much harder, have better barrier properties, and have a good chemical stability, but are also brittle and are difficult to process.Organicinorganic composites may yield a combination of these properties, resulting in a hard, tough, and chemically stable and durable material that is still easy to process.However, the combination of organic and inorganic materials may also give a composite that is soft, brittle, unstable, and totally useless.The properties of a composite are not simply the average properties of its components.Besides the volume fractions of the components, also their size, shape, and the distribution are important.In a composite one component may be enclosed by another component that forms a continuous phase, but it is also possible that the components form continuous phases resulting in interpenetrating networks.Properties like heat conductivity and electrical conductivity are controlled by transport processes through one of the components; consequently a continuous network of the conducting component is highly advantageous.The interactions between the different components may induce changes in the chemical or physical structure of the components, especially in the first few nanometers from the interface (1)(2)(3) .These effects become particularly important when the interfacial area between the different components is large (3) .The interfacial area increases with decreasing domain size in the composite, and consequently also the properties may change by altering the domain size in a composite.For nanocomposites, with domain sizes of about 10 nm, 1 cm 3 of composite may contain several hundred square meters of interface, hence structural changes due to interface effects may affect a large portion of the material (3) .The addition of a third component that concentrates at the interface and alters the interactions can have strong effects on the composite properties (2)(3)(4)(5)(6) .The third component may be a surfactant that assembles at the interface by physical adsorption, or it may be a reactive species that is grafted on the surface of the filler or it may even react with both phases forming a chemical bond between the two phases (5) .This modification of the interface is often used to improve the mechanical properties of composites.MeO Si O OMe MeO O MeO Si OMe MeO 3-methacryloxypropyltrimethoxysilane (MPS) n-octyltrimethoxysilane (OTS) O O O O O n polyethyleneglycoldiacrylate (PEGDA) (mean n = 9) trimethylolpropyltriacrylate (TMPTA)