Coextruded sheets of PMMA and ABS are often used in furniture and sanitary industry to replace laquered parts in the furniture industry or cast acrylics in the sanitary industry. Compared to laquered surfaces the glossy PMMA materials generally suffer from poor cleanability and limited scratch resistance. The present master thesis deals with the surface modification of PMMA with the aim to develop covalently bonded coatings both to improve cleanability and scratch resistance. Coatings with reduced friction are seen as a way to achieve this goal. To ensure the chemical bonding of coatings on the polymer surface, a pre-treatment (activation) of the PMMA surface is required. Two different types of pre-treatments were investigated, corona activation and plasma discharges. Both processes are expected to provide the binding sites on the PMMA surface which is required for the covalent immobilization of functional coatings. To obtain durable coatings, two strategies were pursued: (i) the condensation of trialkoxysilanes with surface hydroxyl units at the activated PMMA, and (ii) a grafting reaction of vinyl-functional silanes at the PMMA surface. Graft reactions are essentially polymerization reactions which are initiated by free radicals at polymer surfaces. For the characterization of corona- and plasma activated surfaces and silane-coated specimens the contact-angle method was used, which provides information on variations of the surface tension. For a better understanding of the processes during the PMMA surface treatment also X-ray photoelectron spectroscopy and scanning electron microscopy were applied. To detect graft reactions at the surface, infrared spectroscopy (FTIR) was used as well. The investigations showed that PMMA surfaces are difficult to activate. Using corona and plasma reactions, comparably long reaction times under oxygen atmosphere are required. The coupling of trialkoxysilanes to activated PMMA surfaces was achieved by condensation reactions, but not by grafting processes.