MALDI-TOF MS investigations to control and define the composition of surface modified polymers

Research project P 13962 MALDI-TOF MS investigation of surface modified polymers Robert SAF 24.01.2000 Within the last decade matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF- MS) has become a unique analytical tool for synthetic polymers. The method is employed to investigate various aspects important in polymer chemistry, even in cases where other analytical techniques fail. Within this project MALDI-TOF NIS will be used to investigate the composition of polymers modified at the surface. The surface modification of polymers has attracted increasing attention since excellent bulk properties can be combined with specific surface properties important for numerous applications (e.g., coating industry, medical implants). In the present project photochemical methods will be developed in order to attach functional groups onto the surface of technically important polymers. These methods have the advantage that projection techniques allow illumination - and thus modification - of selected areas of the polymer surface. This is a distinct contrast to other techniques of surface modification (e.g., corona discharges, gas flames or plasmas). MAIDI-TOF MS will be employed for the characterisation of the modified polymer surfaces. This is essential in order to determine how experimental parameters of the photomodification methods have to be varied to achieve a controlled and well defined composition of polymer surfaces. In a second step, chemical transformation reactions will be used to convert the photochernically introduced functional groups. Again MALDI-TOF MS results will be used for optimisation of the reaction conditions towards increased uniformity and selectivity. All investigations will be assisted by other analytical techniques (e.g., FTIR, SEC, XPS, EDX). The experiments will be focussed towards the introduction of acidic (e.g., -S03H, -COOH), basic (-NH2) as Well as neutral (-CN, -S02NHR) groups. The controlled introduction of such functional groups is a key for numerous applications. The MAIDI-TOF MS investigations are essential for both development and application of the surface modification methods under consideration. Furthermore, new techniques for the characterisation of the very top layers (some nm) of polymer films by MALDI-TOF MS will be explored. Special methods for the sample preparation for MALDI (e.g., spraying of suitable matrix solutions onto polymer surfaces) will be the central aspect of these experiments.

Within this project new photochemical methods for the modification of polymer surfaces and thin films were developed. These modification reactions have attracted increasing attention since excellent bulk properties can be combined with specific physical/chemical surface properties important for numerous applications (e.g., optical and electronic components, sensors, coating industry, medical implants). The new photochemical methods were successfully used to attach functional groups - e.g. amines, cyanides, thioles, trialkylsilanes - to technically important standard polymers (teflon, polystyrene) as well as to semi- conducting polymers. The photomodification of functional groups already present was possible too - an example is the reduction of double bonds. The methods have generally the advantage that projection techniques allow illumination - and thus modification - of selected areas of the polymer surface. This is a distinct contrast to other techniques of surface modification (e.g., corona discharges, gas flames or plasmas). Furthermore, the photochemically generated functional groups could be used as anchoring groups during post-chemical modification reactions. Various analytical techniques were successfully employed for the characterisation of the modified polymer surfaces. This was essential in order to determine how experimental parameters of the modification methods have to be varied to achieve a controlled and well defined composition of polymer surfaces - the key for subsequent applications. The new methods were already successfully used to alter the refractive index of polymer films, which renders the use in the field of optical applications possible, e.g. for optical waveguides. for the patterning of thin films of conjugated polymers. In this case the electronic properties were modified in order to produce multi-colour organic light emitting devices. to immobilize bio-molecules on polymer surfaces, which is of potential interest for biochip applications.