Cryo Atomic Force Microscopy: A New Way to Investigate Elastomeric Samples

Full text: The sectioning of samples at low temperatures down to -190oC is known as cryoultramicrotomy. Combined with an atomic force microscope (AFM) operating at the same temperature this is a new method that offers great possibilities to investigate soft materials, e.g. polymers. We are encouraged to share the results of AFM measurements, done at room temperature and under cryo conditions, to point out new opportunities in material characterization. One crucial influence on the quality of measurements is sample preparation by ultramicrotomy. Since we use elastomers, ultramicrotomy has to be operated under cryo conditions due to the fact that soft polymers usually have a glass transition temperature significantly below 00C and most elastomers and their composites can only be sectioned at temperatures 10 to 20 degrees lower than their glass transition temperature. By comparing block faces after sectioning, done at room temperature and under cryo conditions it is easy to see how the quality of the surfaces and therefore the AFM image quality is improved. Preparation of a sample with the ultramicrotome and measuring the bulk surface right after, both under cryo conditions, lead to new observations. Measuring at room temperature would imply heating up of the sample and therefore changes in the internal structure. It is now the first time that we are able to observe polymers in the cryo state and prevent the samples from changes between sectioning and measuring. We would like to discuss these results by looking at experiments done using different elastomeric polymer blends. (author)