SYNOPSISMechanical and fracture mechanics properties of transparent multiphase epoxy resins toughened with various amounts of compatibilized silicone liquid rubbers consisting of polycaprolactone-block-poly ( dimethylsiloxane ) -block-polycaprolactone triblock copolymer have been investigated. At silicone liquid rubber contents < 10 wt % significantly improved toughness has been achieved without adversely affecting thermal and mechanical properties. Fractographic and interferometric methods have been applied to study crack propagation in such silicone-modified resins.

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The technique of transmission electron microscopy (TEM) in combination with electron spectroscopic imaging and digitized image processing was used for determination of particle size and size distribution of a starshaped polystyrene sample. The results were compared with measurements of the translational diffusion coefficient D, from dynamic light-scattering method. The particle diameter d,, achieved by TEM-measurements is in good agreement with the effective hydrodynamic radius R , from the Stokes-Einstein relationship.

Dedicated to Prof. Dr. H. Sinn on the occasion of his 6Sh birthday SUMMARY: Tailor-made segmented polymers play a key role in the development of novel polymeric materials exhibiting unsual bulk and surface properties. As a function of molecular architectures of segmented polymers, it is possible to control polymer morphologies and to achieve property synergisms. Selected examples are presented to illustrate basic concepts and recent developments. Segmented reactive liquid rubbers, containing an immiscible silicone segment flanked by two miscible oligo(capro1actone) segments, are efficient epoxy toughening agents. In such nano-phase-separated siliconemodiied IPNs impact strength is improved without sacrlfcing dimensional stability. Compatibilized blends of segmented phenolic polyurethane and nitrile liquid rubbers produce rubber blend microphases dispersed in epoxy prepregs which are used to bond aluminum sheets in strudural laminates. Reactive blending technologies are developed to produce segmented polymers as blend compatibilizers during melt processing, e.g., of polypropylendpolyamide 6 blends. Incorporation of oligo(tetrafluoroethene) segments into various condensation polymers modifies thermal and mechanical properties as well as surface tension and gas penneabilities.