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The recording mechanism of a so-called CD-Recordable is reported; the disc consists of a pregrooved polycarbonate substrate, a dye, a metal reflector and an overcoat. After recording, bumps on the pregrooved substrate and pits at the dye/metal interface are observed. A method to determine the complex refractive index of a dye is explained and it will be shown how to obtain both a high reflection and a high modulation. From optical and thermal calculations and from recording experiments it is shown that two threshold temperatures are involved, associated with the softening of polycarbonate at 170°C and with a transition of the dye at 265°C.

Blends of poly (methyl methacrylate) (PMMA) with poly(vinylidene fluoride) (PVF2) are studied by fluorine-enhanced 13C solid-state nuclear magnetic resonance, while spinning at the magic angle (19F-13C CPMAS NMR). Data were acquired under simultaneous proton and fluorine dipolar decoupling. From these experiments it can be concluded that PMMA/PVF2 blends with weight ratios 80/20, 60/40, 40/60, and 20/80 are mixed at the molecular level. The average distance between PMMA C=0 and OCHa carbons and PVF2 fluorines in all blends is found to be between 2.6 and 3.1 Á.

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