MOLECULAR-WEIGHT DETERMINATION OF BULK POLYMER SURFACES BY STATIC SECONDARY-ION MASS-SPECTROMETRY

The determination of molecular weights at surfaces of bulk polymer mat erials can be accomplished by static secondary ion mass spectrometry ( SIMS) via fragments originating from repeat units and end groups. The intensity ratio of these fragments depends on the polymer chain length as seen for bisphenol-A-polycarbonate and perfluorinated polyethers ( Krytox), A kinetic model of fragment ion formation explains the molecu lar weight dependent fragment intensities and links them to properties of the molecular weight distribution. In the most simple case one obt ains the number average molecular weight <M-n> at the surface. This te chnique can be used for the determination of the molecular weight at b ulk polymer surfaces such as a CD-ROM made from polycarbonate by injec tion molding.