TIME-OF-FLIGHT SECONDARY-ION MASS-SPECTROMETRIC ANALYSIS OF POLYMER SURFACES AND ADDITIVES

This paper presents the application of static time-of-flight secondary ion mass spectrometry (ToF-SIMS) to the analysis of polymeric materia ls, including chemically modified polymers and polymer additives. Thro ugh the detection of intact functionalized oligomers, analysis of poly (styrene) functionalized with perfluoroalkyl chlorosilane provides con firmation of a successful endgroup termination for a living polymeriza tion. The calculated molecular weight distribution also is in good agr eement with chromatographic results. High mass resolution studies allo w monitoring of the hydrogenation of a poly(butadiene) polymer through increases in oligomer mass due to proton addition. The quantitative T oF-SIMS results for the extent of hydrogenation for a specific oligome r are lower than the values averaged over all oligomers as determined by magnetic resonance. The usefulness of ToF-SIMS for determination of trace-level polymer additives is demonstrated for linear low-density poly(ethylene) (LLDPE). Application of a 150 nm thick evaporated Ag pa ttern enables in situ detection of the five trace additives present in the LLDPE matrix, and also provides information on additive surface m igration and surface oxidation. A study of the silver cationization pr ocess for the silver-patterned LLDPE surface suggests differences in d iffusion and/or ionization processes for two additives. This is confir med with mass-resolved ion imaging to show the lateral distribution of the silver-cationized signals for various polymer additive molecular ions. Finally, poly(styrene) (M(n) = 1300) coated with a continuous si lver overlayer is investigated. The ToF-SIMS-determined molecular weig ht distribution shifts to lower masses, suggesting the greater diffusi on of shorter polymer chains through the silver overlayer.