Chain configurations in ordered symmetric poly(styrene-6-methyl methacrylate) diblock copolymers were examined by neutron reflectivity. In a thin-film geometry the copolymers organize into lamellar microdomains oriented parallel to the substrate surface. The copolymers were synthesized with small fractions of deuterated segments at either the chain ends or centers. This selective labeling permitted characterization of the spatial distribution of chain ends and junction points normal to the plane of the film. From the reflectivity analysis, the junction points are found to be confined to the PS/PMMA interfacial regions. The chain ends, however, are well distributed through their respective domains, exhibiting only a weak maximum in concentration at the center of the domains.
Quantitative determination of the molecular weight and composition of submicrogram quantities of a perfluorinated polyether (PFPE) supported on Ag and Si substrates was made from empirical relationships derived from the intensities of specific high-mass (>SO0 amu) fragmentation ions from time-of-flight secondary ion mass spectrometry (TOFSIMS) measurements. These relationships are explained in terms of simple concepts regarding the process of volatilization, fragmentation and ionization in TOFSIMS. The results for both negative and positive ions are nearly independent of the substrate materials used, demonstrating that the high-mass fragmentation ions in TOFSIMS may be useful generally for in situ quantitative analysis of PFPEs on non-specific substrates. This is an important difference between the TOFSIMS fragmentation spectrum and the complementary TOF-SIMS cationized molecular ion spectrum, which requires special sample preparation and/or substrates. In order to interpret the quantitative information available in the TOFSIMS fragment spectrum, it was absolutely necessary to characterize extensively the PFPE samples using NMR and TOFSIMS Ag'ationized molecular ion results.This characterization helped to demonstrate the power of TOFSIMS to do quantitative analysis and led to additional iasight concerning the SIMS ion-forming process for PFPE. This study represents one of the first attempts to make quantitative use of the high-mass fragment ion intensities in SIMS studies of polymers, and presents a method for confirming the origin of the mass peaks in the spectra.
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