Phase Segregation of Thin Film Polymer Blends on Au Nanopatterned Si Substrates

AFM study of phase-separated morphology in immiscible blend thin films

Phase-separation behavior of polystyrene (PS) and poly(methyl methacrylate) (PMMA) 1:1 blend film has been studied as a function of film thickness and component by adding PS-b-PMMA diblock copolymer. After annealing, PS is phase-separated into circular-shaped bumps on a PMMA layer. The bump number is inversely proportional to the film thickness in log-log plot while the slope is invariable for the blends with and without 5% PS-b-PMMA diblock copolymer. The bump size and inter-bump spacing are also affected by both the film thickness and addition of the block copolymer.

Carbon-13 Labeled Polymers: An Alternative Tracer for Depth Profiling of Polymer Films and Multilayers Using Secondary Ion Mass Spectrometry

13C labeling is introduced as a tracer for depth profiling of polymer films and multilayers using secondary ion mass spectrometry (SIMS). Deuterium substitution has traditionally been used in depth profiling of polymers but can affect the phase behavior of the polymer constituents with reported changes in both bulk-phase behavior and surface and interfacial interactions. SIMS can provide contrast by examining various functional groups, chemical moieties, or isotopic labels. 13C-Labeled PS (13C-PS) and unlabeled PS (12C-PS) and PMMA were synthesized using atom-transfer radical polymerization and assembled in several model thin-film systems. Depth profiles were recorded using a Cameca IMS-6f magnetic sector mass spectrometer using both 6.0-keV impact energy Cs+ and 5.5-keV impact energy O2+ primary ion bombardment with detection of negative and positive secondary ions, respectively. Although complete separation of 12C1H from 13C is achieved using both primary ion species, 6.0-keV Cs+ clearly shows improved detection sensitivity and signal-to-noise ratio for detection of 12C, 12C1H, and 13C secondary ions. The use of Cs+ primary ion bombardment results in somewhat anomalous, nonmonotonic changes in the 12C, 12C1H, and 13C secondary ion yields through the PS/PMMA interface; however, it is shown that this behavior is not due to sample charging. Through normalization of the 13C secondary ion yield to the total C (12C + 13C) ion yield, the observed effects through the PS/PMMA interface can be greatly minimized, thereby significantly improving analysis of polymer films and multilayers using SIMS. Mass spectra of 13C-PS and 12C-PS were also analyzed using a PHI TRIFT I time-of-flight mass spectrometer, with 15-keV Ga+ primary ion bombardment and detection of positive secondary ions. The (12)C7(1)H7 ion fragment and its 13C-enriched analogues have significant secondary ion yields with negligible mass interferences, providing an early indication of the potential for future use of this technique for cluster probe depth profiling of high molecular weight 13C-labeled fragments.