The intimacy of component mixing in 2 blends of poly(4-hydroxystyrene) (PHS) and a photoacid generator (PAG), di(t-butylphenyl) iodonium perfluorooctane sulfonate (PFOS) were studied by solid state proton NMR. Mass ratios were 91/9 and 85/15 PHS/PFOS. These are simplified model blends for certain photoresist formulations used in the electronics industry. Multiple-pulse NMR techniques are used in both spin-diffusion and longitudinal relaxation experiments at ambient temperatures. It is deduced that PFOS is mixed with PHS on a molecular scale for PFOS mass fractions at or below 0.15; hence, the 2 components are thermodynamically miscible in this range. An attempt was also made to support the notion of intimate PFOS/PHS mixing by looking for evidence of 1H-19F dipolar broadening in multiple-pulse blend spectra. This attempt was not successful owing to rapid polarization-exchange between 19F nuclei.
Citation: Chemistry of Materials
Pub Type: Journals
iodonium sulfonate, miscibility, NMR, photoresist, poly(hydroxystyrene) photoacid generator, proton spin diffusion