SURFACE-ENHANCED RAMAN-SCATTERING FROM POLYIMIDE MODEL COMPOUNDS ON FUNCTIONALIZED METAL-SURFACES .1. PHTHALIC-ANHYDRIDE 4-AMINOPHENYLDISULFIDE GOLD

The interphase between a polyimide and a metal substrate was modeled b y depositing phthalic anhydride (PA) onto a gold substrate pretreated with 4-aminophenyldisulfide (APDS) and then curing in a mixture of ace tic anhydride and pyridine or triethylamine. Surface-enhanced Raman sc attering (SERS) and reflection-absorption infrared spectroscopy (PAIR) were used to characterize the model interphases. It was found that AP DS was adsorbed dissociatively onto Au substrates through the sulfur a toms. The average tilt angle for APDS molecules adsorbed onto gold sub strates was determined, using RAIR, to be approximately 46 degrees. Ho wever, there was no preferred rotational angle of the adsorbed APDS mo lecules about the long molecular axes. When PA was deposited onto APDS -primed Au substrates, anhydride groups of PA reacted with amino group s of APDS to form amic acids. Curing these thin amic acid films in ace tic anhydride catalyzed with pyridine produced mainly isoimide species , while curing in the presence of triethylamine gave imide as the majo r product. The relative amount of isoimide and imide thus depended str ongly on the catalyst used in the chemical curing processes.