J. T. Young

Determination of the Molecular Structure of Interphases Between Epoxy/4,4′-Diaminodiphenylsulfone Adhesives and Silver Substrates Using SERS and XPS

Abstract The molecular structure of interphases formed by curing an epoxy/4,4′-diaminodiphenylsulfone (DADPS) adhesive against rough silver substrates was determined using surface-enhanced Raman scattering (SERS) and x-ray photoelectron spectroscopy (XPS). SERS spectra obtained from the adhesive deposited onto silver island films were very similar to SERS spectra obtained from the DADPS curing agent spun onto silver island films, indicating that DADPS in the adhesive system segregated to the interphase and was preferentially adsorbed onto the silver substrate. Differences in the relative intensity of several bands in the normal Raman and SERS spectra of DADPS were observed. For example, the band near 1603 cm−1 was stronger in SERS spectra of DADPS than in normal Raman spectra. The band near 1150 cm−1 was weaker in SERS spectra of DADPS than in normal Raman spectra. These results implied that DADPS was adsorbed through one of the NH groups with an end-on conformation. Consistent results were also obtained ...

Molecular structure of interphases between DGEBA/BTDA adhesives and silver substrates using surface-enhanced Raman scattering

Abstract Surface-enhanced Raman scattering (SERS) was used for the non-destructive characterization of interphases between epoxy/anhydride adhesive systems and silver substrates. The normal raman spectrum of benzophenone tetracarboxylic dianhydride (BTDA) was characterized by strong bands near 1785 and 1860 cm−1 that were assigned to the anhydride groups, a strong band near 1690 cm−1 that was assigned to the benzophenone C─O stretching mode, and by a strong band near 1620 cm−1 that was attributed to vibration v(8b) of the benzene rings. The bands due to v(8b) and to the benzophenone C─O stretching mode were prominent in the SERS spectrum of BTDA but the bands related to the anhydride group were missing, indicating that the anhydride groups were hydrolyzed at the silver surface to form carboxylate groups. A band related to a CH out-of-plane bending mode which was absent from the normal Raman spectrum of BTDA was strong in the SERS spectrum, indicating that the molecules were adsorbed onto silver with a fla...

Surface-Enhanced Raman Scattering As an In-Situ Probe of Polyimide/Silver Interphases

Abstract The molecular structure of interphases formed by chemically curing the polyamic acid of pyromellitic dianhydride (PMDA) and oxydianiline (ODA) against meta-aminothiophenol (m-ATP)-primed silver substrates was determined using surface-enhanced Raman scattering (SERS) and reflection-absorption infrared spectroscopy (RAIR). It was found that m-ATP was adsorbed dissociatively onto silver substrates through the sulfur atoms. When polyamic acid was deposited onto silver substrates pretreated with m-ATP, acid groups of the polyamic acid combined with amino groups of m-ATP to form ammonium carboxylate salts near the interphase. SERS and RAIR results indicated that the structure of the interphase was significantly different from that of the bulk polymer. Chemical curing of the polyamic acids located in the interphase was suppressed because of the formation of ammonium carboxylate salts. However, the bulk of the polyamic acid films was highly cured to form polyimide. It was also found that more isoimide gr...

Surface-Enhanced Raman Scattering from Polyimide Model Compounds on Functionalized Metal Surfaces. Part II: Phthalic Anhydride/meta-Aminothiophenol/Silver

Abstract The interphase between a polyimide and a metal substrate was modeled by depositing phthalic anhydride (PA) onto a silver substrate pretreated with meta-aminothiophenol (m-ATP) and then curing in a mixture of acetic anhydride and pyridine or triethylamine. Surface-enhanced Raman scattering (SERS) and reflection-absorption infrared spectroscopy (RAIR) were used to determine the molecular structure of the interphase. It was found that m-ATP was adsorbed dissociatively onto silver substrates through the thiol groups. The tilt angle for m-ATP molecules adsorbed on silver substrates was determined using RAIR to be approximately 39°. However, there was no preferred rotational angle of the adsorbed APDS molecules about the molecular axes. When PA was deposited onto m-ATP pretreated silver substrates, anhydride groups of PA reacted with amino groups of m-ATP to form amic acids. When PA/m-ATP/Ag samples were chemically cured in acetic anhydride and pyridine or triethylamine, isoimide was the predominant pr...

Surface-Enhanced Raman Scattering from Polyimide Model Compounds on Functionalized Metal Surfaces. Part I: Phthalic Anhydride/4-Aminophenyldisul de/Gold

Abstract The interphase between a polyimide and a metal substrate was modeled by depositing phthalic anhydride (PA) onto a gold substrate pretreated with 4-aminophenyldisulfide (APDS) and then curing in a mixture of acetic anhydride and pyridine or triethylamine. Surface-enhanced Raman scattering (SERS) and reflection-absorption infrared spectroscopy (RAIR) were used to characterize the model interphases. It was found that APDS was adsorbed dissociatively onto Au substrates through the sulfur atoms. The average tilt angle for APDS molecules adsorbed onto gold substrates was determined, using RAIR, to be approximately 46°. However, there was no preferred rotational angle of the adsorbed APDS molecules about the long molecular axes. When PA was deposited onto APDS-primed Au substrates, anhydride groups of PA reacted with amino groups of APDS to form amic acids. Curing these thin amic acid films in acetic anhydride catalyzed with pyridine produced mainly isoimide species, while curing in the presence of trie...