The cure reaction pathways of a bismaleimide resin with a diamine are investigated using solid-state 15 N NMR spectroscopic techniques with specifically labeled monomers. These techniques provide clear identification of at least three different reaction pathways in the curing resin, one of which has previously been only postulated. In the homopolymerized bismaleimide resin system, maleimide ring addition has previously been shown to be the only observable reaction. When co-reacted with an amine, Michael addition of the amine to the maleimide ring has also been observed. Furthermore, a ring-opening aminolysis reaction, which has been observed in solution with specific reagents and conditions, has been suggested to occur under cure conditions. We show conclusively that this aminolysis reaction occurs to a significant extent during the cure of the neat resin and that this product can remain in the network structure even after a high-temperature postcure treatment. The existence of the amide product is demonstrated using bismaleimide resin formulations selectively labeled with 13 C and 15 N at specific sites. The 15 N chemical shifts and the 13 C-15 N scalar couplings are consistent with and confirm the amide product formation. Furthermore, under certain cure and postcure conditions, the aminolysis reaction is reversible which may significantly affect the final network structure.

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The effect of an ammonium sulfide treatment on the GaAs (100) surface has been investigated by x-ray photoelectron spectroscopy. The treatment produces a slight Ga enrichment on the surface and leaves roughly 0.6 of a monolayer of sulfide which inhibits initial oxidation of the surface. The sulfide is not lost as the surface becomes oxidized but appears to remain near the GaAs/oxide interface. Furthermore, in the oxidized layer, As oxide is preferentially drawn to the surface relative to Ga oxide.

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Copolymer networks of poly(methacrylic acid) (PMAA) and poly(ethylene glycol) (PEG) exhibit large changes in their swelling behavior over a narrow pH range due to the reversible formation/dissociation of interpolymer complexes between the polymer chains. Intepolymer complexation occurs in copolymer gels of PMAA and PEG due to hydrogen bonding between protonated acid groups and the ether groups of the PEG. Because of their nature, these gels have been identified for use as delivery vehicles for macromolecular drugs. In this work, solid‐state, nuclear magnetic resonance nuclear Overhauser enhancement (NOE) experiments were performed to detect the molecular level complexation between PMAA and deuterated PEG in copolymer blends and crosslinked networks. For gels swollen in acidic media at room temperature or at 37 °C, strong enhancements were detected in the 13C resonance of the PEG carbons. The NOE was generated due to energy transfer between the rapidly rotating methyl group protons and the deuterated PEG carbons. The presence of the NOE was indicative of close packing of the polymer chains and was evidence of the presence of the intermacromolecular complexes. In basic solutions, no NOE was detected in the PEG, as the complexes were dissociated and the chains were separated in space. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2823–2831, 2000