o-Benzyne was generated by oxidation of 1 -aminobenzotriazole derivatives covalently bound to various polystyrene supports. When lead tetraacetate is employed as the oxidizing agent, in the absence of any other substrates, the intermediate is converted to a mixture of isomeric aryl acetates. This reaction is not observed for monomeric 1 -aminobenzotriazoles, where dimerization is the predominant pathway. The results are explained by a low frequency of encounter between the polymerbound intermediates which allow the relatively slow acetate formation to compete with the encounter-controlled dimerization process. Delayed trapping of the intermediate by a diene demonstrated a surprisingly long lifetime for the intermediate. When iodobenzene diacetate was used as oxidizing agent, no acetates were formed, and a rather complex series of reactions eventually resulted in intrapolymeric coupling of the benzyne. From the delayed trapping experiments, conducted under these two different sets of conditions, it can be concluded that the frequency of encounter between the intermediates bound to a 2% crosslinked polystyrene resin must lie between 2.6 X 10~2 and 1.1 X 10-3 s-1.

Coalescence of a Maxwell viscoelastic sphere to a frictionless and flat rigid plane is analyzed to study the transition from initial elastic adhesion to viscous sintering. Deformation is driven by surface tractions due to the surface energy. The formulation for surface forces consistently combines direct van der Waals attraction across the gap ahead of the contact edge with curvature-based tractions normal to the sphere surface. These two contributions to the surface traction result in two different modes of contact growth. The initial elastic contact and the early stage of time-dependent contact growth are in a zipping mode of contact closure dominated by direct attractive forces. The later stage of sintering is by stretching of the contact and is dominated by curvature-based tractions. The transition from the initial elastic contact to the zipping mode of contact growth is viscoelastic. For a given sphere radius, kinetics of the zipping mode of contact growth scale with a characteristic viscous sintering time. However, this mode is not part of the existing sintering models because direct attractive tractions were neglected in previous analyses of sintering. This stage of coalescence does not have unique scaling with sphere radius. The transition from the zipping to stretching mode of contact growth occurs at a contact radius that depends on sphere radius. The stretching mode of contact growth is in good agreement with previous analyses of viscous sintering.

Polyimides derived from condensation of pyromellitic dianhydride with various diamines have been shown to be electrochemically active. Films of these materials coated on the surface of solid electrodes, immersed in electrolyte solutions of dipolar aprotie solvents undergo two distinct reversible redox processes, involving addition of one or two electrons per repeat unit. These processes can be carried out completely and stoichiometrically for films as thick as 20 ~m. Spectrophotometric studies and comparison with model compounds lead to the following conclusions: (i) ion permeability, which is a necessary component of the electrochemical charging and discharging processes, is related to solvent swelling and is, in turn, strongly influenced by the physical history of the polymer, (ii) redox activity involves localized molecular electronic states of the pyromellitic diimide group, (iii) there is no evidence for electronic interactions between pyromellitimide groups along a given polymer chain, and (iv) spectroscopic evidence indicates that weak interactions within the bulk of the polymer give rise to detectable inhomogeneities in optical or electrochemical properties of individual functional groups as a function of the charge on groups in their environment.

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