Acid catalysis films

N.F. Hu and J.F. Rusling, Electrochemistry and catalysis with myoglobin in hydrated poly(ester sulfonic acid) ionomer films. Langmuir 13, 4119-4125 (1997). 

The crosslinkers examined in this study were aminoplast resins 1-4 selected from melamine-formaldehyde, urea-formaldehyde, benzoguanamine-formaldehyde, and glycoluril-formaldehyde resins, all of which undergo the crosslinking sequence shown in Scheme 1. The response of these crosslinkers to acid catalysis in thin films is compared on a relative basis to the well studied methylated melamine, 1 19-11). 

These polymers are sensitive to thermolysis and decomposes rapidly and smoothly to bisphenol A, carbon dioxide, and volatile dienes when heated near 200 . For example polymer 8 affords only benzene, carbon dioxide, and bisphenol A upon heating. As in the case with t-butyl esters and carbonates, this thermolysis reaction is susceptible to acid catalysis and this property forms the basis of our resist design. The tertiary polycarbonate resist is formulated by casting a polymer film from a solution containing a few percent of substances which will produce strong acid upon photolysis. 

Recently, a new MF resin, tri(methoxymethyl)trimethylmelamine (TMMTMM), has been developed which has been found to be very useful in HS coatings. This has been shown to give faster curing and a unique combination of properties as compared to HMM, with a response to weak acid catalysis at a lower cure temperature (125 °C). The major drawback with this resin is that the cured films undergo decomposition under 60 °C Cleveland humidity conditions. Film decomposition has been assumed to be due to the higher basicity of TMMTMM, which promotes accelerated acid-catalyzed hydrolysis of the crosslinked sites. 

A widely used method of cross-linking paint films consists of reacting of hydroxyl containing acrylates or carbamate containing acrylates with melamine-formaldehyde resins or urea-formaldehyde resins [100-102]. Crosslinking is carried out at ca.l30 °C and is effected by acid catalysis (Fig. 7-5). The paints exhibit outstanding gloss and durability [103]. 

A number of metal porphyrins have been examined as electrocatalysts for H20 reduction to H2. Cobalt complexes of water soluble masri-tetrakis(7V-methylpyridinium-4-yl)porphyrin chloride, meso-tetrakis(4-pyridyl)porphyrin, and mam-tetrakis(A,A,A-trimethylamlinium-4-yl)porphyrin chloride have been shown to catalyze H2 production via controlled potential electrolysis at relatively low overpotential (—0.95 V vs. SCE at Hg pool in 0.1 M in fluoroacetic acid), with nearly 100% current efficiency.12 Since the electrode kinetics appeared to be dominated by porphyrin adsorption at the electrode surface, H2-evolution catalysts have been examined at Co-porphyrin films on electrode surfaces.13,14 These catalytic systems appeared to be limited by slow electron transfer or poor stability.13 However, CoTPP incorporated into a Nafion membrane coated on a Pt electrode shows high activity for H2 production, and the catalysis takes place at the theoretical potential of H+/H2.14... 

Gold forms a continuous series of solid solutions with palladium, and there is no evidence for the existence of a miscibility gap. Also, the catalytic properties of the component metals are very different, and for these reasons the Pd-Au alloys have been popular in studies of the electronic factor in catalysis. The well-known paper by Couper and Eley (127) remains the most clearly defined example of a correlation between catalytic activity and the filling of d-band vacancies. The apparent activation energy for the ortho-parahydrogen conversion over Pd-Au wires wras constant on Pd and the Pd-rich alloys, but increased abruptly at 60% Au, at which composition d-band vacancies were considered to be just filled. Subsequently, Eley, with various collaborators, has studied a number of other reactions over the same alloy wires, e.g., formic acid decomposition 128), CO oxidation 129), and N20 decomposition ISO). These results, and the extent to which they support the d-band theory, have been reviewed by Eley (1). We shall confine our attention here to the chemisorption of oxygen and the decomposition of formic acid, winch have been studied on Pd-Au alloy films. 

The drawback of the CVD method is eliminated in ROMP, which is based on a catalytic (e.g., molybdenum carbene catalyst) reaction, occurring in rather mild conditions (Scheme 2.3). A living ROMP reaction ofp-cyclophanc 3 or bicyclooctadiene 5 results in soluble precursors of PPV, polymers 4 [31] and 6 [32], respectively, with rather low polydispersity. In spite of all cis (for 4) and cis and trans (for 6) configuration, these polymers can be converted into aW-trans PPV by moderate heating under acid-base catalysis. However, the film-forming properties of ROMP precursors are usually rather poor, resulting in poor uniformity of the PPV films. 

The response of crosslinkers 1-4 to pTSA catalysis as a function of acid concentration is shown in Figure 2 for a 75°C/1 minute softbake and 105°C/1 minute hardbake cycle. The concentration of acid required to crosslink these films to a given LP is an indication of the relative resist sensitivities, while the steepness of the LP curves reflects resist contrast. Crosslinkers 3 and 4 are about twice as sensitive to pTSA catalysis as 1, while 2 requires a higher concentration of pTSA for crosslinking. Furthermore, the steepness of the curve for 3 suggests that it would show higher contrast in a resist formulation. 

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