The chemistry of corrosion resistant porphyrinic and porphyrinogenic materials.

摘要

Improvements in the protection of metals against corrosion has been a constant challenge to the paint and coatings. Electrically conductive polymers such as polyanilines or polythiopenes have shown the ability to retard corrosion through passivation of metallic surfaces which disrupts the electrochemical process of corrosion.; In particular, He and Gutherie have investigated the synthesis and use of porphyrinic and porphyrinogenic resins as corrosion resistant coatings. These resins are based upon the condensation of pyrrole and crotonaldehyde, pyrrole and cyclohexanone and 1-methylpyrrole and cyclohexanone. Modifiers such as butyl acrylate or acrylic acid are added to increase stability and to enhance coating properties such a flow, flexibility and storage stability of the resin. They propose that porphyrin and porphyrinogenic resin chemistry is based upon the following intermediates:*; Many of the resins tested provided good corrosion protection and even meso-tetraspirocyclohexylcalix[4]pyrrole itself showed efficacy as a corrosion inhibitor. One of the goals of this project was to determine the mechanism of resin curing and film formation in which we were unsuccessful. It was though that this process occurred either by polymerization of acrylate monomers in which porphyrinic or porphyrinogenic/calixpyrrole compounds were physically imbedded or that they actually reacted with the monomers to form part of the cured film.; Our results showed that pyrrole and crotonaldehyde based resins didn't seem to form any porphyrinic intermediates but did form polymers that gave good initial properties but were unstable in storage. However, investigation into the early stages of this reaction yielded the bicyclic compound shown below as a product that was unexpected based upon previous discussions and examples of this chemistry:*; Pyrrole and cyclohexanone resin formation involved the formation of the calixpyrrole/porphyrinogen meso-tetraspirocyclohexylcalix[4]pyrrole:*; In the case of 1-methylpyrrole and cyclohexanone resins, the compound 2,3,4,5-tetra(1-cyclohexen-1-yl)-1-methylpyrrole is the main product and not a classical calixpyrrole/porphyrinogen as might initially be expected:*; For both meso-tetraspirocyclohexylcalix[4]pyrrole and 2.3,4.5-tetra-(1-cyclohexen-1-yl)-1-methylpyrrole neither compound seems to react with any other resin components such as butyl acrylate or acrylic acid under the conditions of resin formation which is contrary to the chemistry proposed by He and Gutherie.; *Please refer to dissertation for diagrams.