A pH clock reaction is a reaction that has an abrupt change in pH at some point after the start of the reaction. In this work, we studied the bromate-sulfite-bisulfite pH clock reaction and the delay in clock time as a function of ammonium hydroxide. The bromate-sulfite-bisulfite clock reaction proceeds within minutes unperturbed. We observed an increase in clock time with an increase in ammonium hydroxide concentration. After the ammonium hydroxide has evaporated the clock reaction proceeds normally. We also observed that if the system is closed ammonia cannot evaporate, and the clock reaction will remain dormant until the system is opened and ammonia released. We studied the effect of storage time on clock time for varying concentrations of ammonium hydroxide.We also studied the possibility of coupling the clock reaction with the crosslinking of a poly(carbodiimide) via malonic and maleic acids, creating a programmable pH clock reaction triggered crosslinked coating.  The waterproof coating can easily be applied in single thins layers or multiple layers to create a thicker coating. When the pH of the clock reaction drops the environment becomes the ideal pH for the crosslinking to occur and in thin layers the ammonia evaporates very quickly; allowing the coating to form quickly. The polymer system also has an extended shelf life in the vial with ammonium hydroxide present to keep the pH high.

Development of time-lapse crosslinking triggered by the change in pH of a programmable pH clock reaction

247th National Meeting (2014)

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