Plastic pollution is a defining problem of our time. Thus, it is crucial to design degradable polymers as replacements of conventional polymers that persist in the environment for centuries. However, a challenge with degradable polymers is unintentional scission of degradable linkages, resulting in undesirable loss of properties during storage or use. We report a strategy to combine thermal and photo-stimuli as a dual trigger “AND” gate enabling the creation of a stable thermoset with triggered spatiotemporal control of degradation. Thioether networks are synthesized using commercial thiol and bisallyl benzylidene acetal monomers in a one-pot two-step process with 5% excess thiol. First, the excess thiol is thermally protected, resulting in a stoichiometric thiol-ene resin which is subsequently photocured in the presence of photoinitiator. In the absence of any protecting group, thermosets readily degrade under UV irradiation with thiyl radicals from excess thiols acting as polarity reversal catalysts to abstract the acetal proton and affect cataclysmic degradation of acyclic benzylidene acetals to benzoate esters within seconds, as previously reported by our research group. The presence of a thermal protecting group prevents photolysis of the benzylidene acetal in ambient conditions. However, the network readily degrades within a few minutes when subjected to a dual thermal and photo-trigger. Thermolysis of the protecting group was explored further to alter the rates of network degradation. Thermal deprotection rates were quantified via variable temperature NMR experiments to ascertain activation energy by modulating electronic effects and catalyst loading.

Command construct/destruct thermosets using light and heat as "and" gate triggers

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