Aldehyde polymers have gained attention in recent decades as a class of stimuli-responsive materials capable of rapid, triggered depolymerization to monomer. Exploitation of the most prominent polyaldehydes for various solid-state applications, however, is limited by poor thermal and mechanical properties of the materials. To address these limitations, we pursued the copolymerization of ethyl glyoxylate, precursor to tacky polymers, with o-phthalaldehyde, precursor to brittle materials. Using NAIR spectroscopy and MALDI-TOF mass spectrometry, we have discovered the surprising tendency of these sequences to alternate, resulting in alternating cyclic copolymers in certain feed ratios. We also report the ability to tailor the thermal properties of the solid copolymers by varying copolymer composition, enabling the selective tuning of copolymer glass transition and degradation temperatures to meet application demands. We envision that this copolymer system, which blends the properties of the tacky and brittle homopolymers, will find use as depolymerizable polyaldehydes for solid-state applications.