We recently reported the cationic polymerization of o-phthalaldehyde to macrocyclic poly(phthalaldehyde) polymers. Resubjecting the cyclic polymers to the polymerization conditions led to a redistribution of the polymer to a new cyclic structure consistent with thermodynamic equilibrium. We now report the synthesis of cyclic poly(phthalaldehyde) derivatives and demonstrate the scrambling of distinct homopolymer mixtures to copolymers under the cationic polymerization conditions. Homopolymer mixtures are found to rapidly redistribute, first to multiblock cyclic copolymers. With extended reaction time, random macrocyclic copolymers are obtained. Evolution of the microstructure was monitored by NMR spectroscopy, MALDI-TOF mass spectrometry, and gel permeation chromatography (GPC). The reported scrambling method leads to the rapid preparation of macrocyclic copolymers of high molecular weight with variable microstructure depending on reaction times and catalyst loadings.