Controlled anionic ring-opening polymerization of epsilon-caprolactone (epsilon-CL) in toluene using self-complementary quadruple hydrogen bonding array 2-ureido-4[1H]-pyrimidinone (UPy)-functionalized initiators with stannous(II) octanoate has been achieved to yield UPy-poly(epsilon-caprolactone) chains capable of undergoing supramolecular self-assembly. Molecular weights of these polymers varied from 2000 to 20 000 g/mol and were determined using H-1 NMR end-group analysis as well as gel permeation chromatography. Furthermore, using Ubbelohde solution viscometry, samples demonstrated a marked increase in viscosity-average molecular weight when measured in chloroform, indicating that the UPy chain ends are in a dimerized form when compared to polymer solutions in dimethylformamide (DMF).