A new strategy for synthesizing well-defined, chain-end-functionalized polymers containing multiple hydrogen-bonding (MHB) groups capable of heterodimerization in both solution and the melt has been developed. Two complementary MHB systems were chosen for initial studies: 2-ureido-4[1H]-pyrimidinone(UPy) and 2,7diamido- 1,8-naphthyridine (Napy) and ATRP initiators containing either UPy or Napy were prepared and shown to produce well-defined (meth)acrylic polymers with the desired MHB functionality present at the chain end. To characterize the effectiveness of the MHB interaction in the melt, blends of chain-end-functionalized linear polymers were cast into films, annealed at various temperatures above T-g, and then quenched, and their structures were analyzed by transmission electron micro scopy (TEM) and differential scanning calorimetry (DSC). It was shown that the nature of the hydrogen-bonding group(s) present in the blend has a significant effect on bulk microstructure and thermal behavior, in particular for blends of UPy- and Napy-functional chains.