Polymers with Multiple Hydrogen-Bonded End Groups and Their Blends.
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 2,7-diamido-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 Tg, and then quenched, and their structures were analyzed by transmission electron microscopy (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.