Secondary interactions in polymers provide a unique platform to introduce directional and/or reversible intra- and inter-molecular interactions which improve thermomechanical properties and promote micro-phase morphology. Extensive studies focused on the structure-property relationship of one specific type of secondary interaction in polymers, such as hydrogen bonding and ionic interaction. However, current literature lacks fundamental understanding of block copolymers with multiple secondary interactions. Herein, we synthesized a series of ABA triblock copolymers with hydrogen bonding (urea) and ionic interactions (pyridinium) in the outer blocks. RAFT polymerization afforded the well-defined neutral triblock copolymers and post-polymerization quaternization of the side-chain pyridine allowed the synthesis of ABA triblock copolymers with both urea and pyridinium groups along the side chains. Upon quaternization, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) of the charged block copolymers evidenced an improvement of thermal stability and the appearance of crystalline domain. Wide angle X-ray scattering (WAXS) further confirmed the crystalline domain after quaternization. Variable temperature FTIR (VT-FTIR) revealed the different temperature responses of urea hydrogen bonding pre- and post-quaternization. Through the detailed study of these complex block copolymers, we observed, for the first time, crystallinity in block copolymers induced by quaternization.

Synthesis of block copolymers containing urea and pyridinium: A synergy of hydrogen bonding and ionic interactions

254th National Meeting (2017)

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