Molecular Origin of Efficient Phonon Transfer in Modulated Polymer Blends: Effect of Hydrogen Bonding on Polymer Coil Size and Assembled Microstructure

Molecular level engineering of polymer or polymer blends has been recently demonstrated an effective strategy to regulate thermal conductivity. Such materials are of great interest to meet critical requirements of transparent, lightweight, flexible, and so on for thermal management in electronic applications. In this work, modulated polymer blends with poly(vinyl alcohol) (PVA) and biopolymers (lignin, gelatin) were designed and significantly enhanced thermal conductivity was achieved by tuning the intermolecular interaction among polymer components. The hydrogen bond interaction has been revealed as the major driving force that affects the polymer coil dimension in aqueous solution, the microstructure of coil-coil interaction in solid film, and thus, the thermal conduction. A solid relationship across molecular level interaction to macroscale thermal conduction is constructed via careful characterization of the coil size in liquid phase and assembled microstructure in solid phase. Appropriate integration of biopolymers and PVA is essential to achieve synergistic effect. Specifically, thermal conductivity of polymer blend with 10% lignin and 10% G90 in PVA reaches 0.71 W/m.K, which is 184% enhancement as compared to pure PVA. This work reveals the fundamental molecular origin of polymer blends in association with thermal conductivity and has great potential to guide molecular engineering for superior physicochemical properties.