Rational Utilization of Intermolecular Interactions: Enhancing the Mechanical Properties of Amorphous Glassy Polymer through Flexible Backbones

Intermolecular van der Waals (vdW) forces are ubiquitous and essential in polymers. However, their coupling with chemical rigidity makes it difficult to isolate their effects in polymers, resulting in a lack of understanding of how vdW influences macroscopic performance. Here, we exploited single and double bonds to modulate the rigidity of the molecular backbone without significantly altering vdW interactions, thereby decoupling the chemical rigidity and vdW interactions. Using this strategy, we prepared corresponding amorphous resins and conducted an in-depth investigation of their macroscopic properties and microdimer binding characteristics. The macroscopic experiments demonstrated that the resin with the flexible single bonds exhibited greater apparent rigidity compared with the resin with the chemically rigid double bonds. Theoretical calculations at the microscopic level indicate that the deformability of the flexible backbone allows for more stable binding within the resin under vdW forces, thereby enhancing the apparent performance of the resin. We proposed a concise and self-consistent theoretical model to link macroscopic and microscopic phenomena, successfully explaining the loss modulus and tensile yield. Moreover, we pointed out that the enhancement of the flexible backbone, according to the energy properties, renders this effect applicable to various intermolecular interactions not limited to vdW forces. The study not only underscores the significance of the flexible backbone in designing high-performance polymers but also offers a new perspective for understanding the relationship between microscopic intermolecular interactions and the macroscopic properties of polymers.