Harnessing entropy to direct the bonding/debonding of polymer systems based on reversible chemistry

Abstract

The widely accepted approach for controlling polymer debonding/rebonding properties in responsive materials has been to purposefully engineer the functional end-groups responsible for monomer dynamic bonding. Here, however, we evidence that the debonding temperature of a polymer can also be tuned by changing the chain length of the polymer building blocks, thus altering the entropy released on debonding. Entropy driven debonding, as governed by building block chain length, is suggested theoretically and realized experimentally for two Diels–Alder polymer systems, each based on a different difunctional diene and a common difunctional dienophile. In each case a significant decrease (as much as 60 °C) in the retro Diels–Alder temperature was observed when the chain length of the difunctional dienophile building block was increased. These results have the potential to fundamentally change the approach utilized to design materials capable of bonding reversibly on demand.