Solvent-induced single-chain conformations of a linear synthetic polymer

In this study, we investigate the solvent-induced single-chain conformations of a model linear synthetic polymer using magnetic tweezers microscopy. We synthesize surface-grafted polynorbornene <i>in situ via</i> ring-opening metathesis polymerization and generate the single-chain elasticity profiles in different solvent environments by scanning the pulling force. The single-chain data demonstrate the sensitivity of the polymer conformations to the solvent, and the polymer undergoes a transition from a swollen chain behavior in toluene to a collapsed chain with increasing proportion of ethanol in the solvent mixture. Moreover, we observe hysteresis in the single-chain elasticity profiles in solvents containing a higher proportion of ethanol, suggesting that the chain may adapt different conformations under relaxation and stretching in poor solvents. Our results provide molecular-level fundamental insights into the mechanical behavior of synthetic polymers and their stimuli-induced conformations.