Towards the prediction and design of low-glass transition Donor-Acceptor semiconducting polymers

Past efforts on conjugated polymers, especially donor-acceptor (D-A) type polymers have mainly focused on the understanding of their structure-optoelectronic property relationship. However, the designing rule for fabricating soft and deformable semiconducting polymers is largely neglected. Here, we report a predictive linear model to quantitatively connect the glass transition behavior of D-A polymers to the flexibility of polymer chains, which is further verified through molecular dynamics simulation. The thermomechanical performance was characterized through pseudo-free-standing tensile test, thin film DMA and verified by AC-chip calorimetry. X-ray scattering and solution neutron scattering were applied to investigate the thin film morphology and polymer chain rigidity for further proof. This model shows its guidance role in molecular engineering of a low-glass transition pristine polymer with high mechanical deformability (~ 100%).