Conflicting role of plasticization in nanorheology of out-of-equilibrium thin polystyrene films

We have explored dewetting hole growth dynamics in high molecular weight polystyrene (PS) thin films plasticized by dioctyl phthalate (DOP). Addition of varying amounts of plasticizer reveals an interesting interplay with elasticity and viscosity beyond existing belief. While dewetting speed in plasticized films is enhanced via a possible decrease in viscosity of PS, its early stage thermal response leads to a scenario that can only be explained through enhanced molecular recoiling stress and interfacial friction or in other way, reduction in modulus in the plasticized film. While decoupling above effects is challenging, we have tentatively explained our observations on the possible roles of plastization, antiplasticization and nonequilibrium polymer chain conformations, perturbing nanorhelogy of such plasticized films.

Science and Engineering Research Board through Ramanujan Fellowship (Grant No. SB/S2/RJN-084/2018), and through Early Career Research Award (ECR/2018/001740) of Department of Science and Technology, India. IIT Bombay through a SEED Grant (RD/0519-IRCCSH0-033).