The effects of plasticizers on the dynamics of polymer/plasticizer blends are practically important and theoretically interesting. Although it is well-known that plasticizers alter the glass transition of polymers, a microscopic view of the interplay between polymers and plasticizers and consequently the Tg shifts is not completely clear. In this work, we perform atomistic simulations on plasticized poly(vinyl chloride) (PVC) plasticized by varying concentrations of di(2-ethylhexyl) phthalate (DEHP). After validating the model by comparing simulated thermodynamic and mechanical properties with experimental values, we obtain both average and local Tg shifts from short-time segmental dynamics from data collapse. We find the average Tg determined from fast dynamics decreases substantially with increasing plasticizer concentration, consistent with volumetric Tg obtained from the temperature dependence of density. Furthermore, the local Tg reduction of PVC similarly obtained decays exponentially as a function of the distance from the nearest plasticizer molecule. Interestingly, the local Tg shifts seem to follow a simple additive rule, which can be described as the sum of the local Tg shifts in the dilute limit resulting from each plasticizer independently.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry