(255ak) Molecular Design of Bio-Based Plasticizers for PVC

There is growing concern for the toxicity of industrial polymer plasticizers to humans. Especially, phthalate derivatives are very common plasticizers and exhibit toxic effects by degradation. These plasticizers are particularly widely used in processing of polyvinyl chloride (PVC). In our study, various bio-based molecules with potential to replace phthalate derivative plasticizers for PVC have been modeled by employing atomistic scale simulations. Our approach depends on molecular dynamic simulations to determine polymer/plasticizer interactions and observe plasticization effects via the lowering of glass transition temperature (T_g). Structural stability was observed by solubility behavior of plasticizers in polymer and to describe T_g values and volumetric behavior of polymer/plasticizer mixtures, pressure-volume-temperature (PVT) relationship was used. Selected bio-based molecules including levulinic acid esters, succinic acid esters, oleate esters, dioctyl adipate and for comparison one of the phthalate derivative were constructed with TRAPPE-UA force-field, were optimized and their densities similar to literature were obtained Then, the atactic PVC homopolymer chains consisting of 150 monomers with equal fractions of meso- and racemic diads distributed randomly along the chain were constructed based on the Generalized Amber Force Field (GAFF), T_g and density of pure PVC was determined 344 K and 1.38±0.01 g/cm3. Polymer/plasticizer structures contained 10 to 30% plasticizer by weight to predict the performance of the plasticizers. Bio-based derivative esters, including levulinic acid esters and succinic acid, were also constructed with different chain length to observe chain length effect on plasticization. The variation of the polymer glass transition temperatures was investigated and compared as a function of plasticizer type and content by simulating PVT relationship and stability of the polymer/plasticizer mixtures were compared by calculated solubility values.

This work is part of the project supported by the Scientific and Technological Research Council of Turkey (TUBITAK) through the grant no. 114M178.