All-Atom Molecular Dynamics Simulations on a Single Chain of PET and PEV Polymers

Abstract

Polyethylene vanillic (PEV), a bio-based material, has mechanical and thermal properties similar to polyethylene terephthalate (PET), the most common polymer used in industries. The present study aimed to investigate and compare their structural dynamics and physical data using a computational approach. The simple model of a single-chain polymer containing 100 repeating units was performed by all-atom molecular dynamics (MD) simulations with refined OPLS–AA force field parameters. As a result, the flexibility of the PEV structure was greater than that of PET. PET and PEV polymers had the predicted glass transition temperature Tg values of approximately 345 K and 353 K, respectively. PEV showed a slightly higher Tg than PET, consistent with current experimental evidence.

Prediction of the Glass Transition Temperature in Polyethylene Terephthalate/Polyethylene Vanillate (PET/PEV) Blends: A Molecular Dynamics Study

“…The results in Figure 4 show T g values of 344–347 K for PET/PEV blends, in the same range for PEV (346 K) and PET (345 K), and which are close to the experimental [ 11 , 12 , 28 ] and computational [ 21 , 29 ] studies ( Table 2 ). The T g values for all PET/PEV ratios were not significantly different, unlike the PMMA/PS blends, which showed an increase in T g as the percentage of PS was enhanced [ 19 ].…”

“…The T g values for all PET/PEV ratios were not significantly different, unlike the PMMA/PS blends, which showed an increase in T g as the percentage of PS was enhanced [ 19 ]. Increased PEV chains in the simulation model in the present study slightly decreased the predicted T g value compared to the single-chain polymer [ 21 , 29 ]. This was not found in the case of PET.…”

“…The specific volumes of each PET/PEV blended system from the final simulation box length were plotted versus the temperatures from 100 K to 600 K relative to the PET and PEV ( Figure 4 ). The predicted T g of each system was the temperature at the intersection between the two trending lines that fitted from low temperatures of 100–300 K to high temperatures of 400–600 K. It should be noted that the T g prediction by monitoring the specific volume or density of a system per temperature has been used successfully in several polymers [ 13 , 14 , 20 , 21 , 26 , 27 ].…”

“…Every single chain of PET (T) and PEV (V) consisted of 100 optimized repeating units. Their atomic partial charges were taken from our previous study [ 21 ], while the parameters were based on the general force field OPLS-AA [ 22 , 23 ]. All five single chains of PET and/or PEV were first placed in parallel in a cubic box length of ~1500 Å.…”

“…One important key to defining the use of polymer is its glass transition temperature ( T g ) [ 13 , 14 ], which can be estimated and predicted by computational methods such as molecular dynamics (MD) simulation [ 15 , 16 , 17 , 18 , 19 ] via some thermodynamic properties such as the specific volume [ 13 , 19 , 20 ]. This study aimed to estimate the T g and evaluate some structural and dynamical properties of PET/PEV blends at different ratios using all-atom MD simulations with the force field parameters obtained from the previous study [ 21 ].…”