Computational determination of polymerization enthalpy of polylactide by employing DFT-B3LYP method
Project no. 21513 · Status: Kapanmış · 2020
Summary
Polylactide, which is popular due to its biodegradable and biocompatible properties, is used in areas such as tissue engineering, packaging, surgical thread, drug release. Thermodynamic properties of polymerization are important in understanding the effect of monomer structure on polymerization. Since entropy decreases during the polymerization reaction, the determining factor in the system's spontaneous or non-spontaneous progression will be polymerization enthalpy. It is known that polymerization enthalpy can be calculated from enthalpy values of oligomer structures containing consecutive numbered monomers. However, since the increase of these oligomer structure sizes increases the number of possible conformers exponentially, this makes it almost impossible to determine the polymerization enthalpy computationally. The main purpose of this study is to obtain the most stable geometries of the structures with different repeating units of polylactide by simulated annealing method instead of conformation analysis. The structures obtained from the conformation analysis (MMFF94) of oligomers with repeated units up to 1-5 and the geometric structures obtained from simulated annealing method were optimized using the B3LYP/6-31G+(d,p) method. Whether the optimum structures are minimum on the potential energy surface was confirmed by harmonic frequency analysis. The results of both methods were compared to evaluate whether similar geometries were obtained.