(505b) Many-Scale Molecular Modeling of Pet/Pen Blends

Poly(ethylene 2,6-naphthalate) (PEN) has naphthalene rings in its main chain in place of benzene rings of poly(ethylene terephthalate) (PET). Accordingly, PEN has higher modulus, melting, and glass transition temperature than PET. PEN has also a higher barrier property for oxygen and carbon dioxide, which makes if more suitable for food packaging. However, PEN is an expensive resin, and it may not be always feasible for large scale, industrial applications. For this reason, PET/PEN blends have attracted considerable interest in recent years. PET and PEN have been known to be immiscible with each other; however, during melt blending, they undergo a transesterification reaction, which creates PET/PEN block copolymers that act as a compatibilizer between the PET and PEN phases, improving miscibility of the blend. As the extent of the transesterification reaction increases, two phenomena take place. First, more block copolymers are formed, further improving miscibility. Second, the PET and PEN sequence lengths of the existing PET/PEN block copolymers decrease, making the copolymer more random in nature. The objective of this work is to present a detailed analysis of the phase behavior, structures, morphologies and properties of PET/PEN blends at different levels of transesterification reaction, as quantified by the polymer degree of randomness (DR), by molecular simulation. To this purpose, we resorted to a many-scale modeling approach, involving scales ranging from quantum-mechanics to finite-difference simulations.