The article “Detailed Atomistic Simulation of the Segmental Dynamics and Barrier Properties of Amorphous Poly(ethylene terephthalate) and Poly(ethylene isophthalate)” seeks to address “the structural, conformational, dynamic, and barrier properties of the amorphous (glassy and melt) phases of two polyisomers, PET [poly(ethylene terephthalate)] and PEI [poly(ethylene isophthalate)]”, as mentioned in its abstract (p.2978). In the introduction section, article clearly explains the importance of this study by giving a wide variety of applications of Poly(ethylene terephthalate) (PET) is used in the assembling and bundling enterprises because of its unrivaled obstruction properties in examination with other polymers, but losing its competitive edge in the market to a structurally similar polymer Poly(ethylene-2,6- naphthalene).(PEN) due to its improved quality, warm dependability, and hindrance properties, all at the expense of the higher expense related with the generation and utilization of PEN. Inorder to overcome this disadvantage associated with PEN, industries started favoring copolymers or blends based on PET especially PETI (a copolymer based on the blends of PET and PEI). The primary reason for favoring this copolymer is the improved barrier properties. Schematic representation of the PET and PEI repeat units is shown in Figure 1. The present article elucidates the molecular level mechanism responsible for the improved barrier properties of Poly(ethylene isophthalate), PEI, as compared to PET which also answer the question why PETPEI copolymers shows enhanced barrier properties in comparison with pure PET. The authors have used a fairly improved methodology to carry out this work which includes the utilization of a point by point constrain field, age of sensible atomistic designs and the detailed analysis of the static (density, conformational properties, structural properties), dynamics (phenyl ring motions) and barrier properties (oxygen diffusivity) of the two polyesters by performing appropriate statistical averaging over several uncorrelated configuration.