Fig. 3
From: Unraveling substituent effects on the glass transition temperatures of biorenewable polyesters
Ramachandran-type analysis. a Model compounds for the tricyclic (2a–2c) and phthalic (2d–2f) anhydride-based polyesters considered in this work. The bonds used to specify the θ and φ dihedral angles are delineated in red and blue, respectively, with the corresponding perspectives defined above. b Graphical legend illustrating the relative orientations of the two carbonyl groups corresponding to a given set of θ and φ dihedral angles. Red and blue arrows are used to depict the orientation of the left and right carbonyl groups, respectively. For example, conformation A (with dihedral angles given by θ = 90° and φ = 90°) corresponds to a structure with the left carbonyl group orientated upward and the right carbonyl group orientated downward. c Ramachandran-type plots depicting the full 2D PES corresponding to dihedral rotations about θ and φ for each of the polyester model compounds (2a–2f). Select stationary points on each PES include a representative minimum (gold star) and its most accessible neighboring transition states (circled numbers), the structures and energetics of which will be showcased in Fig. 5. The gold star corresponds to the location of the global minimum for all cases except 2e, where the global minimum (with an energetic separation of ~0.36 kcal/mol) is indicated with a gold circle (Supplementary Discussion and Supplementary Table 6)
