1 Overview

Consideration of the structure of macromolecules starts with a look at the details of chain level chemical details which can impact the conformations adopted by the polymer. In the case of saturated carbon backbones, while maintaining the desired C_i-1 -C_i -C_i+1 bond angle of 112^∘, the placement of the final carbon in the triad above can occur at any point along the circumference of a circle, defining a torsion angle φ. We can readily recognize the energetic differences as a function this angle, U(φ) such that there are 3 minima - a deep minimum corresponding the the trans state, for which φ = 0 and energetically equivalent gauche_- and gauche₊ states at φ = ±120 degrees, as shown in Fig 1.