Fig. 2. Molecular ordering of PSC films under strain.

a Illustration of GIXD measurement of a stretched PSC film. The sample stage can be rotated to define the direction of the incident X-ray beam with respect to the stretching direction (angle φ) from φ = 0 (i.e., X-ray beam is perpendicular to the strain direction) to 90° (i.e., X-ray beam is parallel to the strain direction). b rDoC of P1–P4 films as a function of strain. We note that for these incident directions, the scattering vector is not quite parallel (perpendicular) to the strain directions; however, the impact of this limitation is small as the Bragg angles are small for the lamella peak. The crystallinity value is integrated from the diffraction signal in GIXD patterns and is normalized to the initial (0% strain) state for each polymer. c The strain-dependent coherence length (i.e., mean crystal size) and d packing orientation of P1–P4 films. Edge-on and face-on fractions are defined as the integrated intensity of the (010) reflection from χ = 0–45° and χ = 45–90°, respectively. Significant changes of molecular organization are shown under strain for polymers of various molecular weights. The results shown above were averaged from at least 2 samples over 2 batches. e Schematic illustration of molecular dynamics of high and low molecular weight films under strain. The impact of molecular ordering on the resultant mechanical behavior is depicted.