Figure 2. Structural formulas of polystyrene showing enough repeat units along the polymer chain backbone to illustrate the differences in tacticity: (a) isotactic polystyrene (i-PS) can crystallize; (b) syndiotactic polystyrene (s-PS) can crystallize; and (c) atactic polystyrene (a-PS) cannot crystallize.

From

Experiment to Teach Multiple Melting Phenomena in Semicrystalline Polymers Using Differential Scanning Calorimetry

Kathy L. Singfield, Ashley J. Rowe

World Journal of Chemical Education. 2021, 9(3), 68-76 doi:10.12691/wjce-9-3-1