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Stereosequences of PPC: (a) (R)- and (b) (S)-isomers; (c) (R,R)-, (d) (R,S)-, (e) (S,R)-, and (f) (S,S)-diads. (R,R)- and (S,S)-diad combinations are designated as meso, and (R,S)- and (S,R)-diad ones as racemo. When the polymeric chain is composed of only meso (racemo) couplings, the stereoregularity is termed isotactic (syndiotactic).
