https://doi.org/10.1351/goldbook.14219
One of the different crystalline phases in which a given substance is able to crystallize.
Notes:
- Different polymer crystal polymorphs are characterized by different crystal lattices and different packing of stems.
- A given polymer in its different crystal polymorphs may display the same conformation and the same chain identity period, but possibly involve packing of isochiral only or of enantiomeric helices (e.g., isotactic polypropylene in its \(\ce{\upalpha\mbox{-}form}\), \(\ce{\upbeta\mbox{-}form}\), and \(\ce{\upgamma\mbox{-}form}\); syndiotactic polypropylene, forms I and II. Polymorphs are, in such cases, isoconformational, and polymorphism is determined only by different modes of packing.
- In other cases, along with the packing, the local conformations of chains are different in its different crystal polymorphs. The chain identity period and the symmetry will also differ (e.g., isotactic poly(but-1-ene), crystal forms I, II, and III; syndiotactic polypropylene, crystalline forms I, III, and IV).