Variations related to the thermal behavior and morphology of isotactic polypropylenes (i-PP) with p-phenylen-bis-maleamic acid groups are studied in this work. Changes in peak temperatures and crystalline levels are discussed on the basis of not only the grafting degree of each sample but also of the experimental conditions used to obtain them. A secondary crystallization phenomenon is found to emerge from the second fusion scan, and confirmed by morphological studies. An explanation of this phenomenon is established on the basis of the grafted groups bonded in the polypropylene macromolecular backbone.