The main purpose of this work is to present the effect of long-chain branching and specific α-nucleation on the optical properties, crystallization and supermolecular structure of polypropylene (PP). Commercially available α-nucleating/ clarifying agent 1,3;2,4-bis(3,4-dimethylbenzylidene)sorbitol (Millad 3988) was mixed into linear PP and long-chain branched PP (LCB-PP) in the concentration of 0.2 wt%. For the study of polymorphic composition, crystallinity, and crystallization process under isothermal conditions in the temperature range of 130–150 °C, differential scanning calorimetry and wide-angle X-ray scattering were used. Although the used nucleating/clarifying agent appears to have a slight effect on the optical properties of long-chain branched polypropylene, it does not appear to affect the crystallization kinetics significantly. LCB-PP exhibited self-nucleation, favored over nucleation by a specific nucleating agent.Tomas Bata University in Zlin, TBU, (CZ.02.2.69/0.0/0.0/19_073/0016941)project OP VVV Junior Grants TBU in Zlin [CZ.02.2.69/0.0/0.0/19_073/0016941
