Cationic polymerization of penta-1,3-diene with catalytic systems based on organoaluminum compounds (AlEtCl₂, AlEt₂Cl, and AlEt₃) in combination with isopropyl chloride makes it possible to synthesize completely soluble solid polymers in a high yield with the softening point in the range from 81 to 91 °C. The signals of carbon atoms of the head isopropyl groups connected with 1,4-trans-unit of polypentadiene were identified using ¹H and ¹³C NMR spectroscopy with the T₂ filter, as well as ¹H, ¹³C HSQC and HMBC 2D NMR spectroscopy.