Structure of isotactic propylene-pentene copolymers

The structure of isotactic propylene-pentene copolymers (iPPe) was studied for the demonstration of the general principle of density-driven phase formation in polymers. All copolymerization were performed at 60°C in a 250 mL Pyrex reactor, agitated with magnetic stirrer, containing a toluene solution of the catalyst, and liquid pentene. The inclusion of hexane units in the crystals increased the density that allowed crystallization of 3-fold helical chains in the trigonal form, where the helical symmetry of the chains was maintained in the crystal lattice giving a structure similar to that of form I of isotactic polybutene (iPB). The result indicated that the crystal structure of the propene-hexene copolymers fulfilled the principle of polymer crystallography and indicated that the packing of polymer molecules is mainly driven day density.