Isotactic polybutene-1 (PB1) has outstanding mechanical properties. However, its applications are limited compared to those of the lighter olefin polymers such as polyethylene and polypropylene. One main reason is the complication introduced by crystal structure transformations. PB1 is polymorphous, with form I (trigonal form) and form II (tetragonal form) as the most common structures. Form I is stable and form II is metastable, but despite the metastability it is always form II which is obtained when PB1 crystallizes from the melt. The transformation to form I then takes place after cooling to room temperature, accompanied by strain of crystallized samples; several days are needed for it. Because of this transformation and strain, direct melt crystallization of PB1 form I has long been a big issue. In the 1990's, Kopp et al.¹ reported a breakthrough in forming form I. They successfully crystallized the form I in the melt via epitaxy on aromatic acids or salts, and demonstrated that the form I can grow in the melt even at atmospheric pressure if appropriate substrates are provided. We presented a new solution to this problem in our recent study².  Using solution-grown form I crystals as nuclei, we demonstrated that the form I crystals can grow in the melt via self-seeding at atmospheric pressure.

In the present work, we report the preliminary study of the morphology of PB1 form I single crystals coexisting with form II spherulites and form I single crystals in thin films. We are going to discuss briefly the influence of form II spherulite growth on the growth shape of melt crystallized PB1 forn I crystals grown by self-seeding.

¹ Kopp, S.; Wittmann, J.C.; Lotz, B, Polymer 35, 916, 1994.

² Yamashita, M.; Hoshino, A.; Kato, M, J. Polym. Sci. Part B: Polym. Phys. 45, 684, 2007.

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