The morphology and crystal growth kinetics of isotactic polybutene-1 trigonal phase in molten thin films have been studied with transmission electron microscopy, electron diffraction and optical microscopy. The growth rate of trigonal crystals was determined by in-situ optical microscopy. It is one-hundredth that of the isotactic polybutene (it-PB1) tetragonal crystals. The growth rate of trigonal crystals, as well as that of tetragonal crystals, shows the supercooling dependence derived from the nucleation theory. Trigonal crystals grown at 75 and 90.1 degrees C possessed well-facetted morphology, which suggests the existence of flat growth faces required for nucleation theory between 75 and 90.1 degrees C. This is consistent with the observed temperature dependence of trigonal crystal growth rate in accordance with the nucleation theory. (c) 2007 Elsevier B.V. All rights reserved.