A new aryl polyester, poly(pentamethylene terephthalate) (PPT) with five methylene groups in the repeat unit, was synthesized. Its multiple-melting behavior and crystal structure were analyzed with differential scanning calorimetry and wide-angle X-ray diffraction. In addition, the spherulitic/lamellar morphology of melt-crystallized PPT was investigated. Typical Maltese-cross spherulites (with no rings) were seen in melt-crystallized PPT at low temperatures (70-90 degreesC), but ring patterns were seen in PPT crystallized only at temperatures ranging from 100 to 115 degreesC, whereas rings disappeared with crystallization above 120 degreesC. The mechanisms of the rings in PPT were explained with several coordinated directional changes (wavy changes, twisting changes, and combinations) in the lamellae during growth. Scanning electron microscopy, in combination with atomic force microscopy, further proved that the ringed spherulites originated from the aggregation of sufficient numbers of edge-on lamellar crystals; the radial-growth edge-on/flat-on lamellae could be twisted and/or waved to form realistic band patterns. A postulated model properly described a possible origin of the ring bands through combined mechanisms of waving (zigzagging) and twisting (spiraling) of the lamellae during crystallization. Superimposed twisting and/or wavy models during crystallization were examined as examples. (C) 2004 Wiley Periodicals, Inc.