The coexistence of thin and thick lamellae of form II in isotactic polybutylene-1 (PB-1) was obtained by isothermal crystallization at high temperature (100 °C) and subsequent cooling, and then the transformation from coexisted thin and thick lamellae of form II to form I was investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), in-situ wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS), to understand the dependence of lamellar thickness on the transformation from form II to form I. It is seen that the transformation of thick lamellae is always superior to that of thin lamellae. The crystal transformation time is shortened to $\sim$48 h for the samples with only thick lamellae of form II, which also weakens the retardance of form II to form I transition at late stage. By directly observing the crystalline morphology via POM, we find that crystalline form II formed at higher isothermal temperatures possesses loose and irregular spherulites, which facilitates the transition in contrast with the dense and regular spherulites formed at lower temperatures. Moreover, the large temperature difference during cooling from higher isothermal temperature to room temperature also accelerates the transformation due to increasing internal stress. Our work builds up connections among the crystalline morphology, the lamellar thickness, and the transformation behavior, which may help understand the crystalline transformation from form II to form I in PB-1.

通过在高温（100°C）下等温结晶并随后冷却，然后从共存的形式II的薄层和厚层转化，可以得到等规聚丁烯-1（PB-1）中的形式II的薄层和厚层共存。通过差示扫描量热法（DSC），偏振光学显微镜（POM），原位广角X射线衍射（WAXD）和小角X射线散射（SAXS）研究了I型从晶型II到晶型I的转变中的层状厚度。可以看出，厚的片状体的转化总是优于薄的片状体。晶体转化时间缩短至$〜$对于只有厚的晶型II的样品，需要48 h，这也会减弱晶型II在后期转变为晶型I的阻滞性。通过经由POM直接观察晶体形态，我们发现在较高等温温度下形成的晶型II具有疏松和不规则的球晶，与在较低温度下形成的致密和规则的球晶相反，其促进了转变。而且，从较高的等温温度到室温的冷却过程中的大温差也由于内部应力的增加而加速了转变。我们的工作建立了晶体形态，层状厚度和相变行为之间的联系，这可能有助于理解PB-1中从II型到I型的晶体转变。