Lamellar crystal thickness transition of melt‐crystallized isotactic polybutene‐1 observed by small‐angle X‐ray scattering

The first‐order long period L 1 , the second‐order long period L 2 and lamellar crystal thickness l c of isotactic polybutene‐1 have been investigated for crystallization in the melt over a wide range (313.2 to 363.2 K) of crystallization temperatures by small‐angle X‐ray scattering experiments and density measurements. The long period L 1 shows a single linear dependence on inverse supercooling. The crystal thickness l c , however, demonstrates two linear dependences on inverse supercooling and a transition from one dependence to the other has been observed around 338.2 K, where l c becomes comparable with the radius of gyration R g of the samples.