Initial Lamellar Thickness Dependency of Melt Memory Effect in Isotactic Polybutene-1 above Equilibrium Melting Point

P. Liu1,2 and Y. Men1,2

1 State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Street 5625, 130022 Changchun, P.R. China
2 University of Science and Technology of China, Hefei 230026, P.R.China

Using the method of differential scanning calorimetry (DSC), it was found that isotactic polybutene-1 (iPB-1) with a specific weight average molecular weight (Mw ~ 188 kg/mol) showed an unique melt memory effect, which was dependent on the initial lamellar thickness. Even though iPB-1 was molten at the temperature (Tms) higher than the equilibrium melting point of iPB-1 (133 oC), the memory effect was still observed, which affected the subsequent crystallization behavior. Briefly speaking, the total crystallization rate increased greatly with the decrease of Tms. Moreover, the thinner the initial lamellae of the iPB-1 sample, the faster it can crystallize. The results reveal that the increase of crystallization rate is directly related to the increased density of iPB-1 nuclei originated from some “specific structures” remaining in the melt. These specific structures, considered as high temperature clusters, are rather stable since aging two hours at Tms is not able to evidently reduce nucleation density. Only if Tms is higher than 170 oC, much higher than 133 oC, the crystallization rate of iPB-1 reaches a constant value.

Acknowledgement: This work is supported by NSFC (51525305, 21134006).