介观相分离对烯烃嵌段共聚物结晶动力学的影响

研究了介观相分离对烯烃嵌段共聚物(OBC)结晶动力学的影响.结果表明,OBC在保持介观相分离形态的情况下,结晶以三维生长的方式进行.原因可能是由于OBC的“相区溶合”造成的.OBC嵌段长度和嵌段数目存在一定的统计分布,其中某些较短的结晶性链段“溶解”于非晶区,这部分结晶性链段在结晶时起到了“传递”结晶的作用.

EFFECT OF MESOPHASE SEPARATION ON THE CRYSTALLIZATION DYNAMICS OF OLEFIN BLOCK COPOLYMERS

The present study examined the effect of mesophase separation on the crystallizaiton behavior of olefin block copolymer(OBC).Two OBCs with different ΔC8(octene content difference between the soft and hard segments) were chosen,which were shown to have different phase and crystallization morphology in the solid state.The melt morphology was further examined by rheology.The isothermal crystallization dynamics of OBCs was investigated by differential scanning calorimetry(DSC).The morphology of OBCs after isothermal crystallization was observed utilizing an atomic force microscope(AFM).The results showed that the both the two OBCs exhibited mesophase separation well above the melting temperature.Upon isothermal crystallization,the OBC with higher ΔC8 kept the mesophase separated morphology,while the OBC with lower ΔC8 displayed random distributed lamellar structure.Both the two OBCs had Avrami parameter n ≈ 3,indicating that crystallization of OBC with mesophase separation exhibited a three dimensional spread manner.This striking phenomenon was attributed to the "phase mixing" in OBCs.Some shorter crystalline hard segments can dissolve in the amorphous soft phase,which can transfer the growth of crystals into adjacent hard segment domains upon crystallization.