Lamella-to-lamella transition and effect of coil-stretching on crystallization in a rod-coil diblock copolymer containing poly (epsilon-caprolactone)

作者：Liu Xuan Bo; Zhao Yong Feng; Chen Er Qiang^*; Ye Chun; Shen Zhi Hao; Fan Xing He; Cheng Stephen Z D; Zhou Qi Feng

来源：Macromolecules, 2008, 41(14): 5223-5229.

DOI：10.1021/ma800517k

We have studied the phase properties of a diblcok copolymer poly(epsilon-caprolactone)-block-poly(2,5bis[4-methoxyphenyl]oxycarbonyl)styrene) (PCL-b-PMPCS) with a PMPCS volume fraction of similar to 59%. The mesogen-jacketed liquid crystalline (LC) PMPCS block was amorphous in the as-east films; and would transform into a columnar (Phi) LC phase upon the first hearing and thereafter serve as rod in the copolymer studied. On the basis of simultaneous measurement of small- and wide-angle X-ray scattering (SAXS and WAXS), we identified that the original microphase-separated lamellar morphology observed in the as-cast films with amorphous PMPCS block could evolve into a new lamellar morphology with a significantly increased long period. This lamella-to-lamella transition was triggered by the amorphous-to-LC transition and was irreversible. WAXS results revealed that the chain axes of the PCL block in crystal and the rod-like PMPCS block in Phi phase were all parallel to the microphase-separated lamellar normal. Since the melting temperature of PCL crystal was well below the glass transition temperature of PMPCS block, crystallization of the PCL block was taken place in one-dimensional confined environment. Compared with those confined by the amorphous PMPCS blocks, the PCL blocks were more stretched in the confinement constructed by the Phi phase of PMPCS blocks, and thus were crystallized faster with increased fold length. This work demonstrated a lamellar phase morphology evolution based on LC phase formation of the rod block, and also indicated an effect of the degree of coil stretching on polymer crystallization.

• 出版日期2008-7-22
• 单位北京大学