Control of Nanostructural Dimension by Crystallization in a Double-Crystalline Syndiotactic Poly(4-methyl-1-pentene)-block-poly(l-lactide) Block Copolymer

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• 作者：Yeo-Wan Chiang ; You-Wei Huang ; Shih-Hung Huang ; Pei-Sun Huang ; Yung-Cheng Mao ; Chih-Kuang Tsai ; Chin-Shuo Kang ; Jing-Cherng Tasi ; Chun-Jen Su ; U-Ser Jeng ; Wen-Hsien Tseng
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：August 21, 2014
• 年：2014
• 卷：118
• 期：33
• 页码：19402-19414
• 全文大小：784K
• ISSN：1932-7455

文摘

The control of nanostructural dimension by crystallization-induced chain stretching was investigated in a novel double-crystalline block copolymer, syndiotactic poly(4-methyl-1-pentene)-block-poly(l-lactide) (sPMP鈥揚LLA), featuring a lamellar phase. Because of the similar glass transition temperatures of sPMP and PLLA, their blocks could crystallize under soft confinement (i.e., a crystallization temperature higher than the glass transition temperatures of the constituent blocks) in sPMP鈥揚LLA. With the strong segregation of sPMP鈥揚LLA, the first-crystallized sPMP block was templated by microphase separation to form confined crystalline sPMP lamellae within the microphase-separated lamellar texture. Most interestingly, the first-crystallized sPMP block may also induce significant stretching of the PLLA chains from the lamellar interface, resulting in the increase of microdomain thickness of the PLLA block. With the increase of crystallization temperature, this chain stretching may become more significant, resulting in a large increase (34%) of the lamellar long period. The double-crystalline lamellar morphologies having homeotropic orientation for both sPMP and PLLA crystals can be acquired in the shear-aligned sPMP鈥揚LLA as evidenced by simultaneous 2D small-angle X-ray scattering and wide-angle X-ray diffraction, giving uniform birefringence under polarized light microscope with thermal reversibility. As a result, the switchable lamellar nanostructures having significant dimensional change can be carried out by simply controlling crystallization or melting of the crystallizable blocks.