Promoted Stereocomplex Crystallization in Supramolecular Stereoblock Copolymers of Enantiomeric Poly(Lactic Acid)s

详细信息    查看全文

• 作者：Jianna Bao ; Ruoxing Chang ; Guorong Shan ; Yongzhong Bao ; Pengju Pan
• 刊名：Crystal Growth & Design
• 出版年：2016
• 出版时间：March 2, 2016
• 年：2016
• 卷：16
• 期：3
• 页码：1502-1511
• 全文大小：731K
• ISSN：1528-7505

文摘

Telechelic and 3-arm star-shaped poly(pan class="smallcaps">lpan>-lactic acid)s (PLLAs) and poly(pan class="smallcaps">dpan>-lactic acid)s (PDLAs) end-functionalized by 2-ureido-4[1H]-pyrimidione (UPy) self-complementary quadruple hydrogen-bonding motifs were synthesized by terminally modifying the corresponding hydroxyl-terminated polymers. The PLLA/PDLA stereoblock supramolecular polymers (sb-SMPs) with linear and branched architectures were further prepared by mixing the UPy end-functionalized telechelic, 3-arm star-shaped PLLA and PDLA through the dimerization of UPy groups, as verified by viscometry. Crystallization kinetics, polymorphic crystalline structure, and lamellae morphology of the PLLA/PDLA sb-SMPs were investigated and compared with the corresponding blends without UPy end functionalities. Compared to the PLLA/PDLA blends, the sb-SMPs exhibit higher crystallization rate and prefer to crystallizing into the high-melting-point stereocomplex (sc), rather than the low-melting-point homocrystallite in both the nonisothermal and isothermal crystallization processes. The sc crystallization ability and crystallization rate of sb-SMPs are further enhanced with increasing the concentration of terminal UPy groups or decreasing the block lengths of PLLA and PDLA. The enhanced sc crystallization ability and faster crystallization rate of sb-SMPs are ascribed to the hydrogen bonding interactions formed between the terminal UPy groups of PLLA and PDLA. Due to the preferential sc crystallization, the sb-SMPs exhibit smaller long periods than the corresponding PLLA/PDLA blends.