可分解性聚酯嵌段共聚物之合成與自組裝行為之研究

Synthesis and Self-assembly of Degradable Polyester-containing Block Copolymers

曹瑋玲

指導教授 ： 何榮銘

國立清華大學/工學院/化學工程學系/碩士(2010年)

https://doi.org/10.6843/NTHU.2010.00179

摘要

The chiral effect on the self-assembly of block copolymers has been demonstrated for a block copolymer system containing chiral entities (i.e. a chiral block copolymer (BCP*)), poly(styrene)-b-poly(L-lactide) (PS-PLLA BCPs*), and it leads to the formation of new phases such as helical phase (H*). To comprehend the effect of chirality on BCP self-assembly, a series of poly(4-vinyl pyridine)-b-poly(L-lactide) (P4VP-PLLA) BCPs* were synthesized. Similar to the PS-PLLA, a helical phase can be found in the self-assembly of the P4VP-PLLA BCPs*. Also, we aim to investigate the mechanisms of chiral information transfer from molecular level to macroscopic level through self-assembly. P4VP-PDLA BCPs* were synthesized for self-assembly so as to compare the self-assembling results of P4VP-PLLA. Vibration circular dichroism (VCD) spectroscopy was used to examine the handedness of helical chain conformation. The results indicated that the P4VP-PLLA and P4VP-PDLA BCPs* possess left- and right-handed helical chain conformations, respectively. A red shift in the circular dichroism (CD) spectra of BCPs* chains in solution reflected the occurrence of aggregation so as to lead the formation of helical superstructures. It is intuitive to suggest that one-handed superstructures can be obtained from the self-assembly through chiral information transfer. Interestingly, right-handed helical superstructures were found from the self-assembly of P4VP-containing BCPs* in solution regardless of enanitomeric character. As a result, the chiral information might be missing as the BCPs* self-assemble into higher organizational levels; namely, the chiral information transfer can not be successfully achieved. To truly examine the self-assembly mechanisms and the corresponding morphological evolution, in particular, the issue with respect to handedness control, the self-assembly processes were controlled by changing the self-assembly conditions such as temperature or solvent. With the appropriate conditions for self-assembly, the formation of left-handed helical superstructures can be achieved from the self-assembly of P4VP-containing BCPs* in solution.
For nanopatterning, a series of diblock copolymers, poly(styrene)-b- poly(3-hydroxybutyrate) (PS-PHB), with PHB hexagonal cylinder (HC) nanostructures were synthesized in this study. Well-oriented, perpendicular PHB cylinders of PS-PHB thin films were efficiently achieved by spin coating using appropriate solvents regardless of the use of substrates. After hydrolysis of PHB, well-oriented HC nanochannel arrays over large area in addition to uniform surface with controlled thickness and domain size can be obtained; providing a simple and efficient path to prepare nanopatterned templates for applications. The induced orientation of PS-PHB microdomains is strongly dependent upon the evaporation rate of solvent and its solubility between constituted blocks. Consistent with our previous studies, the primary concern of controlled morphology for nanopatterning is to develop ordered microphase-separated morphology by considering the time scale for segregation, namely segregation strength during solvent evaporation. The induced orientation is attributed to the permeation discrepancy between phase-separated microdomains. The lower Tg for PHB as compared to PLLA provides a much easier way for nanopatterning due to the alleviation of the thin-layer PLLA forming on the substrate so that it is possible to acquire the well-defined nanopatterns under ambient conditions. The perpendicular morphology is initiated from the air surface, and formed in order to create an optimized condition (i.e. the fastest path) for solvent evaporation whereas parallel morphology may impede the evaporation of solvent molecules. Following the microphase separation, the perpendicular morphology can be kinetically induced by solvent evaporation.

關鍵字

掌性嵌段共聚物 ； 螺旋體超結構 ； 旋性控制 ； 擴散

並列摘要

無資料

並列關鍵字

chiral diblock copolymer ； helical superstructure ； handedness control ； diffusivity

參考文獻

1. Whitesides, G.M.; Grzybowski, B. Science 2002, 295, 2418.

5. Whitesides, G.M.; Ismagilov, R.F. Science 1999, 284, 89.

6. Bate, F. S.; Fredrickson, G. H.; Annu. Rev. Phys. Chem. 1990, 41, 525.

8. Muthukumar M.; Ober C.K.; Thomas E.L. Science 1997, 277, 1225.

9. Lodge, T.P. Macromol Chem Phys 2003, 204, 265.