三嵌段共聚物PI-PS-PLLA之相行為研究

Phases Behaviors of Polyisoprene-b-Polystyrene- b-Poly(L-lactide) Triblock Terpolymers

謝奕民(Yi-Min Hsieh)

指導教授 ： 何榮銘

國立清華大學/工學院/化學工程學系/碩士(2013年)

https://doi.org/10.6843/NTHU.2013.00360

摘要

Owing to the multiple interaction parameters resulting from the presence of a distinct third block, the phase behaviors of ABC triblock terpolymers are obviously much richer than that of AB diblock and ABA triblock copolymers. The diversity of self-assembled morphologies from ABC triblock terpolymers is appealing for practical applications, in particular by tuning the chemical and physical properties of three constituent blocks. In this study, we aim to systematically examine the phase behaviors of a dual degradable triblock terpolymer, polyisoprene -b-polystyrene-b-poly(L-lactide) (PI-PS-PLLA), at which the PI block can be ozonized and the PLLA can be hydrolyzed. Moreover, the chirality effect on the self-assembly of the PI-PS-PLLA due to the presence of the chiral PLLA is examined. The final goal is to search for network morphologies so as to use them for the fabrication of nanoporous polymers through degradation of the PI and/or the PLLA.
For practical applications, network morphologies with PS or PLLA as a matrix will be acquired since the samples with PI-rich fraction is easy to be deformed due to its low Tg. A variety of nanostructured phases such as core-shell body centered cubic and core-shell double gyroid morphologies in the PI-PS-PLLA can be obtained with fPIv~0.3. With fPSv~0.35 and high amount of PLLA fraction, three-domain lamellar morphology can be found, indicating that the chirality effect of PLLA-rich samples on the self-assembly of the PI-PS-PLLA is trivial. As a result, the exploration of network phases is focused on the composition range with fPLLAv~0.35 and high amount of PS; an alternating gyroid can be found. Most interestingly, a novel network phase is discovered in a specific PI-PS-PLLA, ISL-38b (fIv=0.28; fSv=0.43; fLv=0.29), at which different projections including “knitting pattern” with sinusoidal waves and tetragonal dots combined with stacking lamellae can be observed. Nevertheless, the projections are much different from simulated images of any typical network phases acquired by Matlab and Meshlab.
To truly examine the network morphologies, direct visualization of the network texture is carried out by using electron tomography. As observed in the 3D TEM results, dark contrast PI due to the staining of OsO4 appears as “wave-tube stacking” in the bright matrix. To visualize the texture of PLLA microdomains, hydrolysis is carried out. The SEM micrographs of the hydrolyzed samples demonstrate that the PLLA microdomain should be a network texture. By taking advantage of templated sol-gel process, the PLLA microdomains can be successfully replaced by SiO2, further evidencing the suggested network texture of PLLA. The corresponding SAXS results with the reflections at the relative q values of √2: √3: √4: √6: √8: √10, reflecting that the space group of this new network phase is a Pn-- type, similar to that of double diamond (Pn m), on the basis of systematic absence principle for the reflections. A hypothetic nanostructured phase is thus proposed.

關鍵字

聚乙烯 ； 聚異戊二烯 ； 聚乳酸 ； 相行為 ； 網狀結構 ； 三嵌段共聚物

並列摘要

Owing to the multiple interaction parameters resulting from the presence of a distinct third block, the phase behaviors of ABC triblock terpolymers are obviously much richer than that of AB diblock and ABA triblock copolymers. The diversity of self-assembled morphologies from ABC triblock terpolymers is appealing for practical applications, in particular by tuning the chemical and physical properties of three constituent blocks. In this study, we aim to systematically examine the phase behaviors of a dual degradable triblock terpolymer, polyisoprene -b-polystyrene-b-poly(L-lactide) (PI-PS-PLLA), at which the PI block can be ozonized and the PLLA can be hydrolyzed. Moreover, the chirality effect on the self-assembly of the PI-PS-PLLA due to the presence of the chiral PLLA is examined. The final goal is to search for network morphologies so as to use them for the fabrication of nanoporous polymers through degradation of the PI and/or the PLLA.
For practical applications, network morphologies with PS or PLLA as a matrix will be acquired since the samples with PI-rich fraction is easy to be deformed due to its low Tg. A variety of nanostructured phases such as core-shell body centered cubic and core-shell double gyroid morphologies in the PI-PS-PLLA can be obtained with fPIv~0.3. With fPSv~0.35 and high amount of PLLA fraction, three-domain lamellar morphology can be found, indicating that the chirality effect of PLLA-rich samples on the self-assembly of the PI-PS-PLLA is trivial. As a result, the exploration of network phases is focused on the composition range with fPLLAv~0.35 and high amount of PS; an alternating gyroid can be found. Most interestingly, a novel network phase is discovered in a specific PI-PS-PLLA, ISL-38b (fIv=0.28; fSv=0.43; fLv=0.29), at which different projections including “knitting pattern” with sinusoidal waves and tetragonal dots combined with stacking lamellae can be observed. Nevertheless, the projections are much different from simulated images of any typical network phases acquired by Matlab and Meshlab.
To truly examine the network morphologies, direct visualization of the network texture is carried out by using electron tomography. As observed in the 3D TEM results, dark contrast PI due to the staining of OsO4 appears as “wave-tube stacking” in the bright matrix. To visualize the texture of PLLA microdomains, hydrolysis is carried out. The SEM micrographs of the hydrolyzed samples demonstrate that the PLLA microdomain should be a network texture. By taking advantage of templated sol-gel process, the PLLA microdomains can be successfully replaced by SiO2, further evidencing the suggested network texture of PLLA. The corresponding SAXS results with the reflections at the relative q values of √2: √3: √4: √6: √8: √10, reflecting that the space group of this new network phase is a Pn-- type, similar to that of double diamond (Pn m), on the basis of systematic absence principle for the reflections. A hypothetic nanostructured phase is thus proposed.

並列關鍵字

PI-PS-PLLA ； phase behaviors ； network morphology ； triblock terpolymer

參考文獻

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