- 學位論文
掌性高分子與嵌段共聚物之自組裝行為:從分子到界面之掌性傳遞與記憶效應
Transfer of Chirality from Molecule to Interface in Self-assembled Chiral Polymers and Behavior of Chirality Memory
摘要
Abstract Among self-assembled architectures, helical morphology is probably the most fascinating texture in nature. By introducing the chirality into synthetic molecules, helical textures in different length scales can be obtained by self-assembling through interplay of secondary interactions (i.e., non-covalent bonding forces). In this study, a series of chiral polylactides with an achiral chromophore moiety (i.e., pyrene) as a chain end (pyrene-labeled poly(L-lactide) (PLLA) and pyrene-labeled poly(D-lactide) (PDLA)) and polylactide-containing block copolymers (BCPs) with an achiral chromophore moiety (i.e., perylene) as a chemical junction (polystyrene-perylene-poly(L-lactide) (PS-perylene-PLLA), polystyrene- perylene-poly(D-lactide) (PS-perylene-PDLA) and polystyrene- perylene-poly(D,L-lactide) (PS-perylene-PLA)) are synthesized for self-assembly to examine the mechanisms of chirality transfer from molecular level to macroscopic texture. Banded spherulites resulting from left-handed and right-handed crystalline lamellar twisings are formed by crystallization of chiral polymers, pyrene-labeled PLLA and the pyrene-labeled PDLA, respectively. By contrast, helical phases with left- and right-handedness are formed by self-assembling of chiral BCPs (BCPs*), PS-perylene-PLLA and PS-perylene-PDLA, respectively. Through twisting and shifting at crystalline folding surface of chiral polymers and microphase-separated interface of block copolymers, significant induced circular dichroism (ICD) signals of the achiral chromophore as the chain end of polymer and the junction of constituted blocks can be driven by chiral polymer self-assembly while crystallization occurs and by BCP* self-assembly in solution while the concentration of the BCPs* in toluene solution is higher than the critical micelle concentration, respectively. Also, the induced optical activity of the achiral chromophore in the self-assembled chiral polymers and BCPs* can be well defined by the helicity of chiral entity via chirality transfer. Consequently, it is possible to create hierarchical helical superstructures such as helcial banded spherulitic textures and helical phases by using achiral chromophore at the chain end of chiral polymer and as the junction of chiral BCPs. Owing to the ICD of the achiral chromophore driven by self-assembly, novel materials with specific chiroptic properties can be fabricated. Systematic studies on the mechanisms of chirality transfer from molecular to phase chirality in the crystallization of the chiral polylactides and the self-assembly of the polylactide-containing BCPs* are carried out. The chirality of molecule in the chiral polymers is identified from electron circular dichroism (ECD) spectra while the handedness of the helical conformation in the chiral polymer is determined from split-type Cotton effect in vibrational circular dichroism (VCD) spectra. The sense of the lamellar twisting in the crystalline spherulite is determined using PLM for the comparison with the ICD signals of the achiral chromophore at which the signature of split-type Cotton effect of the achiral chromophore (as a molecular probe) in ECD spectrum can be used for the handedness determination of the lamellar twisting. On the basis of the VCD results of the chiral polylactides and the ECD results of the chromophore labeled at the chain ends of the polymers, a homochiral evolution from the chiral polymer chain (conformation chirality) to the lamellar twisting in the banded spherulite (hierachical chirality) is suggested. Micro-phase separation of the BCP* is exploited to form a helical (H*) phase, and the handedness of helical nanostructure in the BCP* is directly visualized from transmission electron microscopy tomography. In comparison with the spectroscopic experiments of the chiral polylactides, similar ECD and VCD results can be found in self-assembled polylactide-containing BCPs*. As a result, a homochiral evolution from the BCP* chain to the helical phase is suggested. Moreover, as examined by CD and fluorescence experiments, significant induced CD signals and bathochromic shift in fluorescence emission of achiral perylene moiety as a chemical junction of the BCPs* can be found once the concentration of the BCPs* in toluene solution is higher than critical micelle concentration, suggesting a twisting and shifting mechanism initiating from microphase-separated interface of the BCPs* leading to the formation of H* phase from self-assembly. Because of the unstable character of ester group, chiral polylactides in the BCPs* can be hydrolytically degraded. As evidenced by chiroptical measurements, the induced preferential helicity of the achiral chromophore in the polylactide-containing BCPs* via BCP* co-assembly can be maintained (i.e., memorized) after hydrolysis of the chiral polylactide in self-assembled BCP* thin film. By taking advantage of the achiral chromophore with preferential handedness at the microphase-separated interface (that is chirality memory effect), the hydrolyzed PS nanopores with the achiral chromophore as molecular probe is appealing for the applications in chiroptics. Most importantly, the demonstrated chirality memory effect suggests the feasibility to provide a helical contour of the chemical junctions decorated on the wall of the nanopores, giving the possibility to create functionalized nanoporous materials with defined surface properties for novel applications. Moreover, as photo-induced pyrene association is a diffusion-controlled process, the optical recording effect of pyrene-labeled chiral polylactides can be well defined through the manipulation of polymer chain mobility which is dependent on the configurational and conformation regularity. Also, because the chiral polylactides are intrinsically crystallizable polymers, the Tg and Tm of the PLCPs can be exploited as energy barriers for the induction of the association of pyrene moieties in PLCPs and the recording capabilities of the PLCPs will be dependent upon the corresponding thermal properties.
並列摘要
Abstract Among self-assembled architectures, helical morphology is probably the most fascinating texture in nature. By introducing the chirality into synthetic molecules, helical textures in different length scales can be obtained by self-assembling through interplay of secondary interactions (i.e., non-covalent bonding forces). In this study, a series of chiral polylactides with an achiral chromophore moiety (i.e., pyrene) as a chain end (pyrene-labeled poly(L-lactide) (PLLA) and pyrene-labeled poly(D-lactide) (PDLA)) and polylactide-containing block copolymers (BCPs) with an achiral chromophore moiety (i.e., perylene) as a chemical junction (polystyrene-perylene-poly(L-lactide) (PS-perylene-PLLA), polystyrene- perylene-poly(D-lactide) (PS-perylene-PDLA) and polystyrene- perylene-poly(D,L-lactide) (PS-perylene-PLA)) are synthesized for self-assembly to examine the mechanisms of chirality transfer from molecular level to macroscopic texture. Banded spherulites resulting from left-handed and right-handed crystalline lamellar twisings are formed by crystallization of chiral polymers, pyrene-labeled PLLA and the pyrene-labeled PDLA, respectively. By contrast, helical phases with left- and right-handedness are formed by self-assembling of chiral BCPs (BCPs*), PS-perylene-PLLA and PS-perylene-PDLA, respectively. Through twisting and shifting at crystalline folding surface of chiral polymers and microphase-separated interface of block copolymers, significant induced circular dichroism (ICD) signals of the achiral chromophore as the chain end of polymer and the junction of constituted blocks can be driven by chiral polymer self-assembly while crystallization occurs and by BCP* self-assembly in solution while the concentration of the BCPs* in toluene solution is higher than the critical micelle concentration, respectively. Also, the induced optical activity of the achiral chromophore in the self-assembled chiral polymers and BCPs* can be well defined by the helicity of chiral entity via chirality transfer. Consequently, it is possible to create hierarchical helical superstructures such as helcial banded spherulitic textures and helical phases by using achiral chromophore at the chain end of chiral polymer and as the junction of chiral BCPs. Owing to the ICD of the achiral chromophore driven by self-assembly, novel materials with specific chiroptic properties can be fabricated. Systematic studies on the mechanisms of chirality transfer from molecular to phase chirality in the crystallization of the chiral polylactides and the self-assembly of the polylactide-containing BCPs* are carried out. The chirality of molecule in the chiral polymers is identified from electron circular dichroism (ECD) spectra while the handedness of the helical conformation in the chiral polymer is determined from split-type Cotton effect in vibrational circular dichroism (VCD) spectra. The sense of the lamellar twisting in the crystalline spherulite is determined using PLM for the comparison with the ICD signals of the achiral chromophore at which the signature of split-type Cotton effect of the achiral chromophore (as a molecular probe) in ECD spectrum can be used for the handedness determination of the lamellar twisting. On the basis of the VCD results of the chiral polylactides and the ECD results of the chromophore labeled at the chain ends of the polymers, a homochiral evolution from the chiral polymer chain (conformation chirality) to the lamellar twisting in the banded spherulite (hierachical chirality) is suggested. Micro-phase separation of the BCP* is exploited to form a helical (H*) phase, and the handedness of helical nanostructure in the BCP* is directly visualized from transmission electron microscopy tomography. In comparison with the spectroscopic experiments of the chiral polylactides, similar ECD and VCD results can be found in self-assembled polylactide-containing BCPs*. As a result, a homochiral evolution from the BCP* chain to the helical phase is suggested. Moreover, as examined by CD and fluorescence experiments, significant induced CD signals and bathochromic shift in fluorescence emission of achiral perylene moiety as a chemical junction of the BCPs* can be found once the concentration of the BCPs* in toluene solution is higher than critical micelle concentration, suggesting a twisting and shifting mechanism initiating from microphase-separated interface of the BCPs* leading to the formation of H* phase from self-assembly. Because of the unstable character of ester group, chiral polylactides in the BCPs* can be hydrolytically degraded. As evidenced by chiroptical measurements, the induced preferential helicity of the achiral chromophore in the polylactide-containing BCPs* via BCP* co-assembly can be maintained (i.e., memorized) after hydrolysis of the chiral polylactide in self-assembled BCP* thin film. By taking advantage of the achiral chromophore with preferential handedness at the microphase-separated interface (that is chirality memory effect), the hydrolyzed PS nanopores with the achiral chromophore as molecular probe is appealing for the applications in chiroptics. Most importantly, the demonstrated chirality memory effect suggests the feasibility to provide a helical contour of the chemical junctions decorated on the wall of the nanopores, giving the possibility to create functionalized nanoporous materials with defined surface properties for novel applications. Moreover, as photo-induced pyrene association is a diffusion-controlled process, the optical recording effect of pyrene-labeled chiral polylactides can be well defined through the manipulation of polymer chain mobility which is dependent on the configurational and conformation regularity. Also, because the chiral polylactides are intrinsically crystallizable polymers, the Tg and Tm of the PLCPs can be exploited as energy barriers for the induction of the association of pyrene moieties in PLCPs and the recording capabilities of the PLCPs will be dependent upon the corresponding thermal properties.
參考文獻
延伸閱讀
- Yang, K. C. (2020). 探討分子內與分子間之掌性效應對於掌性嵌段共聚物自組裝行為的影響 [doctoral dissertation, National Tsing Hua University]. Airiti Library. https://www.airitilibrary.com/Article/Detail?DocID=U0016-0209202114071700
- 陳孟輝（2005）。利用尾端官能基化之導電高分子合成硬桿-柔曲雙團鏈共聚高分子及其性質研究〔碩士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2005.00679
- 詹益響（2010）。掌性盤狀化合物及盤狀雙聚物之合成及超分子堆疊探討〔碩士論文，淡江大學〕。華藝線上圖書館。https://doi.org/10.6846/TKU.2010.00447
- Liu, T. W. (2020). 應用於非揮發記憶體內運算之高阻態單元偏好神經網路權重量化演算法 [master's thesis, National Tsing Hua University]. Airiti Library. https://www.airitilibrary.com/Article/Detail?DocID=U0016-0209202114064117
- Leung, Q. Y. (2010). Synthesis, characterization and photovoltaic applications of fused heterocyclic molecules with intramolecular charge transfer properties [doctoral dissertation, The University of Hong Kong]. Airiti Library. https://www.airitilibrary.com/Article/Detail?DocID=U0029-1812201200018949