Synthesis and Morphology Characterization of Different Architecture of Amphiphilic Block copolymers, Polystyrene-block-Poly[3-(trimethoxysilyl)propyl methacrylate] and Polystyrene-block-Poly [2-(dimethylamino)ethyl methacrylate]
Date Issued
2007
Date
2007
Author(s)
Hsu, Jung-Ching
DOI
en-US
Abstract
Amphiphilic block copolymers have been extensively studied recently. They can not only be prepared by versatile synthetic approaches but also have multiple morphologies generated from its different chemical interaction between two blocks or environment. In this study, amphiphilic block copolymer with one block of PS and another environmental-sensitive block of Poly[3-(trimethoxysilyl)propyl methacrylate] (PMSMA) or Poly [2-(dimethylamino)ethylmethacrylate] (PDMAEMA) were successfully synthesized by atom transfer radical polymerization. Besides linear architecture, heteroarm star copolymer PSn-PDMAEMAn was also synthesized and characterized. Two issues will be addressed in the thesis: (1) correlation of morphology of linear PS-b-PMSMA with PS/PMSMA selective mixed solvent; (2) correlation of morphology of linear PS-b-PDMAEMA and heteroarm PSn-PDMAEMAn star polymer in PDMAEMA selective mixed solvent and different pH and temperature.
Polystyrene-block-poly[3-(trimethoxysilyl)propyl methacrylate] was successfully prepared by the ATRP method. The spherical morphology was mostly observed in different ratio of anisole/PS-selective solvent (THF and EA) but vesicle was obtained at a very high volume ratio. On the contrary, the morphologies observed at PMSMA selective solvent of anisole/methanol system are mainly LCMs and spheres. The morphology of LCMs could be due to secondary aggregation of primary micelles or reverse micelle.
For linear PS116-b-PDMAEMA15 in pure solvent, the corona repulsion force and the core dimension determined the morphology. In THF solvent, the corona repulsion force was dominant and thus the sphere morphology was observed. With increase hydrophilic characteristic of the solvent, the corona repulsion force decreased and the vesicle morphology in 1,4-dioxane and large compound micelles in DMF were observed. For both architectures, the large compound micelles and bowl-shape micelle is mainly observed in PDMAEMA selective solvent using THF and 1,4-dioxane as the common solvents but the bowl-shape cannot be observed in DMF common solvent. It suggests that the common solvent affinity with both blocks is an important factor to form bowl-shape morphology. For linear PS116-b-PDMAEMA15, the morphologies change from lamellae (pH=3.1) to sphere (pH=7.0) and to sphere aggregates (pH=11.5) because of the pH-sensitivity of PDMAEMA segment. For star PS6-PDMAEMA6, the morphologies changes from spherical-like (pH=3.1) to large aggregate (pH=7.0), and to featureless aggregates (pH=11.5). The confined structure of PS6-PDMAEMA6 heteroarm star copolymers have both hydrophobic PS and PDMAEMA aggregated in the core caused the precipitation and featureless morphology of in pH=11.5 solution. Besides, the effect of the heating and cooling process could result in a significant morphology change for both linear and heteroarm PS6-PDMAEMA6. A preliminary study suggests that a reversible morphology change is obtained in 1,4-dioxane solvent.
Subjects
嵌段共聚物
形態學
自組裝
微胞
聚乙烯
block copolymer
morphology
self-assemble
micelle
polystyrene
Type
thesis
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