Synthesis and Characterization of Brush Linear and Cyclic Polymers Bearing Functional Groups at the Bristle Ends
- Synthesis and Characterization of Brush Linear and Cyclic Polymers Bearing Functional Groups at the Bristle Ends
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- Polymer materials have received immense attention in biocompatible materials, biosensing devices, memory devices and electrochemicals because of their low-cost fabrication, high flexibility, high mechanical strength, and good scalability. In addition, polymer materials can be tailored by changing their chemical structure and their topological structure. That is, their function can be improved by incorporating specific molecules into the polymer backbone or side chain. Especially, cyclic polymers exhibit unique topological effects on physical properties such as chain dimensions, viscoelastic properties, chain dynamics and their self-assembly behaviors. There has been considerable research into cyclic polymers in recent years.
In Chapter II, DNA-mimicking new brush polymer bearing nucleobase moieties were synthesized: Poly(4-hydroxybutyl acrylate)s and Poly(9-hydroxynonyl acrylate)s – A (adenine), G (guanine), T (thymine), U (uracil), and C (cytosine). We report the first digital nonvolatile memory devices fabricated with DNA-mimicking brush polymers. DNA-mimicking brush polymer devices revealed p-type unipolar write-once-read-many-times memory behaviors with low switching-on voltage and high ON/OFF current ratio. Such permanent memory characteristics were confirmed to originate from the charge trapping and hopping nature of nucleobase moieties. Overall, this study demonstrated that DNA-mimicking polymers are good candidate materials for the production of p-type permanent memory devices with high performance, high stability and low power consumption.
In Chapter III, cyclic copolymer was synthesized and characterization: Cyclic Poly (allyl glycidyl ether-b-ethoxyethyl glycidyl ether) (Cyclic-PAGE-b-PEEGE). We synthesized linear diblock copolyethers from AGE and EEGE by anionic ring opening polymerization with α-azido group which is versatile and selectively functionalizable polyether and free from side reactions. The obtained N3-PAGE-b-PEEGE-OH was reacted with a propargyl bromide using NaH in THF to give α, ω-telechelic polyether linear precursor N3-PAGE-b-PEEGE-C≡CH. In order to optimize the reaction condition of ring-closure reaction using CuAAC, we tested various conditions. Through the following results, we optimized solvent (DMF), temperature (120 oC), injection rate (0.5 mL/h), and polymer solution concentration (0.2 μmol/mL) to optimize CuAAC ring-closure reaction conditions. To know reaction mixture were analyzed before and after recycling by 1H NMR measurements and analytical size exclusion chromatography (SEC). Also through a qualitative and quantitative analysis of practical cyclization reaction efficiency, we can get a pure product efficiently by changing the concentration.
In Chapter IV, new amphiphilic brush cyclic diblock copolymers bearing pH labile linker (hydrazine bond), anticancer drug (paclitaxel), dye (IR-820) and specific ligand (galactosamine) were synthesized: Cyclic Poly (glycidyl benzyl-2-(propylthio)acetate -b-glycidyltetraoxatridecane)s (Cyclic-PGHPTAH-b-PGTTD), (Cyclic-PGHPTAH-b-PGTTD with PTX&IR-820&GalN), (Cyclic-PGHPTAH-b-PGTTD with PTX), (Cyclic-PGHPTAH-b-PGTTD with PTX&IR-820), (Cyclic-PGHPTAH-b-PGTTD with IR-820), and (Cyclic-PGHPTAH-b-PGTTD with GalN). These cyclic diblock copolymers were synthesized free from side reactions with narrow and controlled molecular weight distribution by sequential living polymerization, CuAAC click reaction and subsequent selective post-functionalizations. Moreover, the synthesized cyclic brush polymers bearing pH labile linker (hydrazine bond), anticancer drug (paclitaxel), dye (IR-820) and specific ligand (galactosamine) formed stable polymeric micelles in aqueous and organic solvents. Using these results, creating desired micelle structures will be easier, and this can be applied to promising studies that use micelles as drug carriers.
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