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가역적 졸-젤 전이 능력을 가진 3차원 분자 및 섬유소 네트워크에 대한 연구

Title
가역적 졸-젤 전이 능력을 가진 3차원 분자 및 섬유소 네트워크에 대한 연구
Other Titles
Molecular and Fibrillary 3D Complex Networks with Tunable Sol-Gel Transitions
Author
이예람
Advisor(s)
김진웅
Issue Date
2017-02
Publisher
한양대학교
Degree
Master
Abstract
Temperature-responsive hydrogels were fabricated by the photo-polymerization of bis-acryloyl poloxamer tri-block copolymers, and their temperature-responsive behavior and physiological effect on skin were investigated. For this, poloxamer macromers were prepared by end-capping both terminal hydroxyl groups of poloxamer tri-block copolymers with acrylates. They were then photo-polymerized to generate polymeric hydrogels with structural integrity that allowed excellent stability against dilution in an aqueous environment. The resulting hydrogels exhibited dramatic reversible swelling behavior upon changes in temperature. A demonstration experiment, in which the hydrogels were applied topically to the skin, showed that they shrank rapidly as a result of the increase in temperature, owing to the contact with the skin surface, highlighting their effectiveness for instantaneously moisturizing the skin.|Cellulose fibrils can pact to form a crystalline structure with an extended chain conformation. Thanks to this unique molecular structure, they display excellent structural stability as well as unique rheological fluidity. Herein, we report an approach to fabricate hydrophobically associative cellulose nanofibers (ACNFs) by using combined surface-mediated living radical polymerization and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation. More specifically, cellulose nanocrystals were grafted with poly (stearyl methacrylate-co-2-methacryloxyethyl phosphorylcholine) brushes. Then, TEMPO-mediated oxidation was conducted to produce nanoscale ACNFs. The ACNFs displayed the hydrophobic attraction-driven interfibrillary association, thus leading to production of a nanofibrillary gel fluid. We observed that the viscosity of the ACNF fluid showed reversible thinning and thickening in responsive to applied shear stress as well as thermal shock. Thanks to the generation of a mechanically robust nanofibrillary gel network, the ACNF solution displayed excellent structural resistance to salinity and pH changes. The results obtained in this study highlight that the interfibrillary hydrophobic association of ACNFs indeed important and play a role in regulation of stimuli-responsive sol-gel transitions.
Cellulose fibrils can pact to form a crystalline structure with an extended chain conformation. Thanks to this unique molecular structure, they display excellent structural stability as well as unique rheological fluidity. Herein, we report an approach to fabricate hydrophobically associative cellulose nanofibers (ACNFs) by using combined surface-mediated living radical polymerization and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation. More specifically, cellulose nanocrystals were grafted with poly (stearyl methacrylate-co-2-methacryloxyethyl phosphorylcholine) brushes. Then, TEMPO-mediated oxidation was conducted to produce nanoscale ACNFs. The ACNFs displayed the hydrophobic attraction-driven interfibrillary association, thus leading to production of a nanofibrillary gel fluid. We observed that the viscosity of the ACNF fluid showed reversible thinning and thickening in responsive to applied shear stress as well as thermal shock. Thanks to the generation of a mechanically robust nanofibrillary gel network, the ACNF solution displayed excellent structural resistance to salinity and pH changes. The results obtained in this study highlight that the interfibrillary hydrophobic association of ACNFs indeed important and play a role in regulation of stimuli-responsive sol-gel transitions.
URI
http://dcollection.hanyang.ac.kr/jsp/common/DcLoOrgPer.jsp?sItemId=000000100722https://repository.hanyang.ac.kr/handle/20.500.11754/124901
Appears in Collections:
GRADUATE SCHOOL[S](대학원) > BIONANOTECHNOLOGY(바이오나노학과) > Theses (Master)
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