Development of tethered micelle hydrogel networks through sphere-forming AB/ABA block copolymer melts
| dc.contributor.author | Guo, Chen, author | |
| dc.contributor.author | Bailey, Travis S., advisor | |
| dc.contributor.author | Kipper, Matt J., committee member | |
| dc.contributor.author | Chen, Eugene, committee member | |
| dc.contributor.author | Wickramasinghe, S. Ranil, committee member | |
| dc.date.accessioned | 2007-01-03T06:08:46Z | |
| dc.date.available | 2016-01-31T05:57:00Z | |
| dc.date.issued | 2013 | |
| dc.description.abstract | The overriding theme of the work contained in this thesis is concerned with the preparation of tethered micelle hydrogel networks through the melt-state self-assembly of sphere-forming AB diblock and ABA triblock copolymer blends. The first chapter of this dissertation introduces the various projects pursued and provides background information for the reader. The second chapter of this thesis contains the initial demonstration of this novel strategy using polystyrene-poly(ethylene oxide) (PS-PEO, SO) diblock and PS-PEO-PS (SOS) triblock copolymers. Included in this chapter is a discussion of the synthetic polymerization techniques used to produce the SO and SOS block copolymers, the basic melt-state fabrication and characterization strategies used to pre-structure the tethered micelle networks, and the impact of changing both the SOS concentration and temperature on the resultant properties of the hydrogels produced. In these initial studies, the SOS triblock copolymer was constructed to be exactly double the SO diblock copolymer molecular weight, such that the preferred lattice dimensions during self-assembly were "matched". These "matched" hydrogels produced equilibrium swelling ratios (3.8-36.9 g water/g polymer) and dynamic elastic moduli (G' = 1.7-160 kPa) tunable across an impressive range of values using only temperature (10-50 °C) and SOS concentration (3.3-72.0 mol%). The third chapter of this thesis describes our efforts to influence the swelling and mechanical properties exhibited by simply modifying the PEO midblock molecular weight in the SOS tethering molecules. In doing so, we were able to show that the degree of coronal layer overlap between adjacent micelles was the primary contributing factor determining the dynamic mechanical response of the hydrogel. That is, the changes in mechanical properties produced due to altering tether concentration, tether length, or temperature, could all be understood in terms of their impact on the degree of coronal layer overlap in the system. In addition to these findings, we also discovered an interesting relationship between swelling and tether length. Increases in tether length by a factor of 1.6 compared to that of the matched system, resulted in higher swelling ratios and smaller elastic moduli (due to reduced coronal layer overlap). However, increases in tether length by a factor of 2.3 produced swelling behavior and mechanical properties nearly identical to that of the matched system. We concluded that the increase in tether length by a factor of 2.3 was sufficient to allow bridging into the second shell of the nearest neighbor micelles, negating the swelling advantage anticipated for the system. The fourth chapter of this thesis concerns our efforts to demonstrate the modification potential of the swollen hydrogel systems of Chapters 2 and 3. In this study, the terminal hydroxyl functionality present in the aforementioned SO diblock copolymers was substituted with either an azide or alkyne functionality. Cu(I) catalyzed coupling of the azide/alkyne functional diblock copolymer was then performed in the swollen state, producing a secondary network of tethers in the system. Installation of the secondary network produced dramatic improvements in the hydrogel tensile modulus, strain at break, stress at break, and toughness, while permitting swelling ratios, small strain rheological properties, and response in unconfined compression to remain largely unchanged. The fifth and final chapter of this thesis concerns a discussion of preliminary data supporting several promising directions for future work involving the further development of these tethered micelle networks. | |
| dc.format.medium | born digital | |
| dc.format.medium | doctoral dissertations | |
| dc.identifier | Guo_colostate_0053A_12115.pdf | |
| dc.identifier | ETDF2013500299CABE | |
| dc.identifier.uri | http://hdl.handle.net/10217/80943 | |
| dc.language | English | |
| dc.language.iso | eng | |
| dc.publisher | Colorado State University. Libraries | |
| dc.relation.ispartof | 2000-2019 | |
| dc.rights | Copyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright. | |
| dc.subject | hydrogels | |
| dc.subject | self-assembly | |
| dc.subject | nanostructures | |
| dc.subject | block copolymer | |
| dc.title | Development of tethered micelle hydrogel networks through sphere-forming AB/ABA block copolymer melts | |
| dc.type | Text | |
| dcterms.embargo.expires | 2016-01-31 | |
| dcterms.embargo.terms | 2016-01-31 | |
| dcterms.rights.dpla | This Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). | |
| thesis.degree.discipline | Chemical and Biological Engineering | |
| thesis.degree.grantor | Colorado State University | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Doctor of Philosophy (Ph.D.) |
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