Native Cellulose Nanofibril-based Functional Materials
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School of Science |
Doctoral thesis (article-based)
| Defence date: 2016-11-18
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Authors
Date
2016
Major/Subject
Mcode
Degree programme
Language
en
Pages
64 + app. 32
Series
Aalto University publication series DOCTORAL DISSERTATIONS, 222/2016
Abstract
Cellulose is the most abundant polymeric source on earth, and it has been used for centuries in different applications ranging from paper making to technological materials. Recently, nanocellulose, cleaved from native cellulose fibers, has extensively been explored because of its excellent mechanical, optical and thermal properties, combined with renewability. It can be used to fabricate composites, transparent films, fibers, porous foams and aerogels for diverse applications. This thesis focuses on utilizing native cellulose nanofibrils as building blocks for selected novel functional materials. Publication I addresses biomimetic nanocomposites, where the reinforcing hard cellulose nanofibrils form the majority of phases as separated by the soft rubbery block copolymeric domains. A facile ionic assembly is used to produce strong films with a promoted work-of-fracture showing a synergistic effect. This concept makes it possible to pursue biomimetic nanocomposites with further increased fracture toughness, while maintaining stiffness and strength. Publication II studies the mechanical and electrical properties of cellulose nanofibril and few-walled carbon nanotube hybrid aerogels. Incorporating carbon nanotubes with cellulose nanofibrils allows us to combine the attractive features of both components: wide availability, easy processing, and the sustainability of nanocellulose and the advanced electrical properties of carbon nanotubes. The concept demonstrates that hybrid aerogels could potentially be used in pressure sensing applications. Publication III further deals with the electrical behaviour of the above native cellulose nanofibril/carbon nanotube hybrid aerogels under repeated cyclic compression to explore "electrical fatigue". The hybrid aerogels can be constructed to allow stable reversible resistance changes in cyclic compression. Publication IV describes a nanocellulose film actuation with reversible bidirectional bending triggered by humidity. The films show a steady-state bending when exposed to humidity and then relaxed when removed from the imposed humidity continuously. The bending is highly sensitive to humidity, as demonstrated by its bending when exposed to a human hand at a distance of several millimeters. Such a film offers a facile route toward biomimetic actuation and novel types of active materials. In conclusion, cellulose nanofibrils are versatile building blocks in hybrid materials with block copolymers to tune the self-assemblies for mechanical properties, as templates for electroactive aerogels, and as films with new properties.Description
Supervising professor
Ikkala, Olli, Acad. Prof., Aalto University, Department of Applied Physics, FinlandKeywords
nanocellulose, native cellulose nanofibril, nanocomposite, biomimetic, carbon nanotube, aerogel, film, pressure sensing, actuation
Other note
Parts
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[Publication 1]: Wang, Miao; Olszewska, Anna; Walther, Andreas; Malho, Jani-Markus; Schacher, Felix H.; Ruokolainen, Janne; Ankerfors, Mikael; Berglund, Lars A.; Österberg, Monika; Ikkala, Olli. Colloidal Ionic Assembly between Anionic Native Cellulose Nanofibrils and Cationic Block Copolymer Micelles into Biomimetic Nanocomposites. Biomacromolecules 2011, 12, 2074-2081.
DOI: 10.1021/bm101561m View at publisher
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[Publication 2]: Wang, Miao; Anoshkin, Ilya V.; Nasibulin, Albert G.; Korhonen, Juuso T.; Seitsonen, Jani; Pere, Jaakko; Kauppinen, Esko I.; Ras, Robin H.A.; Ikkala, Olli. Modifying Native Nanocellulose Aerogels with Carbon Nanotubes for Mechanoresponsive Conductivity and Pressure Sensing. Advanced Materials 2013, 25, 2428-2432.
DOI: 10.1002/adma.201300256 View at publisher
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[Publication 3]: Wang, Miao; Anoshkin, Ilya V.; Nasibulin, Albert G.; Ras, Robin H.A.; Nonappa; Laine, Janne; Kauppinen, Esko; Ikkala, Olli. Electrical behavior of native cellulose nanofibril/carbon nanotube hybrid aerogels under cyclic compression. RSC Advances 2016, 6, 89051-89056.
DOI: 10.1039/C6RA16202A View at publisher
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[Publication 4]: Wang, Miao; Tian, Xuelin; Ras, Robin H.A.; Ikkala, Olli. Sensitive Humidity-Driven Reversible and Bidirectional Bending of Nanocellulose Thin Films as Bio-Inspired Actuation. Advanced Materials Interfaces 2015, 2, 1500080.
DOI: 10.1002/admi.201500080 View at publisher