To modify its properties, cellulose sheets were either dipped in (or covered with) solvent solutions of ethyl-2 cyanoacrylate (ECA) monomer.
ECA is polymerized in the presence of hydroxyl (-OH) groups, to form poly-ethyl cyanoacrylate (PECA), a glue-like material. This caused the formation of a layer of PECA on the surface of each cellulose filament; as a consequence, the cellulose sheet became waterproof. The image to the left of this paragraph demonstrates this property, with water drops on the surface of the paper, not being adsorbed. All the other characteristics of the paper, such as color and size or thickness, were not affected by this treatment.
Additional Properties Of Treated Cellulose
To give cellulose additional properties, in some cases the solutions used also contained other specific compounds in form of nano or submicron particles; hence, both the ECA and the particles were adsorbed by the cellulose.
The particles, and the functionalities induced by their presence, are listed below:
- Water-resistant paper: By using polytetrafluoroethylene (PTFE), or wax, they obtained a hydrophobic cellulose sheet; the value of the contact angle was as high as 160o (superhydrophobic material). This is because both PTFE and wax are hydrophobic themselves.
- Magnetic paper: By adding MnFe2O4, due to the magnetic behavior of the nanoparticles, the cellulose sheet showed magnetic properties. This can be seen in the picture above, where the paper is attracted towards a magnet.
- Antibacterial paper: With the addition of (Ag) nanoparticles, which are well known for their antibacterial activity, the cellulose showed antibacterial properties too – the viability of E. coli bacterial strain decreased to 20% in comparison with standard paper.
- Glowing paper: Adding CdSe/ZnS, compounds that are Quantum Dots (QDs), created a paper that showed light emission in a specific region of the visible spectrum. When included in the cellulose, these particles also showed a narrow and sharp emission peak localized at l of about 580 nm.
Changing Paper Properties: Simple but Effective
Dr. Athanassia Athanassiou, leading scientist of this study, explained to Decoded Science:
“The process we developed is new, simple, one-step, and it can be easily scaled up for industrial applications. It is also important to note that this process is not performed during the cellulose sheet fabrication but it is applied on the finished product. Moreover, using the same approach, we can give to the cellulose completely different properties, depending on the fillers we use. Potentially, this process could be applied using different nano or submicron particles, and give different functionality.”
Changing the World: One Sheet of Paper at a Time
Making these simple changes to paper may provide advances in multiple fields of study, as well as many industries. As Dr. Athanassiou told us, “Waterproof cellulose with these properties can really have many potential applications in different branches of technology – from waterproof antibacterial paper, to preserving important documents, to hydrophobic films for food packaging; the potential is tremendous.”
Fragouli D. et al., Superparamagnetic cellulose fiber networks via nanocomposites functionalization. (2012). J. Materials Chemistry, 22, 1662. Accessed May 10, 2012.
Cingolani R. et al., Modulating antibacterial properties using nanotechnology. (2012). Nanomedicine 6(9), 1483. Accessed May 10, 2012.
Bayer I.S. et al., Water-Repellent Cellulose Fiber Networks with Multifunctional Properties. (2011). Applied Materials Interfaces, 3, 4024. Accessed May 10, 2012.
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