A new type of cellulose nanoparticle invented by McGill University researchers could provide a more effective and less environmentally damaging solution to the buildup of scale.

In a series of papers published in the Royal Society of Chemistry’s Materials Horizons and the American Chemical Society’s Applied Materials & Interfaces, a team of McGill chemists and chemical engineers describe how they have developed a phosphorus-free anti-scaling solution based on a nanotechnology breakthrough: hairy nanocellulose.

Lead author of the paper, Overcoming Interfacial Scaling Using Engineered Nanocelluloses: A QCM-D Study, Amir Sheikhi, now a postdoctoral fellow in the Department of Bioengineering at the University of California, Los Angeles, said that despite its green credentials cellulose was not an obvious place to look for a way to fight scale.

“Cellulose is the most abundant biopolymer in the world. It’s renewable and biodegradable. But it’s probably one of the least attractive options for an anti-scaling agent, because it’s neutral—it has no charged functional groups,” he said.

Hairy nanocellulose, used as an anti-scaling agent in the container at right, prevents the kind of mineral build-up that is restricting outflow from the container at left. Image and caption credit: McGill University.

While working as a postdoctoral fellow with McGill chemistry professor Ashok Kakkar, Sheikhi developed a number of macromolecular antiscalants that were more effective than products widely used in industry, but all of his discoveries were phosphonate-based. His desire to push his research further and find a phosphorus-free alternative led him to take a closer look at cellulose.

“Nanoengineered hairy cellulose turned out to work even better than the phosphonated molecules,” he said.

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The breakthrough came when the research team succeeded in nanoengineering negatively charged carboxyl groups onto cellulose nanoparticles. The result was a particle that was no longer neutral. Instead, it carried charged functional groups capable of controlling the tendency of positively charged calcium ions to form scale.

Previous attempts to functionalize cellulose in this way focused on two earlier nanoparticle forms: cellulose nanofibrils and cellulose nanocrystals. But these efforts produced only a minimal amount of useful product. The McGill team’s work with hairy cellulose took advantage of the new nanoparticle, first discovered in the laboratory of McGill chemistry professor Theo van de Ven.

Van de Ven, who also participated in the anti-scaling research, recalled the moment in 2011 when Han Yang, then a doctoral student in his lab, stumbled upon the new form of nanocellulose.

The secret to making hairy nanocellulose lies in cutting cellulose nanofibrils, made up of an alternating series of crystalline and amorphous regions, at precise locations to produce nanoparticles with amorphous regions sprouting from either end like strands of hair.

“By breaking the nanofibrils up the way we do, you get all these cellulose chains sticking out which are accessible to chemicals,” van de Ven said. “That’s why our nanocellulose can be functionalized to a far greater extent than other kinds.”

Given the chemical versatility of hairy nanocellulose, the research team sees strong potential for applications beyond anti-scaling, including drug delivery, antimicrobial agents, and fluorescent dyes for medical imaging.

“We can link just about any molecule you can think of to hairy nanocellulose,” said van de Ven.

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