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Title of the thesis: Reactivity and accessibility of cellulose in cold alkali dissolution: Effects of hornifying, acidic, and mercerizing pretreatments.

Thesis defender: Antti Koistinen 
Opponent: Prof. Juha Fiskari, Mid Sweden University 
Custos: Associate prof. Thaddeus Maloney, Aalto University School of Chemical Engineering

Reactivity and accessibility of cellulose in cold alkali dissolution: Effects of hornifying, acidic, and mercerizing pretreatments.

Cellulose is widely seen as one of the most promising renewable feedstocks for replacing fossil-based resources in textiles, packaging, and advanced materials. Yet one major challenge remains: cellulose is naturally resistant to dissolution and chemical modification. This resistance limits the efficiency of many sustainable processing technologies.

This doctoral research examines how cellulose modification alters its dissolution in cold aqueous sodium hydroxide: an inexpensive and industrially attractive solvent system. Improving this process could help enable more sustainable manufacturing of man-made cellulosic fibres and other bio-based materials.

The study focuses on how different pretreatments – acidic treatment, alkaline treatment (mercerization), and drying-induced hornification – change the accessibility and reactivity of cellulose fibres. These processes alter the cellulose fibre structure and influence how readily it participates in chemical reactions.

The results reveal a key new insight that accessibility and reactivity. Alkaline pretreatment makes cellulose fibres more open and porous, which would seem beneficial. However, the research showed that this increased accessibility actually reduced the fibre’s chemical reactivity in cold alkali dissolution. In contrast, acid treatment improves dissolution mainly by shortening cellulose chains, making them easier to process – without significantly changing fibre swelling.

Unexpectedly, drying-induced structural changes (hornification), often considered harmful, were found to improve solubility in the alkali solvent.

These findings challenge common assumptions about how cellulose should be pretreated for dissolution. They show that making fibres more “open” does not necessarily make them more reactive – and that different structural modifications affect processing in fundamentally different ways.

The results provide new guidance for designing more efficient and resource-wise cellulose processing routes. This knowledge can support the development of next-generation textile fibres and other sustainable cellulose-based products, helping reduce reliance on fossil materials.
 

cellulose dissolution; cold alkali dissolution; hornification; reactivity and accessibility 

Thesis available for public display 7 days prior to the defence at .

Contact information: antti.koistinen@aalto.fi