Modification of crystallinity and pore size distribution in coagulated cellulose films
2013 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 4, 1657-1667 p.Article in journal (Refereed) Published
In this study the effects of altering the coagulation medium during regeneration of cellulose dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate, were investigated using solid-state NMR spectroscopy and NMR cryoporometry. In addition, the influence of drying procedure on the structure of regenerated cellulose was studied. Complete conversion of the starting material into regenerated cellulose was seen regardless of the choice of coagulation medium. Coagulation in water predominantly formed cellulose II, whereas coagulation in alcohols mainly generated non-crystalline structures. Subsequent drying of the regenerated cellulose films, induced hornification effects in the form of irreversible aggregation. This was indicated by solid-state NMR as an increase in signal intensity originating from crystalline structures accompanied by a decrease of signal intensity originating from cellulose surfaces. This phenomenon was observed for all used coagulants in this study, but to various degrees with regard to the polarity of the coagulant. From NMR cryoporometry, it was concluded that drying induced hornification generates an increase of nano-sized pores. A bimodal pore size distribution with pore radius maxima of a few nanometers was observed, and this pattern increased as a function of drying. Additionally, cyclic drying and rewetting generated a narrow monomodal pore size pattern. This study implies that the porosity and crystallinity of regenerated cellulose can be manipulated by the choice of drying condition.
Place, publisher, year, edition, pages
2013. Vol. 20, no 4, 1657-1667 p.
Crystallinity, NMR cryoporometry, Porosity, Regenerated cellulose, Solid-state NMR
Paper, Pulp and Fiber Technology
IdentifiersURN: urn:nbn:se:kth:diva-132213DOI: 10.1007/s10570-013-9982-7ISI: 000322673000011ScopusID: 2-s2.0-84881030017OAI: oai:DiVA.org:kth-132213DiVA: diva2:659260
QC 201310242013-10-242013-10-242014-01-22Bibliographically approved