Research groups
  • New cellulose derivatives

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00014 Helsingin yliopisto
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New cellulose derivatives

Cellulose is the most abundant natural polymer and a very promising raw material available at low cost for the preparation of various functional polymers. It has many attractive properties such as hydrophilicity, biocompatibility, biodegradable, stereoregularity, multichirality, reactive hydroxyl groups and the ability to form superstructure[1]. Although it has many useful properties it lacks the solubility and processability that most synthetic polymers possess. Before it can be used in polymer applications, cellulose needs to be modified, usually this involves reaction of the hydroxyl groups to give cellulose esters and ethers[1, 2]. Cellulose esters and ethers are used e.g. in coatings, films, membranes, controlled-release systems, and pharmaceuticals[2, 3].
However, the processing of the cellulose is complicated due to its very strong fibrillar structure. Using different kind of pretreatment methods e.g. chemical or enzymatic methods it is possible to increase the accessibility of cellulose to swelling and reactive agents and more controlled derivatisation is possible. To control the properties of cellulose the graft copolymerisation of a suitable monomer is a useful technique for cellulose modification. Traditionally, free radical polymerisation is used to graft vinyl monomers from cellulose backbone but this method allows no control over the molecular weight and molecular weight distribution of the grafts. The overall goal of our group is to prepare new derivatives from wood cellulose and from cellulose derivatives with controlled chemical and supramolecular structure. The grafting of cellulose and its derivatives will be realized by ‘grafting-from’ technique using controlled radical polymerisation methods that allow tailoring the length and the structure of the grafts. CMC (carboxymethyl cellulose), EHEC (ethyl hydroxyethyl cellulose) and pretreated cellulose have been used as a starting materials to prepare the new graft copolymers based on a cellulose backbone[4, 5].

The project is part of the larger projects at first of NewCell (New cellulose derivatives from wood for high value products) [6] and later on ReCell (Refined cellulose derivatives for high-value biomedical products), in which the accessibility of wood cellulose towards more homogeneous substitution and otherwise derivatives with new functionalities and thereafter towards more sophisticated end uses will be developed. The target products are high value products e.g. pharmaceutical and fine chemical applications, as well as fibres, coatings, casings, sponges and beads.

The other research project related to cellulose deals with heterogeneous modification of cellulose. Heterogeneous cellulose modification does not require fiber dissolving, but the modification reaction take place at the surfaces of cellulose fibers. The aim of our group is to modify cellulose heterogeneously, not to modify the structure of cellulose at molecular level, and to capsulate this modified cellulose. The advantage of surface modification is the improved interaction between the polymer and cellulose leading to better mixing of the components. Microcrystalline cellulose and nanocellulose are encapsulated inside a polymer matrix to improve the mechanical properties of polymer composites or films and the properties of these nanocomposites are studied.

  1. 1)    Heinze, T. and Liebert, T. Prog. Polym. Sci. 2001, 26, 1689-1762.
  2. 2)    Edgar K. J.; Buchanan C.M.; Debenham J. S.; Rundquist P.A.; Seiler B. D.; Shelton M.C. and Tindall D. Prog. Polym. Sci. 2001, 26, 1605-1688.
  3. 3)    Klemm, D; Heublein, B.; Fink, H.-P. and Bohn, A. Angew. Chem. Int. Ed. 2005, 44, 3359-3393.
  4. 4)    M. Hiltunen, S.L. Maunu and H. Tenhu, 13th International Symposium on Wood, Fibre and Pulping Chemistry (ISWFPC), 2005, Auckland, New Zealand, Proceedings, Vol. 3.,  p.143-146.
  5. 5)    M. Hiltunen and S.L. Maunu, 14th International Symposium on Wood, Fibre and Pulping Chemistry (ISWFPC), 2007, Durban, South Africa, Proceedings CD.
  6. 6)    S. Karlsson, in Wood Material Science and Engineering Final Report Finnish-Swedish Research Programme 2003-2007: New Cellulose Derivatives from Wood for High Value Products, 2007, 138-155.