Please cite this article in press as: Ferreira, R., et al., Isolation of suberin from birch outer bark and cork using ionic liquids: A new source of macromonomers. Ind. Crops Prod. (2012), http://dx.doi.org/10.1016/j.indcrop.2012.10.002 ARTICLE IN PRESS G Model INDCRO-6363; No. of Pages 8 Industrial Crops and Products xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect Industrial Crops and Products journa l h o me page: www.elsevier.com/locate/indcrop Isolation of suberin from birch outer bark and cork using ionic liquids: A new source of macromonomers Rui Ferreira a,1 , Helga Garcia a,1 , Andreia F. Sousa b , Carmen S.R. Freire b , Armando J.D. Silvestre b , Luís Paulo N. Rebelo a , Cristina Silva Pereira a,c,∗ a Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal 2 b CICECO and Department of Chemistry, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal c Instituto de Biologia Experimental e Tecnológica (IBET), Apartado 12, 2781-901 Oeiras, Portugal a r t i c l e i n f o Article history: Received 27 July 2012 Received in revised form 24 September 2012 Accepted 3 October 2012 Available online xxx Keywords: Suberin Cork Birch outer bark Cholinium hexanoate ionic liquids a b s t r a c t Cholinium hexanoate, a biocompatible and biodegradable ionic liquid, was recently demonstrated to efficiently and selectively extract suberin domains from cork, combining high extraction efficiency with isolation of a partial depolymerised material. In the present paper, we report a comparative study of the characterisation of suberin extracted from birch outer bark and from cork using cholinium hex- anoate. It became apparent that both extracted suberin samples showed still a cross-linked nature, i.e. likely to be closely related to in situ suberin. Suberin samples were mainly constituted by oligomeric or polymeric structures in turn essentially composed by long chain hydroxyacids monomers. Their high thermal stability together with the oligomeric/polymeric nature, open new perspectives for suberin use as macromonomers in the development of bio-based polymeric materials. This also contributes for the valorisation of suberin rich agro-forest residues. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Knowledge on natural polymers, such as starch, cotton, proteins and wool, is ancient and originated in the 19th century (Sperling, 2006; Gandini, 2011). During the last decade, we have been wit- nessing a renewed and exponential increase of interest in the production of chemicals, materials, fuels and energy obtained from renewable resources. This is especially true in the so-called biore- finery concept (Kamm et al., 2000; Mosier et al., 2005), which involves, in many cases, application of valuable components from by-products of agro-forest industries, such as suberin from cork residues. Suberin, a complex aromatic–aliphatic cross-linked biopolyester, is widespread in the plant Kingdom but it is particularly abundant in Quercus suber L. cork (30–50 wt%) and Betuta pendula outer bark (40–50 wt%) (Pereira, 1988; Lopes et al., 2000a,b, 2001; Gandini et al., 2006; Pinto et al., 2009). This hydrophobic biopolyester plays a key role as a protective barrier ∗ Corresponding author at: Instituto de Tecnologia Química e Biológica, Universi- dade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal. Tel.: +351 211157786. E-mail address: spereira@itqb.unl.pt (C. Silva Pereira). 1 Equally contributing authors. 2 http://www.itqb.unl.pt between the plant and the environment (Pollard et al., 2008). Suberin constitutes a major natural source of valuable compounds such as -hydroxyacids, ,-dicarboxylic acids and corresponding mid-chain epoxy or dihydroxy derivatives (Gandini et al., 2006; Pinto et al., 2009). These compounds have attracted considerable attention as building blocks for polymer synthesis (Gandini et al., 2006; Olsson et al., 2007; Sousa et al., 2008, 2011). Wastes derived from birch kraft pulp mills and cork industries are produced in large amounts, corresponding to ∼3.4 wt% (Ekman, 1983; Paper and wood insights, 2006) and ∼23 wt% (Gil, 1988) of the total production, respectively. Up to present, their exploitation is often limited to burning in biomass boilers to produce energy. However, substantial valorisation can be attained if valuable com- ponents are extracted prior to burning. Suberin can be isolated from cork and birch outer bark residues by a set of well defined depolymerisation methodologies. They normally require harsh chemical processes of ester bond cleavage through alkaline methanolysis with sodium methoxide, or by aque- ous alkaline hydrolysis (Ekman and Eckerman, 1985; Gandini et al., 2006). Suberin partial depolymerisation can also be achieved using more gentle (though less efficient) extraction processes, e.g. cal- cium oxide methanolysis (Grac ¸ a and Pereira, 1997, 1999, 2000a,c). Advances in suberin extraction under milder and environmen- tally benign conditions will certainly foster its wider application. Recently it has been demonstrated that extraction of suberin from cork can also be attained using cholinium hexanoate as solvent 0926-6690/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.indcrop.2012.10.002