Carbohydrate Polymers 104 (2014) 135–142 Contents lists available at ScienceDirect Carbohydrate Polymers j ourna l ho me page: www.elsevier.com/locate/carbpol Functionalized celluloses and their nanoparticles: Morphology, thermal properties, and solubility studies Priyanka R. Sharma, A.J. Varma ∗ Polymer Science & Engineering Division, CSIR-National Chemical Laboratory, Pune 411008, India a r t i c l e i n f o Article history: Received 3 December 2013 Received in revised form 4 January 2014 Accepted 4 January 2014 Available online 20 January 2014 Keywords: Cellulose 6-Carboxycellulose Nanoparticles DTG TGA Morphology a b s t r a c t Agricultural residues derived cellulose was used to synthesize a new series of carboxy functional- ized cellulosic nanoparticles (quasi-spherical shaped, 13.2–21.5% carboxyl content) and macro-sized 6-carboxycelluloses (long-fibril shaped, 1.7–22% carboxyl content). The DP (50–70) and yield (upto 46%) of nanoparticles were manipulated by controlling the reaction temperature and time. TGA/DTG thermographs of the carboxycelluloses gave thermostability data and co-related well with the residual crystalline, amorphous, and anhydroglucuronic acid content. The particle shape and size had no effect on the thermal stability. Some derivatives were fully or partially soluble in aqueous alkali and non-aqueous solvents, which can lead to increased versatility of these polymers. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction In recent years, deforestation concerns have led to the devel- opment of non-wood sources of cellulose, especially cellulose extracted from agricultural wastes such as sugarcane bagasse, wheat straw, rice straw, etc. (Nuruddin et al., 2011; Varma, 2013). This source of cellulose is considered environment-friendly, as fewer forest trees have to be cut to produce cellulose. Another major advancement in the field of cellulose chemistry and technol- ogy is the development of nanoparticles of cellulose and cellulose derivatives (Eichhorn, 2011; Kulterer et al., 2012; Nikolajaski, Wotschadlo, Clement, & Heinze, 2012). Since most of these cellulose and nanocellulose molecules are biocompatible and biodegradable, their role in several biomedical applications, biosensors, diagnostic molecular probes, drug delivery vehicles, etc. are being vigorously pursued, along with other exciting applications in biocomposites, membranes, electronics, and solar cells (Klemm, Heublin, Fink, & Bohn, 2005; Klemm et al., 2011; Lin, Huang, & Dufresne, 2012; Zhou et al., 2013). As in metal nanoparticles, research on nanocel- luloses has expanded to include shape-selective synthesis, such as nanofibres and nanospheres (Isogai, Saito, & Fukuzumi, 2011; Kulterer et al., 2012; Nikolajaski et al., 2012; Sharma & Varma, 2013). Graphene–cellulose paper membranes have been used as electrodes for flexible super capacitors. Celluloses have also been ∗ Corresponding author. Tel.: +91 20 25902178; fax: +91 20 25902618. E-mail addresses: aj.varma@ncl.res.in, aj.varma@yahoo.com (A.J. Varma). used with carbon nanotubes and combined with conducting poly- mers for the fabrication of electroconductive composites; further, hybrid inorganic–organic nanocomposites are emerging as a new class of functional nanomaterials (Lin et al., 2012; Shi, Philpis, & Yang, 2013). 6-Carboxycelluloses, prepared by oxidation of cel- lulose, have been extensively investigated for over seventy years due to their applications in wound dressing gauzes and several other related biomedical applications (Anderson & McIntyre, 1946; Houser, 1946; Kennedy, 1947; Scarff, Stookey, & Garcia, 1949). The earliest report on oxidation of cellulose to produce carboxylated cellulose was reported way back in 1883 (Cross & Bevau, 1883). Since then there have been regular streams of papers and patents on various methods of oxidation of cellulose and their applica- tions (Kumar & Yang, 2002; Nooy, Pagliaro, Bekkum, & Besemer, 1997; Okita, Saito, & Isogai, 2010; Shinoda, Saito, Okita, & Isogai, 2012; Yackel & Kenyon, 1942). In recent years, nanofibres of 6- carboxycelluloses have also been synthesized and their properties have been investigated (Crawford et al., 2012; Nachtkamp et al., 2012; Okita et al., 2010; Shinoda et al., 2012). Indeed, carboxy functionalized nanocelluloses can be expected to vastly expand the range of properties of electroconductive devices and biomedi- cal devices, where currently un-functionalized nanocelluloses are used. This was the motivation for taking up the synthesis and char- acterization of both macro-sized carboxycelluloses and nano-sized carboxycelluloses, and to compare their thermal properties, mor- phological changes in the products, and solubility characteristics. These are all key properties for fabricating new devices based on these materials. 0144-8617/$ – see front matter © 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carbpol.2014.01.015