Available online at www.pelagiaresearchlibrary.com Pelagia Research Library Advances in Applied Science Research, 2015, 6(2):141-149 ISSN: 0976-8610 CODEN (USA): AASRFC 141 Pelagia Research Library Synthesis and characterization of N-alkylchitosan as well as its potency as a paper coating material Hasna Tazkia Nikmawahda 1 , Purwantiningsih Sugita 2* and Budi Arifin 2 1 Department of Chemistry Graduate Student, Bogor Agricultural University, Bogor, West Java, Indonesia 2 Department of Chemistry, Bogor Agricultural University, Bogor, West Java, Indonesia ______________________________________________________________________________________________ ABSTRACT N-Alkylchitosan is an amphiphilic chitosan’s derivative. Its alkyl side chain is hydrophobic and will reduce the water-absorption capacity of the hydrophilic chitosan. Therefore, it can be applied as waterproof paper coating in food packaging paper. In this study, N-alkylchitosan is synthesized from commercial chitosan having 86% deacetylation degree. Two synthetic methods were compared, in heterogenous system using suspended chitosan in methanol and homogenous system where chitosan was dissolved in 1% acetic acid at the first stage. The infrared spectra showed that synthesis conducted in homogenous system successfully synthesized N-octylchitosan. The degree of substitution (DS) value of the N-octylchitosan was 0.16, based on proton nuclear magnetic resonance analysis. Derivatives with longer alkyl side chain (N-decyl and N-dodecylchitosan) exhibited much lower DS, that is 0.02, which is predicted as the effect of increased steric hindrance. Therefore, based on this study, N-octylchitosan is the most potential as a waterproof paper coating because it has the highest value of DS. Key words: chitosan, degree of substitution, N-octylchitosan, paper coating. ______________________________________________________________________________________________ INTRODUCTION Paper is composed of cellulose fiber having a lot of hydroxyl functional group so it can absorb water from environment. This property will decrease its mechanical and physical strength, particularly in some application requiring paper properties as a barrier, as in food packaging paper. Therefore, to repair this property, paper is generally combined by varieties of coating material such as plastic or aluminium. Synthetic polymer such as polyethylene and polyamide, respectively can increase waterproof property and can decrease vapor transmission rate. Yet, commonly this synthetic polymer is difficult to be recycled and decomposed [1]. Renewable biopolymer- base coating is already developed nowadays since it is not toxic, easy to be decomposed and recycled. Chitosan is a second biggest biopolymer in nature after cellulose and is obtained as deacetylation product of N- acetyl-D-glucosamine residue in chitin by using base [2]. Chitosan is not toxic, easy to be decomposed, biocompatible, and also has antibacterial property. Chitosan, because of its hydrophilic property, was used as coating and additive in paper making to increase resistivity to gas and oil [3]. Chitosan modification to N- alkylchitosan will give chitosan derivative which is amphiphilic since it has both hydrophilic and hydrophobic chain. The hydrophobic chain of N-alkylchitosan will decrease chitosan water-absorption capacity [4], so it can be used as waterproof coating in food packaging paper [5]. N-Alkylchitosan can be synthesized through reductive amination procedure. Primary amino group in chitosan form Schiff base with aldehyde and the secondary imine formed is reduced by sodium borohydride (NaBH 4 ) [6, 7, 8, 9, 10, 11] or the other reducing agent such as sodium cyanoborohydride (NaBH 3 CN) [5,12], and potassium borohydride (KBH 4 ) [13, 14] to be N-alkylchitosan (Figure 1). Alkyl chain variation of N-alkylchitosan was tested by Nicu et al. [4] in paper coating application. Treating with 3 kinds of aldehyde, that is octanal, decanal, and dodecanal gave N-alkylchitosan with alkyl degree of substitution (DS), respectively 0.0374, 0.0351, and 0.0335. N-