Role of the alkyl moiety and counter ions on the thermal stability of chitosan derivatives

Abstract

The thermal stability of alkyl chitosan derivatives (RChi) and N,N,N-trimethyl chitosan bearing different counter ions (TMCX) was assessed by means of TG analyses. Multistep TG curves were observed for TMCX regardless of the counter ion. They exhibited lower DTG peak temperatures (TMCCl/ 238.2 C, TMCBr/224.5 C, TMCI/222.6 C, and TMC-SO 4 /237.0 C) as compared to the parent chitosan (306.4 C) while, in contrast, the RChi showed higher DTG temperatures (ButChi/311.7 C, OctChi/327.8 C,and DodecChi/306.3 C). The apparent activation energy values determined by using the isoconversional method revealed that the RChi derivatives have low activation energy (OctChi/111.6 6 5 kJ/mol), whereas quaternary salts have high activation energy (TMCI/ 155.5 6 10 kJ/mol). V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: [815][816][817][818][819][820][821][822] 2011