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Abstract  

The thermal and thermooxidative behavior of sodium salt of hyaluronic acid (HA) and its n-hexyl, n-decyl, n-tetradecyl and n-hexadecyl ether derivatives having an equal degree of substitution have been studied by means of differential scanning calorimetry (DSC) and thermogravimetry (TG). Derivatives were prepared by a substitution of H atom at the OH bound to the sixth C of N-acetyl-D-glucosamin of HA unit by n-hexyl, n-decyl, n-tetradecyl and n-hexadecyl chains. Both thermal and thermooxidative degradation of HA and derivatives resulted in multistep process. The main interest of this work was focused on processes occurring in the course of the first decomposition step. Experimental DSC data showed lower stability of derivatives and, remarkably lower heat evolution in comparison with original HA. On the other hand, TG measurement recorded lower mass loss for derivates which indicated appearance of new types of crosslinking reactions. Oxidative stability was evaluated by means of DSC that provided the induction period and the protection factor determination. Derivates showed remarkably lower stability in comparison with original HA; comparing each other, the highest oxidation stability showed n-decyl and n-tetradecyl derivates.

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thermooxidative degradation possess both practical and scientific significance. Also a possible interaction between the active substance and different excipients is relevant for the establishment of dosage forms. The decomposition reaction of

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-oxidation [ 1 – 3 ]. In a previous paper [ 4 ], it was proved the importance of an elaborated kinetic analysis of the thermooxidative degradation for the selection of an appropriate stabilizer. Also, in a recent paper [ 5 ], a synergetic effect by using

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Journal of Thermal Analysis and Calorimetry
Authors: F. M. Aquino, D. M. A. Melo, R. C. Santiago, M. A. F. Melo, A. E. Martinelli, J. C. O. Freitas, and L. C. B. Araújo

. 5. Genieva , SD , Vlaev , LT , Atanassov , AN 2010 Study of the thermooxidative degradation kinetics of poly(tetrafluoroethene) using iso-conversional calculation procedure . J Therm Anal Calorim 99 : 551 – 561 10

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flow rate of 90 mL min −1 . The thermal and thermooxidative degradation of polymeric materials is a complex process involving successive and/or parallel steps. Nevertheless the kinetic analysis of non-isothermal thermogravimetric data is

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Journal of Thermal Analysis and Calorimetry
Authors: Zuzana Cibulková, Andrea Černá, Peter Šimon, Ján Uhlár, Karol Kosár, and Peter Lehocký

has been tested in diene elastomers [ 4 ]. In our previous papers, the effect of p -phenylenediamines in preventing thermooxidative degradation of polyisoprene rubber [ 5 , 6 ] has been investigated by non-isothermal DSC measurements. DSC

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. 10. Peterson , JD , Vyazovkin , S , Wight , CA . Kinetics of the thermal and thermooxidative degradation of polystyrene, polyethylene and polypropylene . Macromol Chem Phys . 2001 ; 202 : 775 – 784 . 10

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polyphenylene ether . Polym Degrad Stab . 2003 ; 79 : 29 – 36 . 10.1016/S0141-3910(02)00235-5 . 6. Vrandečić , NS , Klarić , I , Kovačić , T . Thermooxidative degradation of poly

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-6031(98)00413-4 . 33. Salla , JM , Morancho , JM , Ramis , X , Cadenato , A 2005 Isothermal degradation and thermooxidative degradation of an epoxy powder coating . J Therm Anal Calorim 80 1 163 – 169 10.1007/s10973

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.01.013 . 16. Genieva , SD , Vlaev , LT , Atanassov , AN . Study of the thermooxidative degradation kinetics of poly(tetrafluoroethene) using iso-conversional calculation procedure . J Therm Anal Calorim 2010 99 : 551 – 561 10

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