Liudvinaviciute Dovile, Rutkaite Ramune, Bendoraitiene Joana, Klimaviciute Rima
Department of Polymer Chemistry and Technology, Kaunas University of Technology, Radvilenu Rd. 19, LT-50254 Kaunas, Lithuania.
Department of Polymer Chemistry and Technology, Kaunas University of Technology, Radvilenu Rd. 19, LT-50254 Kaunas, Lithuania.
Carbohydr Polym. 2019 Oct 15;222:115003. doi: 10.1016/j.carbpol.2019.115003. Epub 2019 Jun 19.
Thermal behaviour and stability of chitosan (CH) and phenolic acids complexes could be of high importance in regard both the practical applications and understanding the complex formation. Thermal degradation of insoluble complexes of CH and caffeic (CACH) or rosmarinic acid (RACH) was investigated in air and nitrogen atmosphere. Thermal decomposition of CACH proceeded in two stages, first of which was attributed to decarboxylation of adsorbed CA in the temperature interval from 150 °C to 200 °C, and second one was related to decomposition of CH backbone at temperatures higher than 200 °C. Thermal degradation of RACH proceeded in one stage at temperatures higher than 200 °C, in the broad temperature range and was related to decomposition of formed complex. Values of apparent activation energy (E) related to the second stage of thermal decomposition of CACH and decomposition of RACH at conversion values (α) from 0.1 to 0.8 were determined by using Flynn-Wall-Ozawa method. For CACH the dependence between E and α was very similar to that of CH and showed that products of CA thermal degradation formed in the first stage didn't influence the thermal degradation of CACH in the second stage. Meanwhile, for RACH, initially, values of E increased with an increase of conversion degree, at certain value of α reached the maximum which depended on the RA to CH molar ratio, and then decreased.
壳聚糖（CH）与酚酸复合物的热行为和稳定性对于实际应用以及理解复合物的形成都可能极为重要。研究了CH与咖啡酸（CACH）或迷迭香酸（RACH）的不溶性复合物在空气和氮气气氛中的热降解情况。CACH的热分解分两个阶段进行，第一阶段归因于吸附的CA在150℃至200℃温度区间内的脱羧作用，第二阶段与温度高于200℃时CH主链的分解有关。RACH的热降解在温度高于200℃时于较宽温度范围内分一个阶段进行，且与形成的复合物的分解有关。通过Flynn-Wall-Ozawa方法确定了与CACH热分解第二阶段以及RACH在转化率（α）从0.1至0.8时分解相关的表观活化能（E）值。对于CACH，E与α之间的依赖关系与CH的非常相似，表明第一阶段形成的CA热降解产物对第二阶段CACH的热降解没有影响。同时，对于RACH，起初，E值随转化率的增加而增加，在α的某一特定值时达到最大值，该最大值取决于RA与CH的摩尔比，然后下降。
