Abstract : methanesulfonic acid method was used to prepare five acylated chitins . except heptanoyl chitin , four of them , i . e . acetyl chitin , propionyl chitin , butyryl chitin and hexanoyl chitin , had high degree of substitution ( from 1 . 5 to 2 . 0 ) and exhibited lyotropic liquid crystalline behavior and cholesteric phase . as the length of the side chain increased the critical concentration ( w / w ) somewhat increased from 0 . 21 to 0 . 26 because the chain rigidity dropped . the critical concentration values of all the four derivatives were much higher than that of chitin ( 0 . 12 ) due to the decrease of intramolecular hydrogen bonds . the four acylated chitin can form typical banded texture after being sheared . there minimum concentrations to form banded texture of them were evidently different , varied from 0 . 25 ( for acetyl chitin ) to 0 . 37 ( for hexanoyl chitin ) . these results further indicated that liquid crystallinity decreased while the length of flexible side substituents increased 文摘:四种羧酰化甲壳素即乙酰化、丙酰化、丁酰化和己酰化甲壳素在二氯乙酸溶液中均呈现胆甾型溶致液晶相.临界浓度随侧基长度增加而略有增加，衍生物的临界浓度明显都比原甲壳素高许多，这些规律都可以用链刚性的变化来解释.四种羧酰化甲壳素在剪切时均能形成条带织构，而且能形成条带织构的最低浓度有明显差别，随侧基长度增加而提高，进一步表明侧基较长，液晶性减少
