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2005年03月03日

【期刊论文】Studies on the Critical Phase-Transition Behavior of Cholesteric N-Phthaloyl Chitosan/Dimethyl Sulfoxide Solutions by Five Techniques

董炎明， Yusong Wu， *， Yanming Dong， Hua Zhou， Yonghong Ruan， Huiwu Wang， Yaqing Zhao

Journal of Applied Polymer Science, Vol. 90, 583-586 (2003)，-0001，（）：

-1年11月30日

摘要

A selectively side-modified chitosan derivative, N-phthaloyl chitosan (PhthCs), was prepared. Five techniques, including circular dichroism (CD) spectropolarimetry, ultraviolet-visible (UV-vis) spectroscopy, small-angle light scattering (SALS), polarized optical microscopy (POM), and differential scanning calorimetry (DSC), were simultaneously applied to investigate the order-disorder phase transition for the lyotropic PhthCs/dimethyl sulfoxide system. POM observations suggested that the critical concentration was 48w%, which agreed well with the DSC measurements. A four-leaf SALS picture was recorded in biphasic solutions. The four-leaf type became a circular symmetric scattering picture with a further increase in the concentration. A sharp peak at 330 nm was recorded in dilute isotropic solutions with CD measurements. The sharp peak turned into a broad tailed peak from 330 to 800nm after the phase transition occurred. The sharp peak was induced by a chromophore (phthoyl group). The broad peak was attributed to the formation of short-range-ordered organization in the concentrated solutions. In UV-vis studies, when the system varied from isotropic to anisotropic, the absorption band turned into platform. These five techniques were proven to be feasible methods for measuring the phase transition of cholesteric liquid crystals.

UV-vis spectroscopy， differential scanning calorimetry (， DSC)，， solution properties

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2005年03月03日

【期刊论文】Multiple crystalline morphologies of N-Alkyl chitosan solution cast films

董炎明， Yanming Dong， Kensuke Sakurai， Yusong Wu， and Yukie Kondo

Polymer Bulletin 49, 189-195 (2002)，-0001，（）：

-1年11月30日

摘要

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2005年03月03日

【期刊论文】Studies on Lyotropic Liquid-Crystalline N-Alkyl Chitosans in Formic Acid

董炎明， Yusong Wu， Yanming Dong， *， Ling Chen， Jianying Huang， Jun Li

Macromol. Biosci. 2002, 2, 131-134，-0001，（）：

-1年11月30日

摘要

biopolymers， chitosan， critical concentration， degree of substitution， liquid-crystalline polymers (， LCP)，， lyotropic

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2005年03月03日

【期刊论文】Influence of degree of N-butyrylation on critical concentration of N-butyrylated chitosan/dichloroacetic acid liquid crystalline solution

董炎明， Yanming Dong， Congyi Xu， Jianwei Wang， Yusong Wu， Yonghong Ruan， Mian Wang

Polymer Bulletin 45, 495-500 (2001)，-0001，（）：

-1年11月30日

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2005年03月03日

【期刊论文】Influence of degree of molar etherification on critical liquid crystal behavior of hydroxypropyl chitosan

董炎明， Yanming Dong*， Yusong Wu， Jianwei Wang， Mian Wang

European Polymer Journal 37(2001)1713-1720，-0001，（）：

-1年11月30日

摘要

Hydroxypropyl chitosan (HPCS) with different degree of molar etherification (DME, from 0.6 to 6.0) were synthesized and characterized by FTIR, 1H-NMR and elemental analysis. The effect of DME on critical concentration forming lyotropic liquid crystal (C*) was investigated in three solvents (formic acid, dichloroacetic acid and water). C* increased as DME raised but presented a platform at low DME (less than about 2.6), which was explained based on both the amount and the size of flexible substituents. HPCS with DME ≥3.2 were water soluble. C* of HPCS aqueous solutions were evidently lower than those of formic acid or dichloroacetic acid solutions. Typical cholesteric texture appeared in HPCS solutions of all three solvents at proper concentrations.

Chitosan， Hydroxypropyl chitosan， Lyotropic liquid crystal， Degree of molar etherification， Critical concentration， Cholesteric texture

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