PHASE TRANSITION AND RHEOLOGICAL BEHAVIORS OF CONCENTRATED CELLULOSE/IONIC LIQUID SOLUTIONS
The phase transition and rheological behaviors of concentrated solutions of microcrystalline cellulose (MCC) in an ionic liquid of 1-allyl-3methylimidazolium chloride (AMIMC1) have been investigated. The optical microscope observations and DSC measurements coherently indicate that the two critical cellulose concentrations of appearances of biphase and fully anisotropic phase for the MCC/AMIMC1 solutions are 9 and 16 wt%, respectively (see Figs. 1 and 2). From the oscillatory shear measurements it is found that the crossover frequency first moves to lower values and then moves back to higher values with increasing cellulose concentration, which indicates that most cellulose chains can be aligned or orientated to reduce chain entanglements when the cellulose concentration is above 14 wt%. From the steady shear measurements it is surprisingly found that the viscosity versus shear rate curves exhibit four flow regions including two plateaus and two shear-thinning regions when the cellulose concentration exceeds 9 wt% (see Fig. 3). The influences of cellulose concentration and temperature on the first normal stress differences (N1) are analyzed according to the Larsons theory. It is found that the peak of N1 always appears at intermediate of the first shear-thinning region and the following minimum of N1 appears at onset of the second shear-thinning region. The viscosity versus shear rate curves only exhibit two flow regions when temperature is above respective T_c, meanwhile negative N1 values disappear and N1 increases monotonically. The above results suggest that melting of the liquid crystal domains at high temperature results in disappearance of the second plateau for the viscosity versus shear rate curves.
Hongzan Song Yanhua Niu Zhigang Wang
CAS Key Laboratory of Engineering Plastics, Beijing National Laboratory for Molecular Sciences, Inst CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, Hefei Na
国际会议
PP’2010，Jinan International Symposium on Polymer Physics(2010济南国际高分子物理学术研讨会)
济南
英文
305-306
2010-06-06（万方平台首次上网日期，不代表论文的发表时间）