Shear banding or not in entangled DNA solutions depending on the level of entanglement

被引:66
作者
Boukany, Pouyan E. [1 ]
Wang, Shi-Qing [1 ]
机构
[1] Univ Akron, Dept Polymer Sci, Akron, OH 44325 USA
基金
美国国家科学基金会;
关键词
biochemistry; biomechanics; biorheology; creep; DNA; elastic moduli; molecular biophysics; shear flow; velocimeters; POLYMER-SOLUTIONS; CONSTRAINT RELEASE; STRESS OVERSHOOT; HIGH-RATES; BEHAVIOR;
D O I
10.1122/1.3009299
中图分类号
O3 [力学];
学科分类号
08 ; 0801 ;
摘要
Entangled DNA solutions are ideal as a model system to examine nonlinear shear flow behavior. Even when the number of entanglements per chain, Z, is higher than 100, the solution is still soft enough with an elastic plateau modulus under 100 Pa and is thus amenable to experimental study by commercial rotational rheometry without ambiguity and uncertainty. We have investigated nonlinear flow behavior of three entangled DNA solutions with Z=24, 60, and 156, respectively, using a combination of particle-tracking velocimetric (PTV) and conventional rheometric measurements. We explore questions such as (a) whether shear banding also occurs in moderately entangled solutions, (b) whether creep results in development of nonlinear velocity profile, (c) whether shear banding produced in startup shear and creep persists at long times in steady state, and (d) whether these entangled solutions exhibit homogeneous shear at the upper end of the stress plateau region. We found that the first DNA solution (Z=24) only shows transient weakly inhomogeneous shear and steady linear velocity profile. In the more entangled solutions (Z=60 and 156), shear banding is observed in startup rate- and stress-controlled shear in the shear thinning regime. Shear homogeneity eventually returns at the upper end of the stress plateau (shear thinning) regime.
引用
收藏
页码:73 / 83
页数:11
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