Shear Banding or Not in Entangled DNA Solutions
Shear Banding or Not in Entangled DNA Solutions
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DOI：
10.1021/ma101267b
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发表时间：
2010-08
期刊：
影响因子：
5.5
通讯作者：
P. Boukany;Shi‐Qing Wang
中科院分区：
文献类型：
--
作者：
P. Boukany;Shi‐Qing Wang
缠结DNA溶液是检验非线性剪切流动行为的理想模型系统。即使当每条链的缠结数Z高于100时，溶液仍然足够柔软，弹性平台模量低于100 Pa，因此可以通过商业旋转流变学进行实验研究，而不会产生歧见和不确定性。我们研究了三种纠缠DNA溶液的在线流动行为，分别为Z=24、60和156，采用粒子跟踪速度PTV和传统流变测量相结合的方法。我们探讨了一些问题，如在中度纠缠解中是否也会出现剪切带，b蠕变是否会导致非线性速度剖面的发展，c在启动剪切和蠕变中产生的剪切带是否在稳态下持续很长时间，以及这些纠缠解是否在应力区上端表现出均匀剪切。我们发现第一个DNA溶液Z=24只表现出短暂的弱不均匀剪切和稳定的线速度剖面。在纠缠度较高的解Z=60和56中，在剪切变薄体系中，在启动速率和应力控制剪切中观察到剪切带。剪切均匀性最终在应力高原剪切变弱的上端恢复。©2009流变学学会。DOI: 10.1122/1.3009299
ntangled DNA solutions are ideal as a model system to examine nonlinear shear flow behavior. ven when the number of entanglements per chain, Z, is higher than 100, the solution is still soft nough with an elastic plateau modulus under 100 Pa and is thus amenable to experimental study y commercial rotational rheometry without ambiguity and uncertainty. We have investigated onlinear flow behavior of three entangled DNA solutions with Z=24, 60, and 156, respectively, sing a combination of particle-tracking velocimetric PTV and conventional rheometric easurements. We explore questions such as a whether shear banding also occurs in moderately ntangled solutions, b whether creep results in development of nonlinear velocity profile, c hether shear banding produced in startup shear and creep persists at long times in steady state, nd d whether these entangled solutions exhibit homogeneous shear at the upper end of the stress lateau region. We found that the first DNA solution Z=24 only shows transient weakly nhomogeneous shear and steady linear velocity profile. In the more entangled solutions Z=60 and 56 , shear banding is observed in startup rateand stress-controlled shear in the shear thinning egime. Shear homogeneity eventually returns at the upper end of the stress plateau shear hinning regime. © 2009 The Society of Rheology. DOI: 10.1122/1.3009299