Spontaneous sense inversion in helical mesophases
Spontaneous sense inversion in helical mesophases
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DOI：
10.1209/0295-5075/107/36001
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发表时间：
2014-05
期刊：
影响因子：
--
通讯作者：
H. H. Wensink-H.
中科院分区：
文献类型：
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作者：
H. H. Wensink-H.
我们研究了螺旋斑片状圆柱体作为手性（生物）聚合物和螺旋形胶体棒的通用模型的手性双折射相的螺距敏感性。宏观螺距的行为进行了研究，从微观原则，通过调用一个简单的密度泛函理论广义，以适应弱扭曲的导演领域。当改变沿沿着局部螺旋指向矢的取向度时，我们发现手性双螺旋相位表现出突然的方向反转，由此螺旋对称性从左手变为右手，反之亦然。由于局部对齐是由热力学变量，如密度，温度或外部定向场的振幅，这样的螺距方向反转可以预期在系统的螺旋介晶的热致和溶致起源。我们表明，螺旋对称性的自发变化是一个直接的后果，具有一定规定的内部螺旋粒子之间的对抗有效扭矩。这些结果可能有助于开辟新的途径，通过明智地选择外部控制参数来精确控制手性组装体的螺旋手性。
We investigate the pitch sensitivity of chiral nematic phases of helicoidal patchy cylinders as a generic model for chiral (bio-)polymers and helix-shaped colloidal rods. The behaviour of the macroscopic helical pitch is studied from microscopic principles by invoking a simple density functional theory generalised to accommodate weakly twisted director fields. Upon changing the degree of alignment along the local helicoidal director we find that chiral nematic phases exhibit a sudden sense inversion whereby the helical symmetry changes from left- to right-handed and vice versa. Since the local alignment is governed by thermodynamic variables such as density, temperature or the amplitude of an external directional field, such pitch sense inversions can be expected in systems of helical mesogens of both thermotropic and lyotropic origin. We show that the spontaneous change of helical symmetry is a direct consequence of an antagonistic effective torque between helical particles with a certain prescribed internal helicity. The results may help opening up new routes towards precise control of the helical handedness of chiral assemblies by a judicious choice of external control parameters.