Colloidal particles with complex microstructures via phase separation in swelled polymer microspheres

2017 ◽  
Vol 53 (62) ◽  
pp. 8649-8652 ◽  
Author(s):  
Zhang Luo ◽  
Yitong Li ◽  
Bing Liu
Keyword(s):  
Phase Separation ◽  
Colloidal Particles ◽  
Polymer Microspheres

Incorporating –SO3− groups into PS microspheres results in the synthesis of many kinds of colloidal particles with complex microstructures via phase separation.

Phase equilibria in solutions of rod-like particles

1956 ◽  
Vol 234 (1196) ◽  
pp. 73-89 ◽  
Keyword(s):  
Free Energy ◽  
Phase Separation ◽  
Partition Function ◽  
Colloidal Particles ◽  
Double Layers ◽  
Positive Energy ◽  
Isotropic Phase ◽  
Electric Double Layers ◽  
Rigid Rod ◽  
Anisotropic Phase

A partition function for a system of rigid rod-like particles with partial orientation about an axis is derived through the use of a modified lattice model. In the limit of perfect orientation the partition function reduces to the ideal mixing law ; for complete disorientation it corresponds to the polymer mixing law for rigid chains. A general expression is given for the free energy of mixing as a function of the mole numbers, the axis ratio of the solute particles, and a disorientation parameter. This function passes through a minimum followed by a maximum with increase in the disorientation parameter, provided the latter exceeds a critical value which is 2e for the pure solute and which increases with dilution. Assigning this parameter the value which minimizes the free energy, the chemical potentials display discontinuities a t the concentration a t which the minimum first appears. Separation into an isotropic phase and a some what more concentrated anisotropic phase arises because of the discontinuity, in confirmation of the theories of Onsager and Isihara, which treat only the second virial coefficient. Phase separation thus arises as a consequence of particle asymmetry, unassisted by an energy term . Whereas for a large-particle asymmetry both phases in equilibrium are predicted to be fairly dilute when mixing is athermal, a comparatively small positive energy of interaction causes the concentration in the anisotropic phase to increase sharply, while the concentration in the isotropic phase becomes vanishingly small. The theory offers a statistical mechanical basis for interpreting precipitation of rod-like colloidal particles with the formation of fibrillar structures such as are prominent in the fibrous proteins. The asymmetry of tobacco mosaic virus particles (with or without inclusion of their electric double layers) is insufficient alone to explain the well-known phase separation which occurs from their dilute solutions at very low ionic strengths. Higher-order interaction between electric double layers appears to be a major factor in bringing about dilute phase separation for these and other asymmetric colloidal particles bearing large charges, as was pointed out previously by Oster.

Clustering and phase separation in mixtures of dipolar and active particles

Soft Matter ◽  
2020 ◽  
Vol 16 (15) ◽  
pp. 3779-3791 ◽  
Author(s):  
Ryan C. Maloney ◽  
Guo-Jun Liao ◽  
Sabine H. L. Klapp ◽  
Carol K. Hall
Keyword(s):  
Phase Separation ◽  
Colloidal Particles ◽  
Active Particles

Mixtures of dipolar and active colloidal particles display a variety of states including chains, string-fluids, and motility induced phase separation.

scholarly journals Aspect Ratio Dependence of Isotropic-Nematic Phase Separation of Nanoplates in Gravity

2020 ◽  
Vol 4 (1) ◽  
pp. 17-26
Author(s):  
Abhijeet Shinde ◽  
Xuezhen Wang ◽  
Yi-Hsien Yu ◽  
Zhengdong Cheng
Keyword(s):  
Phase Separation ◽  
Aspect Ratio ◽  
Colloidal Particles ◽  
Formation Rate ◽  
Space Station ◽  
Isotropic Liquid ◽  
Aspect Ratios ◽  
Phase Separation Kinetics ◽  
Gravity Driven ◽  
Time Required

AbstractWe studied isotropic-nematic (I-N) phase separation via gravity sedimentation in suspensions of plate-like colloidal particles of identical thickness but different lateral sizes (diameters). It is well-known that I-N phase transition occurs at a higher concentration for particles with larger aspect ratio (thickness/diameter) than for particles with smaller aspect ratio. Here we report that for the larger aspect ratios of nanoplates, gravity-driven I-N phase separation is faster. In a homogenously mixed I-N biphasic suspension of nanoplates, nematic tactoids nucleate, grow, and then undergo sedimentation in gravity, leading to the formation of a clear horizontal interface between the I and N phase. For I-N coexistent suspension of nanoplates with different aspect ratios but the same amount of nematic fractions, the larger the aspect ratio, the faster the formation of nematic tactoids and interface between isotropic liquid and nematic liquid crystal phase. The tactoid formation rate is governed by the rotational and translational diffusion rates, which are faster at larger aspect ratios. The time required for I-N separation (t*, seconds) varies inversely with the mean aspect ratio (< ξ >) of nanoplates and follows the relation, t* = α < ξ >n, where α = 0.97 ± 1.30 s and n = −2.1 ± 0.2. The phase separation kinetics studied in our experiments offers guidance for the selection of aspect ratio of nanoplates for samples to be studied at the International Space Station (ISS).

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