Polymer-confinement-induced nematic transition of microemulsion droplets

¹ Department of Physics, Ochanomizu University 2-1-1, Otsuka, Bunkyo-ku, Tokyo, 112-8610, Japan
² Department of Chemistry, Tokyo Metropolitan University 1-1 Minami-Osawa, Hachioji-shi, Tokyo, 192-0397, Japan
³ Department of Physics, Tohoku University Aoba, Aoba-ku, Sendai, 980-8578, Japan
⁴ Department of Physics, Yamaguchi University 1667-1 Yoshida, Yamaguchi-shi, Yamaguchi, 753-8512, Japan

Received: 19 April 2005
Accepted: 1 June 2005

Abstract

We study a shape change of spherical microemulsion droplets when water-soluble polymers are confined inside of them. Upon confinement, spherical droplets deform to prolate ellipsoid droplets while keeping the total surface area and the total enclosed volume of all the droplets constant. We found that an increase of the degree of polymer confinement causes an increase in the uniaxial anisotropy of the prolate droplet, which leads to an isotropic-nematic transition in the concentrated droplet region. As a possible origin of this structural transition, we consider a loss of the conformational entropy of polymer chains due to the confinement.