10.1021/ma2001228.s001 Zi Liang Wu Zi Liang Wu Takayuki Kurokawa Takayuki Kurokawa Daisuke Sawada Daisuke Sawada Jian Hu Jian Hu Hidemitsu Furukawa Hidemitsu Furukawa Jian Ping Gong Jian Ping Gong Anisotropic Hydrogel from Complexation-Driven Reorientation of Semirigid Polyanion at Ca<sup>2+</sup> Diffusion Flux Front American Chemical Society 2011 Semirigid Polyanion anisotropic hydrogel gelation process anisotropic gel semirigid polyanion PBDT molecules uniaxial diffusion reorientation PBDT orientation Anisotropic Hydrogel solution reaction cell 2011-05-10 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Anisotropic_Hydrogel_from_Complexation_Driven_Reorientation_of_Semirigid_Polyanion_at_Ca_sup_2_sup_Diffusion_Flux_Front/2654779 We report a macroscopically anisotropic hydrogel developed by the facile dialysis of a synthetic semirigid polyanion in aqueous solution of multivalent cations. By the uniaxial diffusion of Ca<sup>2+</sup> into two ends of a thin rectangular reaction cell containing semirigid polyanion poly(2,2′-disulfonyl-4,4′-benzidine terephthalamide) (PBDT) aqueous solution, centimeter-scale anisotropic hydrogels with the PBDT molecules and their self-assembled fibrous bundles align in <i>perpendicular</i> to the Ca<sup>2+</sup> diffusion direction are obtained. The anisotropic gel shows a higher elastic modulus and tensile fracture stress/strain in the direction parallel to the PBDT orientation than that of perpendicular direction. By observing <i>in situ</i> the gelation process, an extraordinary molecular reorientation of PBDT at the Ca<sup>2+</sup> diffusion flux front is observed for the first time. The mechanism for the molecular reorientation is discussed in terms of complexation and gelation.