Anisotropic Hydrogel from Complexation-Driven Reorientation of Semirigid Polyanion at Ca2+ Diffusion Flux Front
journal contributionposted on 10.05.2011 by Zi Liang Wu, Takayuki Kurokawa, Daisuke Sawada, Jian Hu, Hidemitsu Furukawa, Jian Ping Gong
Any type of content formally published in an academic journal, usually following a peer-review process.
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 Ca2+ 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 perpendicular to the Ca2+ 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 in situ the gelation process, an extraordinary molecular reorientation of PBDT at the Ca2+ diffusion flux front is observed for the first time. The mechanism for the molecular reorientation is discussed in terms of complexation and gelation.