Magnetic-field alignment of micellar lyotropic nematic gels and their memory-effect
Abstract
Many potential applications of anisotropic hydrogels, such as media for tissue engineering and drug delivery, as well as biomimetic actuators, require gels that are macroscopically aligned over macroscopic length scales. Micellar lyotropic nematic gels, a relatively new class of anisotropic hydrogels, may provide a rather simple and robust approach to macroscopically aligned anisotropic hydrogels if the long-range orientational order of the surfactant-based lyotropic liquid crystal is transferred to the order of the gel network. Here, we report a kinetically controlled process by which we have successfully fabricated centimeter-long sample films of macroscopically aligned nematic gels. This was achieved by growing a self-assembling fibrillar network (SAFIN) of the gelator 3,5 bis (5-hexylcarbamoyl-pentoxy)-benzoate acid hexyl ester (BHPB-6) in a magnetically aligned lyotropic nematic liquid crystal of rod-like micelles formed by the surfactant N,N-dimethyl-N-ethyl-1-hexadecylammonium bromide (CDEAB). Once the gel network is fully formed after typically 10 hours, the macroscopic alignment of the sample is (i) preserved also after removal of the magnetic field and (ii) even recovered after melting and re-forming the nematic liquid crystal. The fibrillar network thus appears to have a remarkable memory-effect that stabilizes the anisotropy of the gel and results in very robust anisotropic hydrogels.
- This article is part of the themed collection: Honorary collection in memory of Professor Dr Helmut Ringsdorf