Thermo-responsive discotic nematic hydrogels

Abstract

We synthesized a novel thermo-responsive discotic nematic hydrogel. This liquid crystalline polymer nanocomposite was fabricated using extremely high-aspect-ratio (ξ = diameter/thickness ~ 10 3 ) zirconium phosphate (ZrP) nano-sheets embedded into a polymeric network. These nano-sheets were immersed into a solution of constituent monomers of N-isopropylacrylamide (NIPAm) and acrylamide (AAm) with a subsequent polymerization in situ to obtain a hydrogel embedded with the nematic liquid crystal of the 10 nano-sheets. We analyzed the effect of initiator (APS) and catalyst (TEMED) concentration on the nematic domains at ZrP nano-sheet volume fractions (ϕ ZrP ) near the isotropic-nematic (I-N) transition. The mixing during hydrogel preparation allowed the aligning of the nano-sheets into highly ordered domains, which were eventually disturbed by the effect of APS and TEMED on the polymer matrix. The effect of ZrP nano-sheet concentration and temperature on the nematic hydrogels was also studied. By 15 increasing the temperature above the LCST of PNIPAm, the hydrogels entered into a hydrophilic-tohydrophobic transition. Interestingly, hydrogels containing ZrP nano-sheets presented increased hydrogel water retention. In addition, we observed that the variation of the nematic ordering (S 2 ) and ϕ ZrP within the system manipulated the birefringent color patterns of the hydrogels. Finally, a nematic hydrogel placed into a thin-rectangular capillary from 298 K to 333 K presented edge-wrinkling. An isotropic-to-20 nematic transition guided by the increment in the ZrP nano-sheet nematic ordering was observed at a nano-sheet concentration slightly below the isotropic concentration (ϕ I ). 65 emulsions 59 stabilizers, and polymer matrix nanofillers. [60][61][62][63] Extraordinarily, suspensions of highly anisotropic ZrP nanosheets can exhibit liquid crystalline transitions at various aspect ratios (1/ξ << 0.1) and lateral-size polydispersities. 44 Here, we make use of high-aspect-ratio ZrP nano-sheets to 70 obtain thermo-responsive polymer hydrogels of a high nematic

Photo‐Induced Anomalous Deformation of Poly(N‐Isopropylacrylamide) Gel Hybridized with an Inorganic Nanosheet Liquid Crystal Aligned by Electric Field

“…We recently reported the facile synthesis of the cm‐scale anisotropic PNIPA gel by utilizing inorganic nanosheet liquid crystals . Similar anisotropic gels were also reported by several researchers . Inorganic nanosheets are obtained by exfoliation of inorganic‐layered materials such as clays, titanates, perovskites, and niobates .…”

“…[ 7 ] Similar anisotropic gels were also reported by several researchers. [ 8,9 ] Inorganic nanosheets [ 10 ] are obtained by exfoliation of inorganiclayered materials such as clays, [ 11,12 ] titanates, [ 13,14 ] perovskites, [ 15 ] and niobates. [ 16,17 ] The colloids of inorganic nanosheets form LC phases [ 11,14,17,18 ] through their spontaneous orientation induced by excluded volume Poly-( N -isopropylacrylamide) (PNIPA) hydrogel fi lms doped with uniaxially aligned liquid crystalline (LC) nanosheets adsorbed with a dye are synthesized and its anomalous photothermal deformation is demonstrated.…”

Liquid Crystalline Colloidal Mixture of Nanosheets and Rods with Dynamically Variable Length

“…It has been reported so far that the formation of the LC phase of nanosheet colloids can roughly be explained by this theory. 34 , 35 Because both FHT nanosheets and MTs are negatively charged, repulsive force is dominant in the system, so that Onsager theory can be applied in this double-component system. Usually, when treating with Onsager theory, electrostatic repulsion between the charged particles is taken into account, for example, by considering effective size of particles defined as the sum of the size of the particle core and the additional size related to Debye length and charge density.…”

Micellar Lyotropic Nematic Gels

“…Thus, they might find biomedical applications (e.g., artificial tissues) and respond to a broad range of biological and chemical stimuli such as pH-value, salt concentration, solutes, vapor pressure, and temperature, as it was shown for anisotropic hydrogels. [15][16][17][18][19][20][21][22][23][24][25][26] LLC gels are a new approach to anisotropic hydrogels: instead of a water-swollen polymer network, a genuine LLC phase formed by micelles is low-molecular-weight gelators DBS, DBC, and HG1 (see molecular structures in Figure 1). Gels were achieved for all combinations with the exception of the nematic phases of the system H 2 O-n-decanol-CDEAB with the gelator DBC.…”