Search

Human muscles can grow and change their length with body development; therefore, artificial muscles that modulate their morphology according to changing needs are needed. In this paper, we report a strategy to transform an artificial muscle into a new muscle with a different morphology by thermodynamic-twist coupling, and illustrate its structural evolution during actuation. The muscle length can be continuously modulated over a large temperature range, and actuation occurs by continuously changing the temperature. This strategy is applicable to different actuation modes, including tensile elongation, tensile contraction and torsional rotation. This is realized by twist insertion into a fibre to produce torsional stress. Fibre annealing causes partial thermodynamic relaxation of the spiral molecular chains, which serves as internal tethering and inhibits fibre twist release, thus producing a self-supporting artificial muscle that actuates under heating. At a sufficiently high temperature, further relaxation of the spiral molecular chains occurs, resulting in a new muscle with a different length. A structural study provides an understanding of the thermodynamic-twist coupling. This work provides a new design strategy for intelligent materials. [ABSTRACT FROM AUTHOR]

A series of anionic gemini surfactants (GS) were synthesized from the reactant of N, N-dimethylaminoethanol (DMEA) with dicarboxylic acid diester (DADE), after the DADE was synthesized from pyromellitic dianhydride (PMDA) and fatty alcohol. Through rational design, benzene ring was introduced into the molecular structure to work as spacer group; carboxylic acid ammonium salt with hydroxyl as functional hydrophilic head group, and double-alkyl chain performed as hydrophobic tail chains. Then, surface active properties and micellization behavior were investigated respectively. It is found that these novel molecular structure dramatically improved the surface active properties, including critical micelle concentration (CMC: 10−3 mol/L), surface tension (γmin: 26.5 mN/m), conductivity and absorption at interface. Moreover, GS were able to form intermolecular hydrogen bonds, which, together with rigid spacer group, greatly affected the micellization behavior in bulk solution. More importantly, the self-assembly of aggregation with different morphologies can be controlled via adjustment to solution concentration or tail chain length. Finally, GS were applied as soft templates for the shape controllable synthesis of cerium oxide (CeO2) nanoparticles, and CeO2 nanoparticles in diverse shapes were eventually obtained and verified, such as dorayaki shape (double-pancake shape), rod-cluster shape, lamellar shape, butterfly shape and dendrite shape. [ABSTRACT FROM AUTHOR]

A series of carboxylate gemini surfactants (CGS, C n -Φ-C n , n = 12, 14, 16, 18) with diphenyl ketone as a spacer group were prepared using a simple and feasible synthetic method. These CGS exhibited an excellent surface activity with extremely low critical micelle concentration (CMC) value (approximately 10 -5 mol/L), good performance in reducing surface tension (nearly 30 mN/m), and the ability of molecular self-assembly into different aggregate morphologies via adjusting the concentrations, which is attributed to the introduction of diphenyl ketone and carboxylic acid ammonium salt in the molecular structure. Moreover, the surface activity and self-assembly ability of CGS were further optimized by tuning the length of the tail chain. These excellent properties imply that CGS can be a soft template to prepare nanomaterials, especially in morphology-controllable synthesis. By adjusting the concentration of one of CGS (C 12 -Φ-C 12 ), nano-La 2 O 3 particles with diverse morphologies were obtained, including spherical shape, bead-chain shape, rod shape, velvet-antler shape, cedar shape, and bowknot shape. This work offers a vital insight into the rational design of template agents for the development of morphology-controllable nanomaterials.