AI 中文总结
本研究结合流变学与法向力测量，揭示ι-角叉菜胶凝胶的非线性力学由分子连通性及可逆分层结构的形成与破坏调控，发现其存在部分力学可逆性。
AI 中文摘要
角叉菜胶凝胶是热可逆多糖网络，其力学性能源于离子介导的螺旋缔合，但分子组织如何控制非线性变形仍知之甚少。本研究结合线性与非线性振荡流变学及法向力测量，探究KCl溶液中形成的ι-角叉菜胶凝胶的温度依赖性流变行为。ι-角叉菜胶形成均匀且力学可逆的凝胶，其弹性模量随淬冷深度连续增加；深淬冷在屈服前产生明显的应变硬化，与负法向力揭示的内部应力发展相关。值得注意的是，大变形可保持小应变弹性模量，同时逐步抑制应变硬化，证明网络存在部分力学可逆性。本研究用分层网络图像解释这些观测结果：持久的分子间网络控制线性弹性，而更脆弱的介观结构则在变形下实现协同取向与应力放大。研究结果表明，热可逆多糖凝胶的非线性力学不仅受分子连通性调控，还受力学适应性分层结构的可逆形成及最终破坏的调控。
英文摘要
Carrageenan gels are thermoreversible polysaccharide networks whose mechanical properties emerge from ion-mediated helix association, yet how their molecular organization controls nonlinear deformation remains poorly understood. Here, we investigate the temperature-dependent rheology of $ι$-carrageenan gels formed in KCl solutions using linear and nonlinear oscillatory rheology combined with normal-force measurements. $ι$-carrageenan forms homogeneous and mechanically reversible gels whose elastic modulus increases continuously with quench depth. Deep quenches generate pronounced strain stiffening before yielding, associated with the development of internal stresses revealed by negative normal forces. Remarkably, large deformations preserve the small-strain elastic modulus while progressively suppressing strain stiffening, demonstrating a partial mechanical reversibility of the network. We interpret these observations using a hierarchical network picture in which a persistent intermolecular network controls linear elasticity, while a more fragile mesoscale organization enables cooperative alignment and stress amplification under deformation. Our results highlight that nonlinear mechanics of thermoreversible polysaccharide gels are governed not only by molecular connectivity, but also by the reversible formation and eventually destruction of mechanically adaptive hierarchical structures.
