Rams-Baron M, Błażytko A, Matussek M, Lodowski P, Radoń A, Paluch M
August Chełkowski Institute of Physics, University of Silesia in Katowice, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland.
Institute of Chemistry, University of Silesia in Katowice, Szkolna 9, 40-006 Katowice, Poland.
J Phys Chem Lett. 2025 Aug 7;16(31):7953-7959. doi: 10.1021/acs.jpclett.5c01863. Epub 2025 Jul 29.
Many theories attribute the dramatic slowdown in glass-forming liquid dynamics to a transition from independent to cooperative molecular motion. Although the concept of cooperative rearranging regions (CRRs) is well established, the microscopic nature of these regions and their evolution upon cooling remain subjects of active investigation. Molecules with anisotropic shapes offer a new perspective, as molecular reorientations along their long and short axes act as distinct and complementary probes of emerging cooperativity. Here, we introduce model molecules with tailored dipole orientations and demonstrate that the temperature-dependent evolution of a bimodal dielectric response captures the transition from independent to cooperative dynamics. This clear spectroscopic signature marks a significant advance in our understanding of how cooperativity emerges and evolves in glass-forming systems. Upon cooling, CRRs adopt increasingly compact morphologies, leading to a reduction in effective shape anisotropy. This transition from anisotropic to isotropic CRR geometries reveals previously unrecognized mechanisms by which anisotropy becomes suppressed during vitrification.
许多理论将玻璃形成液体动力学的显著减缓归因于从独立分子运动到协同分子运动的转变。尽管协同重排区域（CRR）的概念已得到充分确立，但这些区域的微观本质及其在冷却过程中的演化仍是积极研究的课题。具有各向异性形状的分子提供了一个新视角，因为分子沿其长轴和短轴的重新取向可作为新兴协同性的独特且互补的探针。在此，我们引入具有定制偶极取向的模型分子，并证明双峰介电响应的温度依赖性演化捕捉到了从独立动力学到协同动力学的转变。这种清晰的光谱特征标志着我们在理解协同性如何在玻璃形成系统中出现和演化方面取得了重大进展。冷却时，CRR会采用越来越紧凑的形态，导致有效形状各向异性降低。这种从各向异性CRR几何形状到各向同性CRR几何形状的转变揭示了以前未被认识到的机制，通过这些机制，各向异性在玻璃化过程中被抑制。
