Mesophase-induced Vitrification in Coordination Polymers via Aliphatic Chain Dynamics

Hybrid glasses derived from coordination polymers (CPs) promise a fusion of processability and structural functionality, yet their formation is fundamentally limited by poor thermal stability and high melting points. Here, we demonstrate a mesophase-mediated vitrification mechanism in a series of magnesium-based CPs (MgC _n DC, n = 2–7) featuring aliphatic dicarboxylate linkers. Upon thermal desolvation, these frameworks transition into a mesomorphic state that retains coordination integrity while inducing conformational disorder in the organic substructure. This intermediate state enables a direct glass transition without requiring full melting. The resulting glasses exhibit distinct calorimetric transitions and tunable mechanical properties governed by chain length and topology. Furthermore, only the longest-chain member ( n = 7) is also capable of conventional melting after forming the mesophase, leading to a melt-quenched glass with lower mechanical stiffness due to partial disruption of its metal-organic backbone. Spectroscopic and structural analyses reveal that mesophase vitrification proceeds via unlocking rotational freedom in the hydrocarbon chains, drawing strong parallels to semicrystalline polymer behaviour. These findings establish a design strategy for vitrifiable coordination networks by integrating principles from polymer dynamics and mesomorphism.