Achieving Self-Healing via Hydrogen Bonded Co-crystallization in Molecular Crystal

Jaykishan, Odhavia Sahil (2025) Achieving Self-Healing via Hydrogen Bonded Co-crystallization in Molecular Crystal. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Odhavia Sahil Jaykishan (20MS100)) 20MS100_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (2MB)

Abstract

Molecular crystals exhibit a broad range of mechanical behaviours such as elastic, plastic, brittle, or even self-healing, driven by their intermolecular forces and anisotropic lattice structures. In pharmaceutical APIs, Young’s moduli typically span 0.5–15 GPa, balancing resistance to deformation with sufficient plasticity for robust tablet formation. Excessive stiffness hampers powder compaction and yields friable tablets, whereas overly plastic crystals stick to punches or fracture during milling. Co-crystallisation has emerged as a powerful strategy to tune mechanical properties via targeted modulation of hydrogen-bond networks. Isoniazid (INH), a first-line antitubercular API, forms stiff, brittle needles (≈ 18 GPa) owing to its three-dimensional hydrazide–hydrazide and hydrazide–pyridine synthon network. Herein, we report the synthesis and characterisation of INH:IPA co-crystals in the polar Pmn2₁ space group, achieved by mechanochemical grinding of INH with isophthalic acid (IPA) in a 2 : 1 ratio followed by slow methanol evaporation. Under mechanical stress, these co-crystals demonstrate rapid self-healing as captured by high-speed optical microscopy and SEM fully restoring their integrity within ~15 ms.

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