Mechanical properties of Organic crystals: from polymorphism to autonomous actuation

Chakraborty, Priyam (2025) Mechanical properties of Organic crystals: from polymorphism to autonomous actuation. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Priyam Chakraborty (20MS153)) 20MS153_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (4MB)

Abstract

Crystal engineering has advanced organic functional crystals, focusing on both reversible and irreversible molecular deformations with promising applications. The discovery of self-healing molecular crystals capable of millisecond-scale actuation has garnered significant interest, offering great potential to enhance the practicality of self-sustaining molecular materials. Moreover, crystal engineering in pharmaceutical solids enables optimization of tabletability, with mechanical property analysis supporting compaction studies and facilitating polymorph control. Although, despite numerous studies on pharmaceutical solids, a comprehensive framework for analysing the mechanical and polymorphic properties of a specific API has yet to be established. Therefore, in the first part of my work, I will focus on a pharmaceutical solid that exhibits unique two-dimensional exfoliation and irreversible plastic bending under mechanical stress. The applied stress induces local mechanostimulated polymorphic transformations within the crystals, as demonstrated by localized micro-Raman studies. This investigation aims to establish the aforesaid framework for analysing the mechanical and polymorphic properties of APIs, facilitating improved control over tabletability and polymorph behaviour. In the latter part of my work, I will explore simple salt systems composed of substituted amines and carboxylic acids. Upon crystallization, these systems exhibit autonomous actuation behaviour following crystal fracture. Overall, this work establishes a framework for analysing API mechanical and polymorphic properties. Additionally, it explores autonomous actuation in salt systems, advancing functional material design.

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