Manipulating crystal growth and polymorphism by confinement in nanoscale crystallization chambers

Area of Science:

• Materials Science
• Physical Chemistry
• Nanotechnology

Background:

• Classic nucleation theory describes phase stability based on surface and volume free energies.
• Nanoscale confinement significantly alters crystal properties like melting points and enthalpies of fusion.
• Pore dimensions comparable to critical nucleus size can change polymorph stability rankings.

Purpose of the Study:

• To review recent studies on polymorphic and thermotropic properties of crystalline materials in nanoporous matrices.
• To highlight how nanoscopic confinement influences crystallization pathways and outcomes.
• To demonstrate the potential for controlling polymorphism using confined crystallization.

Main Methods:

• Embedding crystalline materials within nanometer-scale pores of porous glass and polymer monoliths.
• Investigating polymorphic and thermotropic properties of embedded nanocrystals.
• Utilizing well-aligned cylindrical pores to determine and manipulate nanocrystal orientation.

Main Results:

• Observed selective formation of amorphous and crystalline phases, including stabilization of metastable phases.
• Demonstrated size-dependent polymorphism and formation of new polymorphs.
• Showcased shifts in thermotropic relationships and measurement of bulk-inaccessible properties.

Conclusions:

• Nanoscopic confinement provides unique insights into crystallization phenomena difficult to achieve otherwise.
• Behaviors under confinement are consistent across various compounds, offering a reliable nanoscale study approach.
• Emerging porous materials will expand explorations of confined crystallization and control over outcomes.