Bullvalene-Containing Molecular Glasses.

Area of Science:

• Materials Science
• Organic Chemistry
• Physical Chemistry

Background:

• Organic molecular glasses are crucial for pharmaceuticals and electronics due to their processability and compatibility.
• A limited number of functional groups effectively promote glass formation over crystallization.
• Investigating novel molecular structures is essential for developing advanced amorphous materials.

Purpose of the Study:

• To explore the potential of shapeshifting heterodisubstituted bullvalenes (BVs) as building blocks for organic molecular glasses.
• To understand how the dynamic isomerism of BVs influences glass formation and material properties.
• To compare the characteristics of BV-containing glasses with those of fixed-constitution analogues.

Main Methods:

• Synthesized novel molecular structures incorporating the bullvalene (BV) unit into liquid crystal mesogen frameworks.
• Utilized differential scanning calorimetry (DSC) to analyze thermal properties, including glass transition temperatures.
• Employed polarized optical microscopy (POM) to observe material behavior and phase transitions.

Main Results:

• Incorporation of the constitutionally dynamic BV unit successfully induced glass formation in liquid crystal mesogens.
• BV-containing molecular glasses exhibited distinct thermal expansion coefficients compared to fixed-structure glasses, evidenced by low-temperature fracture.
• The shapeshifting nature of BVs demonstrably influenced macroscopic physical properties.

Conclusions:

• Shapeshifting building blocks, like bullvalenes, are effective in promoting the formation of organic molecular glasses.
• The dynamic isomerism of BV units can be leveraged to tune the physical properties of amorphous materials.
• This research opens new avenues for designing functional organic glasses with tailored characteristics for various applications.