Multifunctional Charge Transfer-Based Supramolecular Materials with Tunable Thermochromism
Tianyu (Kelvin) Yuan1, Lei Fang 1,3 and Mark A. Olson 2
1. Materials Science and Engineering Department, Texas A&M University, 3003 TAMU, College Station, TX, USA
2. School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
3. Department of Chemistry Texas A&M University, 3255 TAMU, College Station, TX, USA
Stimuli-responsive materials, such as thermochromics, have found mass usage and profitability in manufacturing and process control. Imparting charge transfer-based functional supramolecular materials with tunable thermochromism, emerges as an ideal strategy to construct optically responsive multifunctional assemblies. A new series of thermochromic charge transfer-based supramolecular materials assembled in water has been developed. These assemblies are composed of a bis-bipyridinium-derived acceptor and a series of commercially available donors – namely, the neurotransmitter melatonin and its analogue bioisosteres. By tailoring the chemical structure of the donors, the strength of the charge transfer interactions can be tuned. Thermochromic aerogels and inks of these materials are prepared, with a large selection of colors, in environment-friendly solvents and demonstrate tunable thermochromic transition temperatures ranging from 45 to 105 oC. Stamped and inkjet-printed thermochromic patterns can be prepared from their aqueous solutions which also showed favorable compatibility with commercial inks. Mechanistic studies reveal that the two types of water molecules were bound to the supramolecular complexes with different strength, and the more weakly bound water is responsible for the thermochromic transitions.
Overall, this work presents a novel series of donor-acceptor CT-based supramolecular materials which feature versatile processability and tunable thermochromic properties. The unfolded design principles and underlining mechanism in this work provide essential insights for the future development of reversible and recyclable thermochromic supramolecular materials.
Keywords: Thermochromic, tunable, donor-acceptor charge-transfer, supramolecular materials, inkjet printing.