Reversible Polymorphism, Liquid Crystallinity, and Stimuli-Responsive Luminescence in a Bola-amphiphilic π-System: Structure-Property Correlations Through Nanoindentation and DFT Calculations.
We report the design, synthesis, detailed characterization, and analysis of a new multifunctional π-conjugated bola-amphiphilic chromophore: oligo-(p-phenyleneethynylene)dicarboxylic acid with dialkoxyoctadecyl side chains (OPE-C18-1). OPE-C18-1 shows two polymorphs at 123 K (OPE-C18-1') and 373 K (OPE-C18-1″), whose crystal structures were characterized via single crystal X-ray diffraction. OPE-C18-1 also exhibits thermotropic liquid crystalline property revealing a columnar phase. The inherent π-conjugation of OPE-C18-1 imparts luminescence to the system. Photoluminescence measurements on the mesophase also reveal similar luminescence as in the crystalline state. Additionally, OPE-C18-1 shows mechano-hypsochromic luminescence behavior. Density functional theory (DFT)-based calculations unravel the origins behind the simultaneous existence of all these properties. Nanoindentation experiments on the single crystal reveal its mechanical strength and accurately correlate the molecular arrangement with the liquid crystalline and mechanochromic luminescence behavior.
Syamantak
S
Roy
Arpan
A
Hazra
Arkamita
A
Bandyopadhyay
Department of Materials Engineering, Indian Institute of Science , Bangalore 560 012, India.
Devraj
D
Raut
Centre for Nano and Soft Matter Sciences , Jalahalli, Bangalore 560013, India.
P Lakshmi
PL
Madhuri
Centre for Nano and Soft Matter Sciences , Jalahalli, Bangalore 560013, India.
D S Shankar
DSS
Rao
Department of Materials Engineering, Indian Institute of Science , Bangalore 560 012, India.
Upadrasta
U
Ramamurty
Swapan Kumar
SK
Pati
Centre for Nano and Soft Matter Sciences , Jalahalli, Bangalore 560013, India.
S
S
Krishna Prasad
Tapas Kumar
TK
Maji