1 research outputs found
Changing Mechanical Strength in Cr(III)- Metallosupramolecular Polymers with Ligand Groups and Light Irradiation
We
have demonstrated the ability to control the mechanical properties
of metallosupramolecular materials via choice of ligand binding group,
as well as with external light irradiation. These photoresponsive
CrÂ(III)-based materials were prepared from a series of modified hydrogenated
polyÂ(ethylene-<i>co</i>-butylene) polymers linked through
metal–ligand interactions between a CrÂ(III) metal center and
pyridyl ligand termini of the polymers. The introduction of these
CrÂ(III)-pyridine bonds gave rise to new mechanical and optical properties
of the polymer materials. Depending on the type of pyridyl ligand,
density functional theory calculations revealed changes in coordination
to the CrÂ(III), which ultimately led to materials with significantly
different mechanical properties. Electronic excitation of the CrÂ(III)
materials with 450 and 655 nm CW lasers (800 mW/cm<sup>2</sup>) resulted
in generation of excited state photophysical processes which led to
temporary softening of the materials up to 143 kPa (41.5%) in storage
modulus (<i>G</i>′) magnitude. The initial mechanical
strength of the materials was recovered when the light stimulus was
removed, and no change in mechanical properties was observed with
light irradiation where there was no absorbance by the CrÂ(III) moiety.
These materials demonstrate that introduction of metal–ligand
bonding interactions into polymers enables the design and synthesis
of photoresponsive materials with tunable optical-mechanical properties
not seen in traditional polymeric materials