One-Pot Thermo-Remendable Shape Memory Polyurethanes
- Publication date
- 2014
- Publisher
Abstract
Furan-based thermoset polyurethanes
have been prepared in a one-pot
fashion with the ability to self-mend under mild temperature conditions,
by making use of a Diels–Alder shape-memory assisted self-healing
(DASMASH) approach. For this, thermoreversible covalent bonds, obtained
by Diels–Alder chemistry, are introduced as cross-linkers into
a polycaprolactone (PCL) containing polyurethane material. It is demonstrated
that, after introduction of a crack into the PU-thermoset, Diels–Alder
bonds preferentially break, regenerating free furan/maleimide functional
groups, while the shape memory effect favors the crack closure at
temperatures above the melting point of PCL, simultaneously resulting
in a reformation of the reversible cross-links. The reversibility
and shape memory ability of the materials were optimized and studied
by FTIR, <sup>1</sup>H NMR and tensile measurements. Different compositions
were used to properly understand the role and influence of each component.
The polyurethane materials healed at 50 °C after mechanical damage
induced by either the application of a large tensile deformation or
by performing controlled macro/micro scratches with a depth sensing
indenter. Online FT-IR monitoring provided a kinetic description of
the system reversibility for numerous cycles. Furthermore, mechanical
recovery with complete disappearance of the microscratches was accomplished
after multiple cycles of large tensile deformation. The results were
not only confirmed by an optical inspection and scanning electron
microscopy, but also with confocal microscopic mapping, by comparison
of the cross-section profiles of the microscratches before and after
healing