Mechanochromic Polyurethane Materials Comprising Triarylmethane Mechanophores
Abstract
Polymers are common materials in our everyday life. At the end of their life cycle or when not able to exert their function, these m,aterials are generally discarded or recycled. However, some polymer materials are used for critical applications such as climbing ro,pes and safety harnesses. Since failure of these systems can lead to serious injury or costly damages, it would be beneficial to hav,e a visual indication of the weakening of the material to avert negative or catastrophic consequences. A convenient way to give an i,ndication of the weakening or microscopic damages of materials it through chemical motifs that respond to mechanical force, so calle,d mechanophores. When incorporated into a polymer material that is subjected to mechanical stress (for example through compression o,r pulling), mechanophores provide a visual readout through the generation of a color. Conveniently, this color change often occurs s,hortly before the failure of the material.The goal of this research projectis to develop a new class of mechanophores based on the t,riarylmethane motif, and exploit the properties of these systems to sense damages in solid polymer materials. The high modularity of, the triarylmethane motif will allow to produce a number of mechanophores that will display colors ranging throughout the whole visi,ble spectrum (i.e. from red to green) under compressive or tensile deformation of the materials. Moreover, this flexibility in molec,ular design should also result in the possibility to control the amount of mechanical stress necessary for the visualization of the,color. Building on the possibility to tune color and mechanical activation of the triarylmethane mechanophores, we propose a researc,h project that consists of three parts. In the first part, we will create mechanophores that lead to different colors and we will te,st such chemical structures in two different polymer materials, namely polyacrylates and polyurethanes. In the second part, we will,create mechanophores that activate at different thresholds of stress and incorporate them into the same polymer materials. In this w,ay, the material will show two different colors depending on the applied mechanical force, for example, a blue color at low force, a,nd a green color at higher forces. Such green color should derive from the sum of blue and yellow, with the yellow color deriving fr,om the activation of a second triarylmethane mechanophopore that requires a much higher force. In this second part, we will focus pa,rticularly on polyurethanes, which are polymers that US Navy uses in rocket motors. Preserving the mechanical integrity of rocket mo,tors is pivotal, since mechanical damages of such systems can have catastrophic consequences such as explosions. Concerning the pres,ervation of the mechanical integrity of rocket motors, in the last part of the project we will work on incorporating the mechanophor,es developed in the first two parts into polyurethane materials that mimic solid rocket motorstypically used by US Navy, and investi,gate their effectiveness as sensors for mechanical damage.To sum up, the research project will generate new fundamental knowledge on, how macroscopic mechanical forces are transferred into materials at the microscopic level, leveraging a completely new mechanorespo,nsive chemical motif. Simultaneously, the materials investigated are highly relevant for strategic navy applications and can be furt,her tailored to suit the needs of US Navy.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 13, 2022
- Source ID
- N629092212036
Entities
People
- Jos Augusto Berrocal
Organizations
- Office of Naval Research
- United States Navy
- University of Fribourg