Investigation on the Effect of Photoisomerization-Driven Macromolecular Network Dynamics on the Latency of Photomechanical Actuation
Abstract
Photomechanical machines that rely exclusively on light for power and control offer a new paradigm for mechanical systems that can be operated remotely without onboard power. These machines can enable new DoD capabilities including mechanical systems that are unaffected by electromagnetic interference and dynamic optics capable of self-adjusting to and modulating incident light. Polymeric materials containing light-activated molecular switches are the most attractive platform to realize photomechanical machines, as they can be: 1) synthesized with tunable composition, phase behavior etc., enabling fundamental structure-property relationships to be ascertained, and 2) conveniently processed into nano, micro and macro-scale structures enabling integration into multifunctional device architectures. State-of-the-art materials have not yet lived up to this promise. A breakout in the discovery of next generation of photoactive materials has been held back by the lack of fundamental insights into: 1) How does the population dynamics of photoisomers as a function of the embedded macromolecular network (molecular-level events) control the temporal evolution of the network’s molecular ordering (meso-scale, network segment-level response)? and 2) How does the temporal evolution of molecular ordering relate to the macroscopic, continuum-level photomechanical actuation? Understanding the details of this multi-scale physics of photomechanical response can enable hypothesis-driven materials discovery and a physics-based design of all-opticallypowered/ controlled photomechanical devices. The objective of this collaborative research effort between the University of Pittsburgh and Carnegie Mellon University is to establish experimental and theoretical frameworks for investigating the dynamics of photostrain generation as a function of the topology of the network of photochromic switches. We propose the following tasks to provide a foundation for achieving this objective. i) Synthesize photomechanically active polymeric material platforms, where the network topologies (crosslink density, backbone structure, liquid crystalline order, photoswitch configuration and location) can be systematically varied. ii) Develop a suite of time-resolved characterization platforms to measure the evolution of the photoswitch population, molecular ordering and strain generation as a function of the material composition/structure. iii) Outline the framework for linking chain-scale statistical mechanics to the continuum-scale dynamics of photostrain generation to identify the mechanisms underlying the separation of time-scales as a function of the network structure.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 19, 2018
- Source ID
- N000141812856
Entities
People
- Ravi Shankar Meenakshisundaram
Organizations
- Office of Naval Research
- United States Navy
- University of Pittsburgh