Chemomechanics: a bridge across the formidable gap

Lead Research Organisation: University of Liverpool
Department Name: Chemistry

Abstract

The overarching objective of this proposal is to validate experimentally and bring to a new level of utility a conceptual framework for understanding and exploiting the chemical response of polymeric materials to mechanical loads.

The enormous technological importance of polymeric materials is due largely to the remarkable range of their mechanical properties, i.e., their responses to mechanical loads. At the macroscopic scale such loads (stresses) change bulk shapes of objects, but the material response extends across many orders of magnitude in length and time. Almost as soon as the nature of polymers had been recognized certain simple manipulations of polymer solids, melts or solutions were shown to result in fragmentation of polymer backbones without the high temperatures that are normally required for strong covalent bonds to break at detectable rates. The effect is often called mechanochemistry. Mechanochemistry is thought to be important in controlling (1) crack propagation and catastrophic materials failure, (2) stability of surface-anchored polymers in microfluidic diagnostics and high-performance chromatography and (3) behavior of desalination membranes, impact-resistant materials (e.g., bulletproof vests) and tires; and in affecting technological processes as diverse as (4) jet injection (e.g., during inkjet material deposition in organic electronics), (5) polymer melt processing, (6) high-performance lubrication, (7) enhanced oil recovery (e.g., polymer flooding), (8) turbulence drag reduction (e.g., in pipelines, fire fighting, irrigation). Exploiting coupling between localized reactivity and mechanical loads could both advance these technologies and yield fundamentally new materials and processes, including polymer photoactuation (i.e., direct conversion of light into motion to power autonomous nanomechanical devices, control information flow in optical computing, position mirrors or photovoltaic cells in solar capture schemes), efficient capture of waste mechanical energy, materials capable of autonomous reporting of internal stresses and self-healing and tools to study polymer dynamics at sub-nm scales.

To realize this remarkable potential fully the materials science community needs a set of theoretical, computational, synthetic and physicochemical tools and models to guide our effort to identify chemical compositions and molecular structures of monomers and polymer architectures that yield bulk materials with desired stress-responsive characteristics and to enable molecular studies of polymer dynamics particularly at the 5-100 nm lengthscale (the so called "formidable gap"). Achieving this goal requires a general, quantitative understanding of the relationship between the macroscopic parameters that define mechanical loads (e.g., stress or strain tensors) and the molecular properties that govern the changes in chemical reactivity (e.g., energies of activation). EPSRC funding will enable us to develop such understanding with a program that integrates (macro)molecular design and synthesis, physical measurements (using a variety of modern spectroscopic techniques, including single-molecule force spectroscopy and high-resolution X-ray photoelectron spectroscopy), instrument design, quantum-chemical computations, statistical-mechanics and finite-element modeling and theory.

To accomplish this overall objective we will use a series of reactive monomers specifically designed for efficient and accurate kinetic measurements of localized reactivity and molecular interpretation of the results across the whole range of physical systems whose behavior is governed by dynamics of stretched macromolecules. These systems range from individual isolated stretched polymer chains all the way to bulk amorphous polymers under load.

Planned Impact

I suggest that in the short-term (2-4 years) the main beneficiaries will be academic scientists who design, synthesize and study stress-responsive polymers. Over mid-term (4-7 years) broader materials science community will benefit from increased awareness of the diverse chemistry that contributes to the behavior of polymeric materials under loads, a wider adoption of the conceptual framework and experimental tools to study polymer behavior under load that we'll develop and validate, and broad recognition of the opportunities that exploiting coupling between local reactivity and load creates for designing new materials and processes. The most direct societal impact of the proposed program will likely result from it enabling the development of new materials and processes. First such processes and materials may become marketable within ~10 years. Over the next ~15 years the idea of mechanical load as a variable in chemical kinetics could become sufficiently well known to be incorporated in chemical intuition with the potential impact on chemical research similar to that of the broad adoption of the transition state theory by the synthetic community.

A fundamental challenge in the modern materials science is the development of conceptual frameworks, models, and experimental and computational tools to enable engineering bulk materials properties at the molecular level. Our project will contribute to meeting this challenge by developing comprehensive understanding of how localized chemical reactions control the response of polymers to loads. Modern materials are constantly subject to mechanical loads, from production through disposal or recycling, and their response to such loads often determines their technological value. Considerable empirical evidence exists of mechanical loads dramatically altering the kinetic stability of individual covalent bonds making up the material. Such load-induced highly-localized chemistry has been shown, or is thought, to control (1) crack propagation that contributes to catastrophic materials failure, (2) stability of surface-anchored polymers in microfluidic diagnostics and high-performance chromatography and (3) behavior of desalination membranes, impact-resistant materials (e.g., bulletproof vests) and tires; and to affect technological processes as diverse as (4) jet injection (e.g., during inkjet polymer deposition in organic electronics), (5) polymer melt processing, (6) high-performance lubrication, (7) enhanced oil recovery (e.g., polymer flooding), (8) turbulence drag reduction (e.g., in pipelines, fire fighting, irrigation). Exploiting coupling between localized reactivity and mechanical loads could both advance the above technologies and yield fundamentally new materials and processes, including polymer photoactuation (i.e., direct conversion of light into motion, to power autonomous nanomechanical devices, control information flow in optical computing, adjust positions of mirrors or photovoltaic cells in solar capture approaches and refresh electronic Braille displays), efficient capture of waste mechanical energy, materials capable of autonomous reporting of internal stresses and self-healing and tools to study polymer rheology and dynamics at sub-nm scales.

Despite considerable progress made through empirical approaches, these benefits are unlikely to be fully unrealized until our fundamental understanding of coupling between localized reactivity and mechanical loads becomes far more sophisticated. Such coupling occurs across the "formidable gap", the 5 - 100 nm lengthscale, where neither continuum mechanics nor chemical kinetics alone offer adequate description of dynamics and experimental tools to study the dynamics are particularly limited. Whereas much effort has been devoted to scaling this gap from the continuum-mechanics limit, we'll bridge it using chemical tools, positioning chemistry at the center of solving one of the "Grand Challenges" on the 21st century.

Publications

10 25 50
 
Description Our EPSRC-supported work aims at developing the conceptual framework of polymer mechanochemistry, which I defined along with the opportunities it offers, in ChemPhysChem 2017, 18, 1419 and 1422. Our upcoming paper in Nature Reviews Chemistry summarizes the progress made and the outstanding challenges. Our recent publications address major barriers to developing this conceptual framework, including theoretical and experimental elaboration of the factors that determine the diversity of mechanochemical responses (Science, 2017, 357, 299), approaches to exploiting this diversity in practice by integrating multiple productive mechanochemical responses in a single reactive site (Nature Commun., 2017, 8, 147 and Angewandte Chemie 2016, 55, 3040) and strategies of expanding this diversity with molecular mechanochemical feedback loops (Nature Commun. 2016, 7, 13433). We also demonstrated how the methodology developed for mechanochemistry is useful in other fields, including molecular machines (Chem.Comm. 2018, 54, 7991), organometallic catalysis (paper under review in J. Am. Chem. Soc.) and solar thermal energy storage (paper under review in ChemPhotoChem).
Exploitation Route 1. perhaps of greatest significance but also one that will take the longest to be widely adopted are our experimental and modeling methodology to map the distribution of forces along polymer chains is complex loading environments. We have so far demonstrated experimentally the application of this methodology to transient elongational flows generated during sonication and showed computationally that the same principle is likely to work in amorphous materials.
2. The chemistry for multi-modal mechanoresponsive materials is likely to find relevance much faster and may be adopted more broadly than we originally anticipated because it already allows fairly simple (albeit only semi-quantitative unlike 1) estimates of force distribution and relaxation dynamics in amorphous polymers and shows clear application potential.
3. The community is increasingly adopting our approach to quantitative discussions of mechanochemical phenomena based on a series of models we described in 2009-2012
Sectors Aerospace, Defence and Marine,Chemicals,Electronics,Transport

 
Description As a result of the research supported by the EPSRC and published in 2017 three companies reached out to us to discuss collaboration to solve specific problems of industrial importance. WE'll conduct an initial one-year contract research for QinetiQ and are currently in negotiations for contract research for another major UK engineering company (until the contract is finalized, these discussions are covered by a highly restrictive NDA)
First Year Of Impact 2014
Sector Aerospace, Defence and Marine,Chemicals,Manufacturing, including Industrial Biotechology
Impact Types Economic

 
Description Knowledge Exchange
Amount £14,400 (GBP)
Organisation University of Liverpool 
Sector Academic/University
Country United Kingdom
Start 12/2014 
End 03/2015
 
Description Photoactuating polymers of stiff stilbene
Amount $110,000 (USD)
Funding ID 58885-ND7 
Organisation American Chemical Society 
Sector Academic/University
Country Unknown
Start 09/2018 
End 08/2020
 
Description industry/academia partnership
Amount £250,109 (GBP)
Organisation Michelin 
Sector Private
Country France
Start 12/2015 
End 03/2019
 
Description industry/academia partnership
Amount £131,920 (GBP)
Organisation Michelin 
Sector Private
Country France
Start 10/2014 
End 09/2015
 
Description international exchanges
Amount £12,000 (GBP)
Organisation The Royal Society 
Sector Academic/University
Country United Kingdom
Start 11/2014 
End 10/2016
 
Description international exchanges
Amount £12,000 (GBP)
Organisation The Royal Society 
Sector Academic/University
Country United Kingdom
Start 03/2015 
End 02/2017
 
Description newton advanced fellowship
Amount £111,000 (GBP)
Funding ID na140159 
Organisation The Royal Society 
Sector Academic/University
Country United Kingdom
Start 03/2015 
End 02/2019
 
Description Ir-based C-H activation catalysts 
Organisation University of Liverpool
Department Department of Electrical Engineering and Electronics
Country United Kingdom 
Sector Academic/University 
PI Contribution We have performed DFT calculations of the reaction mechanism of Ir-catalyzed C-H bond activation
Collaborator Contribution The partners performed all experiments and catalyst design
Impact none yet
Start Year 2017
 
Description Rh-based O2 reduction catalysis 
Organisation University of Liverpool
Department Department of Chemistry
Country United Kingdom 
Sector Academic/University 
PI Contribution We carried out extensive DFT calculations of the reaction mechanism and assessed several candidate structures to identify the most likely active catalysts. We also advised on kinetic analysis and data modelling
Collaborator Contribution The partner carried out all experimental work (synthesis, kinetic and thermodynamic measurements)
Impact the publication in preparation subject to ongoing evaluation of IP protection
Start Year 2016
 
Description Single-molecule force spectroscopy 
Organisation Duke University
Country United States 
Sector Academic/University 
PI Contribution We have designed and synthesized a series of polymers displaying a new type of mechanochemistry - allosteric (feedback) mechanochemistry. We have also performed high level quantum-mechanical calculations to explain and generalize the results of SMF experiments conducted by the partner
Collaborator Contribution measured single-molecule force behavior of polymers
Impact a paper for Nature Communications has been finalized
Start Year 2015
 
Description THe kinetic theory of single-molecule force spectroscopy 
Organisation Jilin University
Country China 
Sector Academic/University 
PI Contribution We have developed a physical model and associated computer codes to extract thermodynamic information from single-molecule force measurements of reaction rates as a function of applied force
Collaborator Contribution the partners performed the experiments
Impact no outputs yet
Start Year 2016
 
Description foldamer-based materials 
Organisation Case Western Reserve University
Department Department of Chemistry
Country United States 
Sector Academic/University 
PI Contribution designed materials incorporating mechanosensitive moieties and sacrificial bonds
Collaborator Contribution synthesized foldamers
Impact no outcomes yet
Start Year 2015
 
Description mechanochromic materials 
Organisation Xiamen University
Country China 
Sector Academic/University 
PI Contribution we have designed computationally 2 new types of mechanochromic compounds
Collaborator Contribution synthesized the designed molecules and peformed some physicochemical experiments.
Impact a cover article in Angew. Chem. was published (added to publications)
Start Year 2015
 
Description Annual Supramolecular and POlymer Chemistry Lecture, Jilin University and Key Lab of Chinese Academy of Sciences 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I presented an invited lecture on polymer mechanochemistry and its place in the broader field of material science
Year(s) Of Engagement Activity 2017
 
Description EPSRC Career development workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact I participated in the EPSRC-organized workshop for early career researchers
Year(s) Of Engagement Activity 2018
 
Description Free University of Berlin 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Disseminated results of our work to an audience of chemists
Year(s) Of Engagement Activity 2016
 
Description Invited talk at the 2018 Spring American Physical Society meeting 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I gave a broad overview of contemporary polymer mechanochemistry and a tutorial on the conceptual foundations of the field.
Year(s) Of Engagement Activity 2018
 
Description Leibniz Inst. for Interaction Materials/RWTH Aachen U. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I presented an invited lecture on polymer mechanochemistry and its place in the broader field of material science
Year(s) Of Engagement Activity 2018
 
Description MRS Spring meeting 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact we have alerted a group of experts (in materials engineering particularly in aerospace) that would not normally know about research in chemistry about a new framework of thinking about the problems they are interested in based on chemical and physicochemical approaches
Year(s) Of Engagement Activity 2016
 
Description Najing University 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I presented an invited lecture on polymer mechanochemistry and its place in the broader field of material science
Year(s) Of Engagement Activity 2017
 
Description National Chiao Tung U., Taiwan 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I presented an invited lecture on polymer mechanochemistry and its place in the broader field of material science
Year(s) Of Engagement Activity 2014
 
Description National University of Taiwan 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I presented an invited lecture on polymer mechanochemistry and its place in the broader field of material science
Year(s) Of Engagement Activity 2014
 
Description Northwest University, China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact I presented an invited lecture on polymer mechanochemistry and its place in the broader field of material science
Year(s) Of Engagement Activity 2013
 
Description Northwestern Polytechnical University, China 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact I gave a tutorial on polymer mechanochemistry to PhD students in chemistry, physicics, and polymer engineering
Year(s) Of Engagement Activity 2017
 
Description Shhanxi Normal U 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I presented an invited lecture on polymer mechanochemistry and its place in the broader field of material science
Year(s) Of Engagement Activity 2013
 
Description Southwest University, China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact I presented a tutorial on polymer mechanochemistry and its place in the broader field of material science
Year(s) Of Engagement Activity 2013
 
Description Stratingh Institute, U. of Groningen 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Disseminated results of our approach to studying materials behavior
Year(s) Of Engagement Activity 2016
 
Description Sun Yat-Sen University, China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I presented an invited lecture on polymer mechanochemistry and its place in the broader field of material science
Year(s) Of Engagement Activity 2017
 
Description U. of Newcastle 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact A broad overview of contemporary mechanochemistry for PhD engineering students at Newcastle
Year(s) Of Engagement Activity 2016
 
Description Wuhan U./Green Catalyst Int., China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact I presented an invited lecture on polymer mechanochemistry and its place in the broader field of material science
Year(s) Of Engagement Activity 2014
 
Description Xiamen U., China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I presented an invited lecture on polymer mechanochemistry and its place in the broader field of material science
Year(s) Of Engagement Activity 2014
 
Description Zhajian U., China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I presented an invited lecture on polymer mechanochemistry and its place in the broader field of material science
Year(s) Of Engagement Activity 2013
 
Description invited lecture - University of Geneva 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact invited lecture - University of Geneva, Feb. 22, 2019
Year(s) Of Engagement Activity 2019
 
Description invited lecture at Nanyang Technological U. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact invited talk at the ChemE department of NTU, Singapore, June 24, 2019
Year(s) Of Engagement Activity 2019
 
Description invited lecture, MRS - Asia 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact invited talk at a symposium on mechanoactive materials for biological applications at Materials Research Society - Asia
Year(s) Of Engagement Activity 2019
 
Description invited talk: University of Science and Technology of China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I presented an invited lecture on polymer mechanochemistry and its place in the broader field of material science
Year(s) Of Engagement Activity 2017
 
Description plenary lecture 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact plenary lecture at "Building and studying small" symposium, Brussels, 23-25 March, 2019
Year(s) Of Engagement Activity 2019
 
Description plenary lecture at a German Physical Society Spring meeting 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Plenary lecture at a symposium at the spring 2019 meeting of the german physical society
Year(s) Of Engagement Activity 2019
 
Description plenary lecture, 13th Photochemistry Conference, China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I presented a broad overview of the application of photochemical strategies for studying of polymer behavior in complex mechanical loading scenarios
Year(s) Of Engagement Activity 2013
 
Description plenary talk, RAPS 2016 meeting and workshop 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact I gave a talk on starting a career and a new field of science at the same time to the audience of early career scientists from the UK
Year(s) Of Engagement Activity 2016
 
Description visiting professor, THe chemistry research promotion center of Taiwan 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact established collaborative contacts

increased awareness of the field of science among members of the research community of Taiwan
Year(s) Of Engagement Activity 2014