Editorial pubs.acs.org/cm
Chemistry of Materials’ 1k Club: Understanding the Complexity of Nanocomposites
T
JG: At the time my impression was that this was going to have a significant impact on the flame retardant field because it was one of the few flame retardant approaches for polymers where the flame retardant additive provided an improvement in mechanical properties, instead of a degradation of those properties. In terms of nanocomposites, however, I thought it would just be one of many applications. As it turned out, this property ended up being one of the more important and industrially interesting properties of nanocomposites and led to research exploring flammability properties of other types of nanocomposites, such as those based on carbon nanotubes, for example. Today, if you look at the field of flame retardant research, approximately a quarter of the papers are based upon nanocomposites. CJ: We had envisioned potential large-scale use of polymer− clay nanocomposities for flame retardant materials, to replace brominated chemical flame retardants. These chemicals are now known to have health risks, especially for children. The idea of using a physical barrier or single mineral additive to produce the desired effect, without added chemicals, was really appealing. So far this vision has not been realized, because producing well-dispersed clay in polymers is not simple and has not yet been achieved on a large scale. AM: At the time, the field was headed toward studying nanoparticles in a variety of polymers, to determine if the flame retardant effect was seen in all cases and if the phenomenon could be exploited to generate better fire-safe materials. As for how the area has evolved since then, the research has shown that nanoparticles can provide a good flame retardant effect, when combined with other flame retardant polymers, giving a better balance of properties in the final product. EG: We never imagined the impact these nanocomposites would have on so many research groups (both academic and industrial). When the paper appeared, clay nanocomposites were at their peak; the field has cooled down since, and the emphasis now is more on types of nanoparticles such as carbon nanotubes, graphene, and more recently other types of 2D materials as the reinforcement. Interestingly the “new” nanocomposites share the same challenges facing clay nanocomposites (dispersion, interfacial strength, mechanistic understanding of performance). EM: I was a fresh assistant professor at the time, a dreamer, and an optimist. I thought that nanotechnology and nanocomposites would be the next technological revolution in materials development. To a large extent, this is indeed the reality today, and multiple nanocomposite/nanotechnology breakthroughs have led to new materials with novel functionalities, albeit within application fields that I would not have expected at that time (e.g., fire retardancy, the focus of this paper; multifunctional heat sealants; dielectrics; etc.). Interestingly, many other nanocomposite topics which seemed
his editorial is part of our continuing 1k Club series, in which we interview the authors of papers that have been cited more than 1000 times.1 The goal of the 1k Club series has been to try to discover the roots of the “magic”what was going through the authors’ minds at the time of doing the work and while writing the manuscript? In our latest installment, we spoke with five researchers from the highly collaborative group that co-authored the Chemistry of Materials publication, “Flammability Properties of Polymer−Layered-Silicate Nanocomposites. Polypropylene and Polystyrene Nanocomposites”, from 2000.2 The paper has been cited 1412 times (Google Scholar) and 1086 times (Web of Science/ISI).3 The authors of the paper came from four distinct and geographically separated affiliations, including the National Institute of Standards and Technology (NIST), The Pennsylvania State University (Penn State), Cornell University, and the Air Force Research Laboratory at Edwards Air Force Base. The co-authors we (Chemistry of Materials, CM) spoke with are as follows (Figure 1): Jeffrey W. Gilman (JG, corresponding author) Catheryn L. Jackson (CJ) Alexander B. Morgan (AM) Emmanuel P. Giannelis (EG) Evangelos Manias (EM) CM: At what stage of your academic career were you when submitted this manuscript to Chemistry of Materials? JG: When we submitted this paper to Chemistry of Materials I had been at NIST for several years and had only been working in the nanocomposite field for a few years. Although technically I started working on nanostructured polymers several years earlier at the Air Force Research Laboratory, where we were working on a different class of materials, polyhedral oligomeric silsequioxanes (POSS) polymers. The other co-authors of the paper included my NIST colleagues, Cathy Jackson (currently at Dow Chemical), Alexander Morgan, who was a National Research Council postdoctoral fellow at NIST at the time and is now at the University of Dayton Research Institute, and Richard Harris Jr., who was a senior chemical technician at NIST until his recent retirement. The other co-authors of the paper included Evangelos Manias, who at the time was an assistant professor at Penn State and is now a full professor there, Emmanuel Giannelis, one of the pioneers of layered silicate nanocomposites from Cornell University, and Melanie Wuthenow, who was a student working with Emmanuel at the time. The other co-authors, Dawn Hilton and Shawn Phillips, were working the Air Force Research Laboratory at Edwards Air Force Base. CM: Given the high citation record of this paper, a significant amount of research has been impacted by your findings over the years. Where did you think the field was headed when you wrote the paper? In your opinion, how has this particular research field evolved ever since? © 2015 American Chemical Society
Published: January 27, 2015 401
DOI: 10.1021/acs.chemmater.5b00100 Chem. Mater. 2015, 27, 401−403
Chemistry of Materials
Editorial
CJ: Our paper revealed reduced flammability in polymer− clay nanocomposites through a common char formation mechanism, for multiple systems. It also tied successful char formation back to the precursor morphology and dispersion of clay in the polymer, which explained the mechanism of the flammability reduction. Part of the success was the excellent characterization of the precursor polymer−clay nanocomposites using TEM and XRD, which enabled us to better describe these inhomogeneous materials. I was the principle TEM person and was happy that the cover of the issue chose the TEM image of the nanocomposite (Figure 2). I think the paper
Figure 2. Image from ref 2 featured on the cover of the issue in which the paper appeared.
is an example of a great collaboration with experts from different disciplines and organizations, who cannot always work toward a common goal and bridge gaps in knowledge but were successful in this case. AM: What made the paper special is that it was the first one which really looked at the whole system and why the nanocomposites worked. It showed everyone how to make nanocomposites and how to evaluate them for performance. EG: What makes me satisfied to reread the paper is to see our focus on understanding the relationship between structure/ dynamics/properties. That focus makes the paper still current. EM: The most gratifying aspect of this paper is to see how excellent experimental design and good system selection led to great insights in the fundamentals of very complex multicomponent systems. We combined expertise, we reached across institutional and geographical boundaries, and we employed materials and techniques that were not every co-author’s cup of tea.
Figure 1. Authors from ref 2 interviewed in this 1k Club editorial.
much more promising at that time are now moderate successes or have been largely eclipsed. CM: If you had to put your finger on it, what made your paper special? What are you most happy about when you reread your paper? JG: The satisfying aspect of the work was that it focused on understanding the mechanism. Today the same issues we faced then are still important, such as the importance of nanoparticle dispersion and how to best characterize it. Our current research using fluorescence microscopy to image nanocomposites, 15 years later, is a direct outgrowth of these two issues. 402
DOI: 10.1021/acs.chemmater.5b00100 Chem. Mater. 2015, 27, 401−403
Chemistry of Materials
Editorial
CM: What’s your advice to young scientists trying to discover the next breakthrough in material science? JG: Talk to people, read, and find the big fundamental problems that, if solved, would have a positive impact on society. Clean water, feeding the world, energy efficiency, sustainable energy sources, etc. CJ: I recommend that young scientists aim to solve a problem that has not been tackled, has caused confusion or remains unresolved, or is only partially understood. They should plan a comprehensive study that will produce a body of data to add to the literature in a positive fashion. It is important to carefully read the literature early in the process and incorporate previous work fairly in your manuscript. Finally, they should collaborate with others with the expertise you need to be successful and share in the positive impact this can have in the field. AM: Be open to seeing the potential impact of things and pursue them wherever they may take you, but do good science along the way. If you do something sloppy early on, even if it is a breakthrough, it will tarnish what you did. If, however, you discover something really amazing, and your science is impeccable, people will see it for the fundamental knowledge it is and keep coming back to it to build upon what you did. EG: Remember that most important discoveries are accidental. EM: Look around and tackle problems that interest you the most. Most of the research worth doing, one can no longer do alone; collaborate with the best experts you can get access to. Once you think you discovered something new, make sure you can quantify its details and appreciate its novelty, or triviality.
■
Carlos Toro, Managing Editor Jillian M. Buriak, Editor-in-Chief
AUTHOR INFORMATION
Notes
Views expressed in this editorial are those of the author and not necessarily the views of the ACS.
■
REFERENCES
(1) Earlier 1k Club editorials: (a) Toro, C.; Buriak, J. M. Chem. Mater. 2014, 26, 4669. (b) Toro, C.; Buriak, J. M. Chem. Mater. 2014, 26, 4890. (c) Toro, C.; Buriak, J. M. Chem. Mater. 2014, 26, 5181. (d) Toro, C.; Buriak, J. M. Chem. Mater. 2014, 26, 5819. (e) Toro, C.; Buriak, J. M. Chem. Mater. 2014, 26, 6651. (f) Toro, C.; Buriak, J. M. Chem. Mater. 2015, 27, 1−2. (2) Gilman, J. W.; Jackson, C. L.; Morgan, A. B.; Harris, R.; Manias, E.; Giannelis, E. P.; Wuthenow, M.; Hilton, D.; Philips, S. H. Chem. Mater. 2000, 12, 1866. (3) Citations as of January 7, 2015.
403
DOI: 10.1021/acs.chemmater.5b00100 Chem. Mater. 2015, 27, 401−403
