“The utility of SAMs is now firmly established and without question as to its impacts on research.”

This paper is a review—a very comprehensive one—of an area of research that has come to have transformational impacts on the field of chemistry over the past two decades. This work began as a collaborative effort in the early to mid-1980s amongst several of us then working at Bell Laboratories together with George Whitesides and his students at Harvard. The focus of the initial efforts was the development of Self-Assembled Monolayers—so-called SAMs—as a model system through which one might study the molecular aspects of organic surfaces and interfaces. This work had many sources of inspiration (mine being the work of people such as Kuhn, Gaines and Zisman, amongst others) but differed in a rather significant way from early work in the area of surface chemistry. The core advance made in this work related to the exploitation of self assembly as a means for engineering (by design) and understanding complex interfacial structures and processes.

Our earliest efforts examined macroscopic phenomena such as wetting and adhesion, using SAMs as a vehicle through which the microscopic underpinnings of such phenomena could be explored and rationalized in molecular terms. This work also required massive involvements with the development of methods of characterization—efforts that in many ways came to set the standards for the approaches followed ever since for work in this area. More importantly though, SAMs—by way of their simplicity and versatility—found extensive applications in diverse areas of chemistry, serving as a broadly enabling platform for studies of electrochemistry, bioanalytical chemistry, molecular electronics, microfabrication, and materials chemistry as specific examples. In establishing the broad utility of assembly as a foundation of nanoscale materials science, SAMs continue to generate broad and evolving interest from workers in diverse fields of interdisciplinary research. The review has great current utility in this regard.

The utility of SAMs is now firmly established and without question as to its impacts on research. Our work, in this sense, has helped shape a very significant set of directions—one of the important lines that contemporary research has followed. The paper of concern here highlights and explores the vast range of the impacts as have developed since a last major review was published in 1992—developing an analysis that illustrates the essential nature of assembly as a foundation for advances in nanoscience. The nature of its reach and impact is demonstrated by the more than 1,000 citations highlighted in the review.

Interfaces are ubiquitous in the world we see around us and reside at the heart of a diverse range of phenomena, ones of both practical and aesthetic interest. In these instances—whether in the context of the shapes formed by drops of water on a leaf or the patterns adopted by cells in tissue—the nature of molecular interactions occurring at an interface play a central and sometimes deterministic role. SAMs allow us to study and exploit such interactions, rendering them amenable to direct experimental manipulation.

It started for me as an idea that sort of half gelled as I was finishing my graduate research at MIT in 1980, just prior to my joining the Technical Staff at Bell Laboratories in Murray Hill, New Jersey. I was examining polymer surfaces and interfaces at that time and the notion of developing a better model for such systems was something that intrigued me. How this might be done in a very powerful way finally became clear with the work performed at Bell and Harvard over the next several years. The initial experiments I performed—simple tests of wetting behaviors of SAMs formed on Au thin films deposited using a very primitive evaporator—showed exceptionally promising macroscopic properties. It was clear that this system—one that would evolve to become the benchmark platform—had something really interesting going on at the most microscopic level. That’s when the big "Now what?" moment hit.

With the instrumentation we had available to us in 1983, how could you ever hope to characterize what that essential, interesting something was at the molecular level—the molecular organizations of the molecules that assemble in the SAM? This was not a trivial challenge and much creative work—empowered by exceptional collaborations—was stimulated to address this deficiency. In some regards, progress in applications always seemed to outpace our abilities to definitively characterize these systems; at least that was the case back in the earliest days of this research.

I believe the most important implications of this sort are ones that speak to the nature of innovation. This was not a project that developed as a result of any sort of programmatic, top-down directed interest (the model followed for much of the work we do these days in research). It was not even a remotely understood (or accepted) interest area for chemistry—the opportunities for progress in the field were understood to lie elsewhere. All the same, this was an idea that several of us were interested in and so, in a completely bootlegged way, came to be a project that we worked on. These collaborations developed naturally and we ultimately were allowed to develop the research to see where it might go. Science is not working this way any more, and that is something that worries me greatly.