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Preface to the Molecular and Polymer Gels; Materials with Self-Assembled Fibrillar Networks Special Issue This Special Issue of Langmuir is, in some senses, an acknowledgment of the rapid growth that has occurred in the interest in1 and the understanding of gels with fibrillar networks during the last few decades. Because the field has progressed significantly, it is no longer acceptable to use the prescient, yet enigmatic, definition of a gel offered by Dorothy Jordon Lloyd in 1926: “...the colloid condition, the gel, is easier to recognize than to define”;2 nor is Paul Flory’s classification of these gels as “particulate disordered structures” still valid.3 Even as late as 1991, Pierre-Gilles de Gennes did not specifically mention in his Nobel Lecture that gels with fibrillar networks are a part of the great panoply of “soft matter”,4 although clearly they are. At that time, relatively few examples of gels with molecule-based fibrillar networks were known, and fewer had been investigated systematically. In other respects, this issue signals a challenge to the scientific community: our increased knowledge has uncovered a myriad of heretofore unrecognized questions that must be answered before we can truly understand “how” and “why” gels with fibrillar networks form. In part, these questions remain unanswered because the disparate parts of the scientific community who are actively investigating gels with fibrillar networks have not interacted historically. The situation is reminiscent of the centuries-old parable of the blind monks and the elephant. The “monks”; physicists, chemists, biologists, chemical engineers, and theoreticians;have tended to describe gels (i.e., the “elephant”) from their own “perspective”. True progress demands interdisciplinary studies by scientists who, like the blind monks, must be able and willing to listen to their fellow monks. Now, the challenge is to place the pieces of the gel puzzle into a more coherent picture. The individual research articles in this issue make no attempt to do that. Instead, they are intended to demonstrate the exceedingly broad range of systems that form this class of gels, the diversity of scientists who are endeavoring to make new gels with fibrillar networks, and the myriad of approaches to characterize the gels. However, a new type of article, a “Perspective”, has been introduced here. Each Perspective presents a critical (and subjective!) overview of an aspect of the field;a very brief historical introduction to the specific subject and then an assessment of the current status of the area, as well as predictions of future developments and, in some cases, impediments to achieving those developments;while taking cognizance of the other parts of the “elephant”. In part, the field of gels with fibrillar networks has grown enormously in the past two decades because developments in instrumentation have permitted the examination of gel structures and the dynamic processes associated with gel formation and aging in much greater detail than before. Those tools, coupled with more interactions among gel scientists, will drive future advances. It is now recognized that the self-assembly processes involved with gelation are important for many practical reasons in addition to fundamental scientific ones. They have wide-ranging implications in medicine and materials development. Although some of the more applied uses of gels are touched upon in this issue, it is focused more on the fundamental aspects;the state of the art and the most recent systems being explored. Hopefully, it will convince others to enter the field and will help to mold the perception of the “elephant” into a shape that approaches better its multifaceted reality. In preparing this issue, I was aided enormously by the efforts of Jeanne Weiss, my editorial assistant (and boss) and of Dave and Jo Whitten, the Editor-in-Chief and Coordinating Editor of Langmuir. The advice from several scientists, including the authors of the Perspectives, was exceeding useful and is greatly appreciated. Richard G. Weiss Georgetown University (1) A search in the ISI Web of Science using the words, ‘gel’ and ‘fiber’, gave 6 hits for articles published in 1980, 51 for 1990, 384 for 2000, 524 for 2005, and 714 for 2008. (2) Jordon Lloyd, D. Colloid Chemistry; Alexander, J., Ed.; The Chemical Catalog Company: New York, 1926; Vol 1, p 767. (3) Flory, P. J. Faraday Discuss. Chem. Soc. 1974, 57, 7–18. (4) de Gennes, P.-G. Nobel Lecture entitled “Soft Matter”, Dec 9, 1991.
Langmuir 2009, 25(15), 8369–8369
Published on Web 07/28/2009
DOI: 10.1021/la901621x
8369
