2009 Gerard Fleer

Gerard Fleer (Wageningen)

Gerard J. Fleer was introduced in the field of colloid science by Th. Overbeek himself around 1965. His PhD thesis was completed in 1971 under the guidance of J. Lyklema in Wageningen University. During these years the field of polymer science emerged as a separate discipline. Polymers at interfaces and their effects on colloidal stability have been on the top of Gerards scientific agenda since these days. Throughout his extremely productive scientific carrier he made many seminal contributions (in total about 160 publications, many of these are heavily cited: H-index = 42). We haste to mention however, that we do not nominee Gerard for his productivity, but rather for the leapfrog jumps in progress made by him throughout his carrier. With this award we finally can thank him for being a member of the IACIS board for many years as well as recognize him as a leading person in the polymer physics and colloid science community. 
    Gerard Fleer himself has always been extremely modest about his personal contributions. Time and again he explain(ed)s how lucky he has been to work with so many brilliant people, such as Jan Scheutjens and others. But we should seriously consider the option that Gerard himself makes talent(s) around him flourish fully. Indeed, his personal contributions to the field of polymer science can not be overestimated! A selected survey of Gerards work will suffice to prove this point. 
    Jan Scheutjens started as a graduate student to work with Gerard Fleer after his return from a not-so-successful sabbatical/postdoctoral stay with E. DiMarzio (USA). The target was to introduce so-called excluded-volume effects into a theory for polymers at interfaces, a problem too tricky to solve by DiMarzio himself. Unaware of density functional theory in general, nor familiar with the work of sir. S. Edwards in England (including the close analogy with the Schroedinger equation) and never heard of corresponding work by hard-core physicists such as I.M. Lifshitz A.Y. Grosberg or A.R Khokhlov in Russia, and J. Noolandi in the USA, they invented single handedly the self-consistent field method which now is known as the Scheutjens-Fleer theory. This is indeed remarkable because both Jan Scheutjens as well as Gerard Fleer missed the theoretical physics background that seemed necessary for this! The very first paper published in 1979 now has picked up over a 1000 citations (it is close to the top of the list of all-time highest cited J. Phys. Chem. papers) and numerous extensions in important topics such as self-assembly and wetting, have been constructed on top of it. Key in the success of this work is Gerards ability to explain, also for the non-specialist, the concepts in simple words without compromising the complicated and essential details. Together with a few PhD students he elaborated on experimental systems and found evidence that supported many theoretical predictions, such as adsorption reversibility, the effect of polymer polydispersity, the concept of critical adsorption energy, the adsorption layer thickness, the volume fraction profiles, etcetera. Together with Cohen Stuart, Scheutjens, Cosgrove and Vincent he authored a key reference book, “Polymers at interfaces” in 1994. Being the first author of this book is significant, proving that he indeed was the driving force putting this work together. 
    After the tragic and fatal accident of Jan Scheutjens, Gerard shifted from numerical to analytical investigations of polymers at interfaces. This he did with new élan and found many new dedicated coworkers to collaborate with. Once triggered/challenged, Gerard starts a problem and simply does not give up until all small details are solved. His way of working has been an inspiration to many colleagues and is sometimes compared with “a truck without brakes running down the hill”. He focused on polymer chromatography issues together with Skvortsov and Gorbunov (st Petersburg). He was at the start of polymer brush theory and collaborated with Zhulina, Borisov and Birshtein. The tale of tails finally came to an end in collaboration with Semenov, Joanny and Johner from the French school. The depletion problem was worked on especially with Tuinier, but also with Lekkerkerker, Poon, and others. Why did all these people so eagerly want to collaborate with Gerard? Simply because it pays off! Gerard solved analytically all your problems, admittedly often with an engineering twist to it, rather than remaining restrictive to true first principles. He compares his findings with numerical SCF results, with computer simulations, and of course also extensively with experiments. Finally, being an excellent teacher, he makes sure that everybody can understand the progress made. Possibly the best example of this can be found in a recent lengthy publication in Advances in Colloid Interface Science. He takes 46 journal pages, 71 figures, 4 tables, 153 equations and about 100 references to elaborate on many aspects of polymer depletion and how these influence particular phase diagrams. This paper will be obligatory literature for all scientists in the field for many years to come. 
    In 1996 he received the Langmuir distinguished lecturer award by which the Division of Colloid and Surface Chemistry of the American Chemical Society honored him for his carrier achievements. Knowing the tremendous work produced by hem since then, we are confident that we must follow the ACS and proclaim Gerard Fleer deservingly as our next Overbeek medal laureate.