Polymer International 27 (1 992) 295-296

Pierre-Giiies de Gennes Nobel Laureate in Physics I991

The last Nobel prize awarded in Polymer Science was the Chemistry prize given to Paul J. Flory in 1974, for his studies on the physical chemistry of the high polymers, It is thus very fitting and certainly timely that a prize should be awarded in the area of polymer physics where there has been so much excitement in the last two decades. Professor de Gennes is well known both personally and through his publications to many research workers in laboratories and Universities around the world. We in polymer research naturally claim him (and the reflected glory of the prize of course) as one of us. That there will equally be people working with liquid crystals, and possibly others who work in surface wetting phenomena who make the same claim, is both a measure of the breadth of the Laureate’s interests rand the reason for his award. This breadth enabled some newspapers explaining the award to their readers to say ‘Professor de Gennes invented liquid crystal displays, such as those used in digital watches’ while others claimed ‘he explained how molten polymers flowed in pipes and formed in moulds’. The actual citation of the award committee reads as follows:

For discovering that methods developed for studying order phenomena in simple systems can be generalised to more complex forms of matter, in particular to liquid crystals and polymers.’

Pierre-Gilles de Gennes was born in 1932 in Paris. He became Professor of Solid State Physics at the University of Paris in 1961, Professor at the Collkge de France in 1971 and Director of the Ec8le de Physique et Chemie in 1976. He set up a group to study liquid crystals in Paris in the late 1960s and in 1974 published what has become a standard text, ‘The Physics of Liquid Crystals’ (Clarendon Press). His major contribution in this field was to explain anomalous light scattering from nematic liquid crystals.

Those of us who work in the area of polymer dynamics, and in particular the study of polymer motion by scattering of light or of neutrons, are aware that already, in 1966, he had published two of the basic papers in this area where he calculated the shape of the scattering which would be observed from the internal ‘wriggling’ motion of an isolated polymer molecule. This interest in the motion of one molecule was later extended to take account of the effects of the surrounding polymer molecules in concentrated solutions or melts. In the seventies de Gennes coined the term ‘reptation’ for the move- ment of a molecule relative to its neighbour in entangled melts. The idea that a very long molecule in a tangle with its neighbours will move most easily, and initially, along its own ‘serpentine’ path length, like a reptile, simplified the complexities of the problem so that calculations of the physical consequences of the motion could be made both by himself and by others in the field. For example, the Doi-Edwards model of polymer viscoelasticity which did so much to improve the communication between rheologists and molecular scientists was based on the concept of a polymer molecule moving in a tube or tunnel formed by the surrounding molecules-a development of the reptation hypothesis.

de Gennes and his school of theoreticians have calculated models for the shape and motion of polymer molecules in many situations-in concen- trated solutions and melts; adsorbed onto surfaces; confined in pores; pinned in networks and mem- branes. Asked about the contributions of de Gennes, however, many polymer scientists are likely to quote ‘scaling laws’ or ‘blob theory’ as well as the reptation model already mentioned.

The idea of scaling is to use a characteristic dimension, e.g. molecular size, to ‘scale’ behaviour in different physical situ,ations (temperature, concen- tration). de Gennes’ book, ‘Scaling Concepts in

295 Polymer International(27) ( 1 9 9 2 F - o 1992 SCI. Printed in Great Britain

296 Nobel Luureute in Physics 1991

Polymer Physics’ (Cornell University Press) was published in 1979. In ‘blob‘ theory the relevant length is the screening length-the range of intra- molecular interactions. The polymer chain in a concentrated solution is described in terms of a sequence of blobs, each comprising many monomer units. The size of a blob depends on the screening length which varies with temperature and concen- tration. Within the blob, intramolecular interactions dominate, while outside, on a longer length scale, intermolecular interactions have to be considered. The whole molecule can be considered as a chain of these blobs, and its conformation and dynamics calculated.

By perceiving common features in phenomena in widely differing physical systems, de Gennes has been able to treat many such apparently complex systems and to describe them in general terms. He has opened new fields of physics and stimulated both theoretical and experimental work. In particular his work has had a rather symbiotic relationship with the neutron scattering experiments on polymers which were underway over the period of his theoretical work on these systems. Neutron scatter-

ing allows observation of the structure and motion of individual polymer molecules in crowded sur- roundings, such as concentrated solutions or melts, through the use of deuterium labelling. Hence, it has allowed direct testing of many of de Gennes’ theoretical predictions.

The many scientists who have had the pleasure of discussing experimental results with de Gennes, or of hearing him lecture know that he is excited by and keenly interested in the relationship between pre- diction and experiment. He often perceives his apparently purely scientific concepts in terms of the ultimate exploitation of materials in technical or engineering problems. There is no doubt that he has many more such insights to contribute in future years and all of us who work in polymer research will look forward to future discussions. For the present I am sure we all join our congratulations to the many already received.

Professor Julia S. Higgins Imperial College qf Science, Technology and Medicine, London, U K

POLYMER INTERNATIONAL VOL. 27, NO. 4,1992