Jean-Pierre Cotton passed away on January 20, 2016, at the age of 74. He was a leading figure in soft matter studies by Small Angle Neutron Scattering (SANS). As we will see below, he took advantage of two opportunities, one technical and one scientific. In 1969, after graduation from SUPELEC engineering school, he was appointed by the CEA-Saclay in the Service de Physique des Solides et de Résonance Magnétique. He joined the inelastic scattering group and participated to studies of critical scattering by magnetic samples, using a new experimental set-up on a cold neutron guide issued from the EL3 reactor. Concomitantly, after attending de Gennes' lectures on the physics of polymers at Orsay University, Gérard Jannink proposed to use this new equipment for the study of the conformation of polymers in solution. After preliminary experiments, Jean-Pierre Cotton realized that progress could only be possible with the design of an advanced scattering instrument. For this purpose, he designed in 1973 at Saclay an area ring-shaped detector for the first SANS instrument.
He was leader in the founding of a Collaborating Research Group (CRG) called STRASACOL linking the Saclay group (Jannink, Daoud, Cotton and Farnoux) with the researchers of the Centre de Recherche sur les Macromolécules in Strasbourg (Prof. Henri Benoit) and the Collège de France (Prof. Pierre-Gilles de Gennes). The unique experimental environment and the scientific knowledge of this CRG allowed to fully use the new experimental set up of the ILL at Grenoble. This led in the '70s to a series of original results on the conformation of polymers in solution (his thesis in 1973), bulk polymers in amorphous state, polyelectrolytes, copolymers.… In these experiments, Jean-Pierre Cotton always used the same method: first identification of the scientific problem, then search for an adequate system to be studied by SANS, finally measurement of a relevant parameter leading to answer the question. This method linked with a hard work has been rewarded in 1977 by the Groupe Français d'études et d'applications des Polymères prize and by the CEA prize in 1986 with the Saclay group.
In 1974, with the creation of the Laboratoire Léon Brillouin (LLB) and the opening of the neutrons scattering instruments to external users, Jean-Pierre Cotton gave at Saclay a series of lectures on the “Introduction to neutron spectrometry”. He was the editor of these lectures and also wrote the bases of the contrast notion in SANS. These reference books were used by all the newcomers in SANS until the end of the '90s. In 1980, he started a theoretical study on star shaped polymers, known as the Daoud-Cotton model. Then, in collaboration with a team in the College de France, he showed experimentally the existence of bi-continuous phases in amphiphilic solutions.
In 1984, Jean-Pierre Cotton entered a new research field on liquid crystal polymers (LCP) and studied by SANS the conformation of comb-like LCPs in bulk state, in the nematic and smectic phases. Their dynamics were also studied by measuring the deformation and relaxation of polymer conformation by SANS. He then initiated a study to check the theoretical de Gennes' prediction on linear LCP conformation and demonstrated the existence of hairpin folding. During this period, he established a strong collaboration with the Centre de Recherche Paul Pascal in Bordeaux to study many architectures.
From the beginning of '80s to the end of '90s, he was in charge of the SANS group at LLB. He was then the leading force with novel and creative ideas for the design and improvement of the experimental set-up for the new ORPHEE reactor. He helped his young colleagues for their research program, letting them free to develop their own ideas. His working method was a model during all these years. He gave lectures on contrast variation, developed the zero average contrast method that were published in two review articles (1996 and 1999). He proposed a time of flight method that provides the advantages of a pulsed source to a reactor, a method now applied to reflectometry, and established a method of absolute measurement from the determination of the incident flux. In addition to the lectures on SANS applied to polymer studies, he gave lectures on colloids and porous media, and on technical methods for the study of interfaces. In 1990, he initiated the publication of the first spring school proceedings of the Société Française de la Neutronique. These were followed by many others.
With his method and a deep knowledge of the soft-matter field, 120 papers and 8 reviews, he had a strong contribution to the education of the French soft matter community in the use of SANS. He retired in 2004, and was honored by a scientific day. All his colleagues are deeply sorrowed by his sudden passing away. He will be remembered for his scientific results, and also as a nice man with a solid sense of humor.