P. G. de Gennes

Part 1 Liquid crystals - main types and properties: introduction - what is a liquid crystal? the building blocks nematics and cholesterics smectics columnar phases more on long-, quasi-long and short-range order remarkable features of liquid crystals. Part 2 Long- and short-range order in nematics: definition of an order parameter statistical theories of the nematic order phenomonological description of the nematic-isotopic mixtures. Part 3 Static distortion in a nematic single crystal: principles of the continuum theory magnetic field effects electric field effects in an insulating nematic fluctuations in the alignment hydrostatics of nematics. Part 4 Defects and textures in nematics: observations disclination lines point disclinations walls under magnetic fields umbilics surface disclinations. Part 5 Dynamical properties of nematics: the equations of nematodynamics experiments measuring the Leslie co-efficients convective instabilities under electric fields molecular motions. Part 6 Cholesterics: optical properties of an ideal helix agents influencing the pitch dynamical properties textures and defects in cholesterics. Part 7 Smectics: symmetry of the main smectic phases continuum description of smectics A and C remarks on phase and precritical phenomena.

Abstract This new edition of this classic text on condensed matter physics includes the great advances that have taken place since its first publication in 1974. New chapters describe the main types and properties of liquid crystals in terms of the new phases discovered since the middle of the 1970's, and advances in the understanding of local order and the nature of the isotropic to nematic transition. There is an extensive discussion of the symmetry, and macroscopic and dynamic properties of smectics and columnar phases, and their defects, illustrated with numerous descriptions of experimental arrangements. The final chapter is devoted to phase transitions in smectics, including the celebrated analogy between Smectic A and superconductors. Throughout the book there is an emphasis on order-of-magnitude considerations. Its topicality and breadth of coverage will ensure that The Physics of Liquid Crystals remains an indispensable guide for students and researchers alike.

The wetting of solids by liquids is connected to physical chemistry (wettability), to statistical physics (pinning of the contact line, wetting transitions, etc.), to long-range forces (van der Waals, double layers), and to fluid dynamics. The present review represents an attempt towards a unified picture with special emphasis on certain features of "dry spreading": (a) the final state of a spreading droplet need not be a monomolecular film; (b) the spreading drop is surrounded by a precursor film, where most of the available free energy is spent; and (c) polymer melts may slip on the solid and belong to a separate dynamical class, conceptually related to the spreading of superfluids.

We discuss possible motions for one polymer molecule P (of mass M) performing wormlike displacements inside a strongly cross-linked polymeric gel G. The topological requirement that P cannot intersect any of the chains of G is taken into account by a rigorous procedure: The only motions allowed for the chain are associated with the displacement of certain “defects” along the chain. The main conclusions derived from this model are the following: (a) There are two characteristic times for the chain motion: One of them (Td) is the equilibration time for the defect concentration, and is proportional to M2. The other time (Tr) is the time required for complete renewal of the chain conformation, and is proportional to M3. (b) The over-all mobility and diffusion coefficients of the chain P are proportional to M−2. (c) At times t < Tr the mean square displacement of one monomer of P increases only like 〈(rt − r0)2〉 = const t1/4. These results may also turn out to be useful for the (more difficult) problem of entanglement effects in unlinked molten polymers.