Branched polymers and gels

The authors discuss the properties of randomly branched polymers and gels close to the gelation threshold. They discuss the synthesis of such polymers, with special emphasis on an analogy with percolation. They then discuss the influence of polydispersity on the observed power-law behaviours that are observed in the study of their conformation when these materials are swollen upon addition of a good solvent. The effective exponents that are observed are shown to depend strongly on polydispersity. They also discuss the distribution of relaxation times that is present because of this distribution of molecular weights. Experimental results are given at every stage of this discussion for comparison with theory. Although percolation is shown to be an important universality class, they stress that it is by no means the only one.