Advances in modeling of polymer melt rheology

The development of theories to predict the rheological (i.e., flow) properties of densely packed polymers in the melt or solution state is important because such theories might enable rational design of polymer processing methods for shaping polymers into products, and because they can be used in rheological characterization of polymer molecular weight and long-chain branching. These are important topics, given the enormous volume of polymers produced each year (100's of billions of pounds).The seminal work of de Gennes I and Doi and Edwards-2-4 in the late 1970s established their 'tube model' as the standard theory for predicting polymer rheological properties. The 'tube' idea arises from the notion that entanglements of a long polymer with its neighbors in a dense melt restrict motion of the polymer to a 'tubelike'region - see Figure 1a. Until very recently, the 'entanglements- between densely packed long chains that produce a phenomenological 'tube' constraining the motion of each chain could not be experimentally imaged or simulated, nor could their existence be rigorously derived from microscopic physics, and so acceptance of the tube model has not come without controversy. In addition, most predictions of the tube model in the early years were hardly better than qualitative.