w:decsdecs97 formdec.doc Tanaka 9616791 This experimental and theoretical project is devoted to study of the phases and phase transitions of various disordered polymers and heteropolymer gels. Disorder in this context includes disorder of sequences (when several monomer species are polymerized together, with the sequence of monomers bearing some useful information), disorder of branches, and topological disorder that is related to knots, links, and entanglements. In experiment, it is intended to explore the phases and phase transitions of various disordered polymers as controlled by both parameters such as temperature, choice of solvent, etc, and also by the preparation conditions, which control the degree of disorder. It is intended also to examine from the point of view of design: (i) other types of disordered polymers, including branched polymers, knots, and ; (ii) realistic degrees of compactness, when density fluctuations are coupled to freezing and to design, providing for flower- or micelle-type structures; (iii) realistic types of interactions, including long-range Coulomb interactions; and (iv) states of partial equilibrium, important for folding kinetics. In work on gels, the first goal is to observe the freezing phase transition in a polymer gel. A second goal in this area is to experimentally realize the idea of sequence design, to allow the production of gels capable of freezing into a state which exhibits at least certain elements of the desired conformation. This combined theoretical and experimental study will shed light on basic physical principles behind phase transitions of disordered polymers and gels, and will be of great potential importance for the physics of these fascinating materials, as well as for their applications in biology, medicine, and technology. %%% This experimental and theor etical project is devoted to study of a class of materials known as polymers, which are extremely long molecules composed of repeating chemical units. The questions of interest relate to the degree of randomness or disorder in masses of such material, and the conditions under which such material, originally in a liquid state, can freeze and become rigid. Polymers in some cases can be thought of as long flexible molecular strings, which, when dissolved in a liquid solvent, resemble cooked spaghetti in water. This work will include many other types of polymers, including those in which branches occur, for example. One of the central questions in this work is to clarify the conditions, for example, temperature, the type of solvent, and the type of polymer molecules, which lead to a transition from a liquid to a rigid solid. A somewhat similar, but irreversible, freezing transition for example occurs when epoxy glue hardens, but the phenomenon is to be examined in this project in a very fundamental and broad manner, leading to results which will be of predictive value for a wide range of polymers and conditions. The utility of the results of this work may include situations in biology and medicine, as well as in technology. ***
