Solution chemistry solvent-polymer interactions

So far in this book, we have focused on aspects of polymer synthetic chemistry and what can be considered local structure, the arrangements of units in a chain and how these can be characterized spectroscopically. In the next few chapters our focus shifts to a more global scale and involves the physics and physical chemistry of polymer materials. We will start with the shapes or conformations available to chains in solution and the solid state, how these chains interact with one another and other molecules (e.g., solvents), and the- conditions under which chains can organize and aggregate into larger scale structures, as in crystallization (or, more briefly, some of the fascinating morphologies formed by block copolymers). 

As in the case of aqueous solutions of electrolytes, computer studies have shed much light on the behaviour of aqueous solutions of non-polar and apolar molecules. They can give information on solute-solvent and solvent-solvent interactions in such solutions. This is a powerful tool for studying hydrophobic phenomena and is limited only by the accuracy of the assumed model and the quantities relevant to this model which are fed into the computer simulations. Simulation is of particular importance in the solution chemistry of large macromolecules and polymers which are extremely difficult to study experimentally, especially in dilute solutions. They are likely to be a dominant feature of the future study of hydrophobic hydration. 

More generally, polymers in solution can experience three types of solvent conditions, with theta solvent condition being intermediate between good and bad solvent conditions. The solvent quality depends mainly on the specific chemistry determining the interaction between the solvent molecules and monomers. It also can be changed by varying the temperature. 

Theta solvent n. A solvent, at a particular temperature, in which the polymer is at the edge of solubility and exists in the form of a statistical coil. Long-range forces between polymer molecular segments are balanced by polymer solvent interactions. At these conditions the second virial coefficient becomes zero and entropy is at its minimum. Kamide K, Dobashi T (2000) Physical chemistry of polymer solutions. Elsevier, New York. Flory PJ (1969) Statistical mechanics of chain molecules. Interscience Publishers Inc., New York. Flory PJ (1953) Principles of polymer science. The Cornell University Press, Ithaca, NY. 

The physical chemistry of ionic solutions deals with ions and solvents and how ions interact dynamically with water as they move about in solutions. The study of ion-ion interactions tells us how ions associate, sometimes even forming polymers in solution. These interactions are important for the new spectroscopic techniques, neutron diffraction and infrared spectroscopy and for molecular dynamics (MD). 

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