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Elastomer in equilibrium with forces and solvent
A long polymer consists of many monomers. The monomers are covalently bonded, and two bonded monomers may rotate relative to each other. Consequently, the polymer may be modeled as a chain of many links, each link representing a monomer. At a finite temperature, the polymer rapidly changes from one configuration to another.
A large number of long, flexible polymers can be crosslinked by covalent bonds to form a three-dimensional network. Subject to forces, the network undergoes large elastic deformation. The network is commonly called an elastomer.
Now immerse the network in an aqueous environment, such as pure liquid water, a moist gas, and aqueous solutions. If the polymers of the network are hydrophilic, the network may imbibe a large quantity of water, and swell greatly. The network and water molecules form an aggregate known as a hydrogel.
The time-dependent process of water migrating in the network is considered in notes on poroelasticity. We now focus on the conditions of equilibrium of the network, the forces, and the aqueous environment.
Materials added in teaching the course in Spring 2013: