| Themes > Science > Chemistry > Organic Chemistry > Organic Chemistry Index > Polymers > Polymer Crosslinking |
A polymer's properties can be carefully tailored to the desired use by a number of methods. One of these is crosslinking: creating bonds between different polymer molecules. For example, polyisoprene (natural rubber) is a long, unbranched molecule. The material is help together by London dispersion forces and acts much like a molecular solid: flexible, low strength, low melting point. Addition of a small amount sulfur to the polyisoprene creates a series of S-S disulfide bridges between the polymer chains: this is the process known as vulcanization. As more and more chains are linked this way, the material becomes much harder and heat resistant. Large amounts of sulfur result in a very hard, brittle material ebonite that acts more like a network covalent material. |
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