Polymer
<p >A <b>polymer</b> is a large <a href="http://en.wikipedia.org/wiki/Molecule" title="Molecule" >molecule</a> (<a href="http://en.wikipedia.org/wiki/Macromolecule" title="Macromolecule" >macromolecule</a>) composed of repeating <a href="http://en.wikipedia.org/wiki/Structural_unit" title="Structural unit" >structural units</a>. These sub-units are typically connected by <a href="http://en.wikipedia.org/wiki/Covalent" title="Covalent" class="mw-redirect" >covalent</a> <a href="http://en.wikipedia.org/wiki/Chemical_bond" title="Chemical bond" >chemical bonds</a>.
Although the term <i>polymer</i> is sometimes taken to refer to <a href="http://en.wikipedia.org/wiki/Plastic" title="Plastic" >plastics</a>, it actually encompasses a large class of compounds comprising both natural and synthetic materials with a wide variety of properties.</p>
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Because of the extraordinary range of properties of polymeric materials,<sup id="cite_ref-PC1_1-0" class="reference" ><a href="http://en.wikipedia.org/wiki/Polymer#cite_note-PC1-1" >[2]</a></sup> they play
an essential and ubiquitous role in everyday life.<sup id="cite_ref-MBB1_2-0" class="reference" ><a href="http://en.wikipedia.org/wiki/Polymer#cite_note-MBB1-2" >[3]</a></sup> This role ranges from familiar synthetic <a href="http://en.wikipedia.org/wiki/Plastic" title="Plastic" >plastics</a> and <a href="http://en.wikipedia.org/wiki/Elastomer" title="Elastomer" >elastomers</a> to natural<a href="http://en.wikipedia.org/wiki/Biopolymers" title="Biopolymers" class="mw-redirect" >biopolymers</a> such as <a href="http://en.wikipedia.org/wiki/Nucleic_acid" title="Nucleic acid" >nucleic acids</a> and <a href="http://en.wikipedia.org/wiki/Protein" title="Protein" >proteins</a> that are essential for life.</p>