 This shows an example of one chain of a polymer molecule. I've done this one for PVDF, where we have fluorine atoms shown in yellow, carbon atoms shown in black, and hydrogen atoms shown in white. This configuration is the zigzag chain, sometimes called the straight chain. And it's called the straight chain because if you put it on end and you look at it exactly at the right orientation, the carbon atoms will make a straight line. It is apparent that it is possible to twist these chains so that instead of having a perfect regular arrangement of atoms, I have local arrangements so the individual atomic coordination hasn't changed, the bond lengths haven't changed, the bond angles have not changed much, but the overall translational symmetry has been completely lost as we go from the straight chain to one of these twisted or coiled chains. It will also be apparent that the way in which this coils is going to depend on how large the side groups are. So if instead of having something relatively modest in size, like a fluorine, I were to put a large benzene ring here, that large benzene ring would limit how close I could make this part of the chain coil up with respect to that. We call those interactions steric effects, and the steric effects will control the overall chain confirmation rules for polymeric materials.