Editing Polymer (section)

===Transport properties===
[[Transport phenomena|Transport properties]] such as [[mass diffusivity|diffusivity]] describe how rapidly molecules move through the polymer matrix. These are very important in many applications of polymers for films and membranes.

The movement of individual macromolecules occurs by a process called [[reptation]] in which each chain molecule is constrained by entanglements with neighboring chains to move within a virtual tube. The theory of reptation can explain polymer molecule dynamics and [[viscoelasticity]].<ref>{{cite book |last1=Fried |first1=Joel R. |title=Polymer Science & Technology |publisher=Prentice Hall |isbn=0-13-018168-4 |pages=155–6 |edition=2nd|year=2003}}</ref>