Glass transition dependence upon polymer structure

There are a number of transitions, depending upon the complexity of the molecular structure, for example the temperature at which rotation stops for a styrene unit about its axis in a polystyrene polymer is a transition point. However the glass transition point or T, is the temperature at which all molecular movement including mobility about the bonds in the backbone of the polymer becomes frozen. 

It was pointed out in an earlier section that the viscoelastic properties are strongly related to the frictional properties of the polymers. Ferry has described some typical examples of viscoelastic responses of various polymers. The factors upon which the response depends are the molecular weight, the structure (amorphous or crystalline), the test temperature in relation to the glass transition temperature and the type and amount of foreign material which is usually added in commercial preparations for obtaining certain additional desirable properties. 

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