Molecular Models for Solutions

Simha [53] made the first attempts to model the transition from a dilute to a concentrated solution. He assumed that in the range from l c[r ] 10 the coils interpenetrate and form a homogeneous network. On the basis of the so-called scaling laws a theory has been developed which allows for the prediction of the influence of c and the solvent power on the screening length [54, 55]. This theory is founded on the presumption that above a critical concentration, c, the coils overlap and interpenetrate. Furthermore it is assumed that in a thermody- 

Fig-1- Bueche plot for various narrowly distributed polystyrene samples in toluene (A) Mw= 

Graessley showed [40] that for a complete description of polymer fluids over the whole concentration range, i.e. from volume fraction f)— 0 to )=1, in a thermodynamically good solvent, five distinct states of solution must be taken into account. These five states of solution are  

The range of validity of a semi-dilute network lies between the two critical values c (transition between semi-dilute particle solution and semi-dilute net- 

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