Star polymers in a 0 and poor solvent

At the 0 point, the self-repulsion of the monomers, due to the excluded volume, is just compensated for by the interactions with the solvent. While this tricritical point is well understood for linear chains, less is known about the properties of stars at Tff. Candau et alP assumed that at Tq all the arms can interpenetrate each other completely. This means that all virial coefficients vanish and the size of the star is given by the Zimm-Stockmayer equation. 

While this is obviously an oversimphfication, it turns out to work quite well. As seen from eq. (9.17), the Daoud and Cotton scaling argument gives g f) r j f However since at Tq, the second virial coefficient between a 

To study the importance of three body interactions on stars, Batoulis and Kremer carried out high precision MC simulations of linear and star polymers on the fee lattice for 1 / 12 and N 900 using the inverse restricted sampling method. These simulations extended earUer simulations on smaller stars by Mazur and McCrackin. They found that Tq 

Where available g was determined from extrapolations for large molecular weight when possible, otherwise the data for the longest arms were used.  

The monomer density p r) for a solvent was found by Grest to agree nicely with the scaling prediction,/As in a good solvent the free ends are excluded from the center of the star. The distibution of free end for stars with/= 20 for a good, 0 and poor solvent is shown in Fig. 9.8(b). Note that the distributions are approximately symmetric, with a slight shift towards 

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