Coil-Globule Transition Versus Aggregation

we describe and compare the results of simulations for two multichain systems corresponding to alternating and protein-like HA copolymers [212], The multichain systems consisting of 127-unit copolymers were simulated for the range of the effective interaction parameter / (which is similar to the Flory-Huggins parameter) under solvent conditions when single chains can form strongly collapsed conformations. 

In Fig. 42, we show the ratio R2P/R2 U (i 2n and R2V are the partial mean-square radii of gyration calculated separately for hydrophobic and hydrophilic beads) as a function of the interaction parameter /. We see that this ratio is an increasing function of /. Qualitatively the same picture is observed for isolated chains. Such behavior is due to the fact that, as the attraction 

The calculated values of AG are presented in Fig. 43 as a function of the interaction parameter x As seen, lowering the temperature, or equivalently, 

Moreover, the thorough analysis of globular conformations shows that this layer is almost absent near the faces of the cylinder [212]. This facilitates the formation of multiglobular aggregates in the solution of regular copolymers. 

These facts explain the more expressed tendency of regular copolymers toward aggregation. 

Generally speaking, the reason for this behavior is simple. It is known that low-molecular-weight surfactants dramatically increase the stabiUty of polymers and are widely used to prevent aggregation in polymer solutions. In the HA model, surfactants , i.e., amphiphihc A groups, are incorporated into the polymer chain, thus ensuring the stabihzing effect. From the tempera- 

---