Investigation of Core Density in Single Polymeric Globules Using Molecular Dynamics Simulations

Formation of single polymeric globules occurs via a coil-to-globule transition when temperature or solvent qualities change, representing a molecular phase transition unique to polymeric systems. The underlying principles of the formation of globules and their distinctive conformational properties have been extensively studied due to their funda-mental significance in polymer science and potential applications in developing novel polymeric materials. According to Flory-type theory, the formation and conformation of globular polymers are governed by a balance of two-body and three-body interactions among monomers, resulting in a core density of the globules invariant with the degree of polymerization and dependent only on temperature. In this study, we carry out extensive molecular dynamics (MD) simulations using a primitive single polymer model to validate theoretical predictions regarding the core density behaviors of single-polymeric globules. Our results demonstrate that the primitive model employed in this study accurately captures the con-formational changes of a single polymer during the coil-to-globule transition observed in experiments. We observe that the core density of a single polymer increases as the polymer adopts a globular and compact conformation. Notably, when varying the degree of polymerization of a single polymer from 100 to 1200, we find that the core density at various tem-peratures remains unaffected in stable globules. These findings are consistent with the previous prediction of Flory theory, highlighting the importance of the two-body and three-body energetic contributions to the conformational free energy of globular polymers in governing their conformational properties.