Morphological and phase behaviors of symmetric diblock copolymers: insights from coarse-grained molecular dynamics simulations

This study investigates the self-assembly behavior and morphological stability of symmetric AB diblock copolymers via coarse-grained molecular dynamics simulations. We focus on the effects of segmental incompatibility associated with interfacial interaction strength ( $${\varepsilon }_{(A,B)}$$ ), interaction range ( $${r}_{c,(B,B)}$$ ), and degree of polymerization (N) on the system morphology. By systematically varying these Lennard-Jones parameters governing intermolecular interactions, we quantify the resulting morphologies using domain spacing (D), the peak intensity of the structure factor S(q*), and the correlation length ( $${\xi }_{\text{fit}}$$ ). Our results reveal that enhanced B-block cohesive interactions by increasing the range of intermolecular interactions ( $${r}_{c,(B,B)}$$ $$\ge$$ 2.0) stabilize lamellar structures by suppressing curvature-induced instabilities and preserving domain periodicity, even at high miscibility between the A and B blocks. Correlation analysis reveals that longer chain lengths and extended cohesive ranges synergistically enhance long-range ordering and interdomain connectivity. This study establishes a quantitative computational framework linking intermolecular interaction parameters with microphase separation, offering a practical strategy for exploring nanoscale morphology in block copolymers via molecular simulations.