POSS chain-end anchoring simultaneously enhances structural order and induces reduction in lamellar spacing in PTFEMA-b-PS block copolymers

The self-assembly of block copolymers (BCPs) into ordered nanostructures is often limited by kinetic barriers, particularly in high-segregation systems. Here, a chain-end engineering strategy is developed by introducing a rigid polyhedral oligomeric silsesquioxane (POSS) moiety as an anchoring group. Poly (2,2,2-trifluoroethyl methacrylate)-block-polystyrene (PTFEMA -b- PS) copolymers were synthesized and end-functionalized with amino-modified POSS to yield PTFEMA -b- PS-BPOSS. Small-angle X-ray scattering revealed that POSS significantly enhances microdomain ordering and induces a measurable contraction in interdomain spacing. The rigid POSS anchor restricts chain-end mobility, increases interfacial tension, and promotes compact chain packing with sharper phase boundaries. Isothermal annealing confirmed accelerated ordering and reduced defect density. This work highlights the crucial role of rigid chain-end anchoring in directing high-χ BCPs self-assembly and provides a versatile molecular design strategy for creating nanostructures with superior periodicity and thermodynamic stability. • POSS end-groups contract lamellar spacing by ∼4.5%, showing clear nanocontraction • Rigid POSS anchors restrict mobility, promote stronger interactions and tight packing. • Computations show POSS lowers vibrational energy, stabilizing the polymer system.