Associative Polymers with Controlled Sticker Placement: How Reversible Bond Distribution and Density Govern Polymer Dynamics

Precise monomer placement in polymers provides a powerful strategy to tailor material properties and function. Associative polymers represent a minimal yet versatile platform, incorporating reversible "stickers" that mediate interchain and intrachain interactions. However, it remains unclear how sticker density and distribution govern structure, dynamics, and macroscopic properties of associative polymers. By developing a model system with hydrogen-bonding stickers, we show that randomly distributed stickers neither form clusters nor change flow properties, whereas stickers placed at chain ends drive nanocluster formation even at low concentrations. Adding more end-stickers produces a rubbery plateau spanning eight decades in frequency with two distinct relaxation timescales, corresponding to segmental relaxation within nanoclusters and dissociation of sticky ends from nanoclusters, in contrast to the single plateau predicted by the classic sticky Rouse model. These results demonstrate that sticker distribution dictates whether associative polymers undergo nanocluster formation or microphase separation, while significant alterations in dynamics and viscoelasticity require both sticker aggregation and thermomechanical stability of associated domains. Our findings resolve a longstanding debate on associative polymer dynamics and provide molecular design rules for programmable soft materials.