Surface‐Induced Donor–Acceptor Charge‐Transfer Interaction in Crystallization‐Driven Two‐Dimensional Assembly of Poly(L‐Lactide) and Its Impact on Piezoelectric Performance

ABSTRACT Precise 2D architectures with tailorable surface properties from organic soft materials remain a formidable scientific challenge. This work demonstrates crystallization‐driven self‐assembly (CDSA) as a simple yet powerful strategy to obtain discrete 2D microcrystals from biocompatible semicrystalline chromophore end‐capped poly(L‐lactide) (PLLA) scaffolds, serving as well‐defined 2D templates for supramolecular engineering of surface properties via donor‐acceptor (D‐A) charge‐transfer (CT) interactions. As a representative case study, we show that CDSA yields diamond‐shaped 2D PLLA platelets with electron‐deficient, cationic naphthalene diimide (NDI) acceptors pre‐organized on the 2D surface. This enables electrostatically induced D‐A interactions with anionic electron‐rich dihydroxynaphthalene (DHN) guests, allowing exploration of their functional utility in piezoelectric (PE) energy harvesting. The synergistic effect of inherently non‐centrosymmetric PLLA chain packing and CT‐interactions on the 2D surface results in efficient macroscopic polarization switching, leading to prominent piezoelectricity (d ₃₃ ∼14 pm/V) without poling. This enhanced PE response was exploited for micropower energy harvesting as demonstrated by a piezogenerator functionality (output V _oc ∼ 1.30 V and J _sc ∼ 0.5 µA/cm ² ), showing potential proof‐of‐concept application as an efficient physiological sensor. Multiple control experiments confirm that without such well‐defined 2D architectures, PE functions do not emerge, establishing CDSA‐engineered PLLA 2D platforms as emerging functional materials for energy harvesting beyond structural aesthetics.