Investigation of the Colorimetric Transition in Polydiacetylene Nanovesicles Induced by α-Cyclodextrin and the Inhibitory Role of Triblock Copolymer Addition

Polydiacetylene (PDA) nanovesicles are widely recognized as versatile chromatic sensing platforms, exhibiting a visible blue-to-red colorimetric transition in response to stimuli such as temperature, pH, and molecular recognition events. Alpha-cyclodextrin (α-CD) is known to interact with PDA vesicles, inducing this transition through host–guest inclusion at the vesicle interface. Here, we demonstrate that incorporating the EO–PO–EO triblock copolymer L64 into PDA suspensions enables precise modulation of this α-CD-induced chromatic response. Increasing L64 concentration progressively suppresses the blue-to-red transition, as the copolymer competes with PDA headgroups for α-CD inclusion. Isothermal titration calorimetry revealed that α-CD exhibits a stronger affinity for L64 (K = 11,300) than for PDA vesicles (K = 4,000), with both processes being spontaneous (ΔG° ≈ –21 kJ mol⁻¹) and entropy-driven. Importantly, the self-assembled PDA vesicular structure remains intact, as confirmed by phase separation and optical analyses, highlighting that the colorimetric inhibition arises from supramolecular competition rather than structural disruption. This work introduces a new supramolecular strategy to negatively regulate PDA affinity-chromism through competitive inclusion complexation with biocompatible triblock copolymers, offering a robust and tunable route for developing responsive and safe chromatic sensors.