||Development of efficient sensors utilizing conjugated polymer as sensing matrices has gained much attention among many research scientists. For example, Polydiacetylenes (PDAs) display several interesting structural and optical properties. Mixture of PCDA monomer and lipid with suitable ratio can prepare PDAs vesicle. Benzoxazole emitting blue fluorescence was encapsulated inside the PDAs vesicle. The PDAs backbone would be responsible for red fluorescence. We used Fluorescence Resonance Energy Transfer (FRET) between PDAs backbone and encapsulated dye. Blue fluorescence of encapsulating dye decreased, while red fluorescence of PDAs backbone increased about four-fold because of energy transfer from the dye to the PDAs backbone. PDAs were destroyed by controlling pH and solvent. Therefore, encapsulating dye in PDAs vesicle release to PDA solution. As a result, blue fluorescence increased and red fluorescence decreased because of FRET phenomenon not occurred.