Technical Abstract: Polydiacetylene (PDA), a unique conjugated polymer, has shown its potential in the application of chem/bio-sensors and optoelectronics. In this work, we first infiltrated PDA monomer (10, 12-pentacosadiynoic acid, PCDA) melted into the anodized aluminum oxide template, and then illuminated the infiltrated template with UV light to initiate the polymerization of PCDA. After etching away the aluminum oxide templates, we obtained solid poly-PCDA nanofibers. We found that, even tightly confined in a template, pores with a diameter as small as ~35 nm, PCDA crystals were able to be polymerized through a solid polymerization mechanism induced by UV light. Poly-PCDA nanofibers, both in the released form and embedded in the template, showed characteristic blue to red color change in sensing the exposure of organic solvents and temperature increases, and the red colored fibers possessed strong fluorescence. Moreover, poly-PCDA nanofibers were highly crystalline, and oriented favorably in a certain direction due to the confinement of nanopores, as demonstrated by X-ray diffraction texture analysis and orientation distribution analysis by scanning confocal optical microscopy.