Process intensification technologies based on novel reactors have been considered to be the most promising progress paths for developing more efficient chemical processes. In this work, the synthesis of poly(9,9-dioctylfluorene-alt-benzothiadiazole), abbreviated as F8BT, was achieved via Suzuki cross-coupling polymerization in a rotating packed bed (RPB) reactor maintained in an oxygen-free environment. The synthesized F8BT has a number average molecular weight of 35.2 kDa, a polymer dispersity index of 2.47 and double band absorption and yellow-green photoluminescence properties. An aqueous dispersion of F8BT nanoparticles was then prepared by solvent–antisolvent recrystallization in an external circulation RPB reactor, and spherical nanoparticles with an average particle size of 175.6 nm and a particle dispersion index within 0.2 were obtained. The nanoparticles, which appear yellowish green in color under 365 nm excitation, were uniformly incorporated into polyvinyl alcohol by virtue of the compatibility brought about by hydrogen bonding to obtain PVA composite films containing F8BT nanoparticles. The composite film has a shape memory function, and the irreversible shape change process from the initial “closure” to the final “blooming” is completed in about 15 min at an ambient temperature of 20 °C and 60% relative humidity. It is expected to be used as an optical functional device to monitor the cold chain.