The Fe
3O
4 NPs are encapsulated within the PDVB network, rendering magnetic responsive behavior. Magnetization of the composites is determined by the content of Fe
3O
4. In the presence of 0.05% of Fe
3O
4 NP, the amount of thin nanofibersreaches maximum while exhibiting sufficient magnetic performance. The thin PDVB nanofiber remains the similar hydrophobic as the thick PDVB nanofiber (Fig. S2-1 in Supporting information). The PDVB composite nanofibers keep the brown color when emerging in acidic water, while water keeps colorless (Fig. S2-2 in Supporting information). No leakage of Fe
3O
4 occurs, ensuring the composite nanofibers are stable in water treatment. In comparison, the Fe
3O
4 NPs absorbed PDVB nanofibers become white from the original brown, and water becomes yellow (Fig. S2-3 in Supporting information). The absorbed Fe
3O
4 NPs are completely dissolved in acidic water. Similar with our previous report, the current thin PDVB composite nanofibers can effectively absorb the representative chemicals forming the gels (
Fig. 3a). As shown in Table S1 (Supporting information), the thin PDVB nanofiber displays higher absorption capability for all the chemicals. In comparison, the PDVB dendrite exhibits weaker absorption capability. The interconnected network of the PDVB nanofibers and toluene can be distinguished when visualized at different wavelength under confocal laser scanning microscope. At the 488 nm fluorescence channel, the network of PDVB nanofibers displays red (
Fig. 3b1). At the 559 nm fluorescence channel, the background displays green corresponding to the toluene phase at the interstitial voids within the network (
Fig. 3b2). The high gelation capability of the nanofibers is promising to collect chemical spills from water. Dyed toluene was used as the model chemical spill on water (
Fig. 3c1). Upon adding the PDVB nanofibers, toluene was captured forming a gel (
Figs. 3c1–2). The collection was too fast within 30 s to monitor the absorption process. The gel was completely removed with a magnet (~0.8 T) (
Fig. 3c3). Neither toluene nor gel fragment was residual in water. The saturated adsorption capacity for toluene was 24.0 mL/g. The magnetic PDVB nanofiber was easily regenerated by squeezing and then evaporation of the chemicals at high temperature. When the temperature is close to the boiling point of the organic solvent, most of the solvent can be removed. The saturated adsorption capacity was slightly decreased to 22.9 mL/g after 15 cycles (
Fig. 3d). The magnetic collection capability of the composite nanofibers keeps stable even after stored in air for one year.