Mussel-Inspired Thermosensitive Polydopamine-graft-Poly(N‑isopropylacrylamide) Coating for Controlled-Release Fertilizer

A thermoresponsive release multi-element compound fertilizer was first reported on the basis of a polydopamine-graft-poly­(N-isopropylacrylamide) bilayer coated on a salty core by a combination of dopamine chemistry and surface-initiated atom transfer radical polymerization techniques, and the control of nutrient release in response to the environmental temperature was investigated. The successful synthesized stimuli–responsive fertilizers were confirmed by transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and gel permeation chromatography (GPC). The release of elements from fertilizer was determined by an inductively coupled plasma (ICP) emission spectrometer. The thermosensitive fertilizers exhibit outstanding stimuli–responsive permeability to encapsulated nutrients, and the release rate of coated elements can be tailored by the ambient temperature. They can release nutrients easily at T < lower critical solution temperature (LCST) but slow at T > LCST. This strategy of grafting thermoresponsive polymer brushes on polydopamine (Pdop)-coated substrates is useful to prepare a stimuli–responsive release system, which can adjust the release rate according to different conditions, and will be effective and promising in the research and development of a stimuli-sensitive controlled-release system.