Formation mechanism of zigzag patterned P(NIPAM-co-AA)/CuS composite microspheres by in situ biomimetic mineralization for morphology modulation

Poly(N-isopropylacrylamide-co-acrylic acid)/copper sulfide (P(NIPAM-co-AA)/CuS) composite microspheres with variable zigzag patterned surfaces have been synthesized by employing an in situ biomimetic mineralization reaction between H2S and Cu2+ immersed in P(NIPAM-co-AA) microspheres for morphology modulation. The morphology and composition of the P(NIPAM-co-AA)/CuS composite microspheres with zigzag patterned surfaces prepared in different conditions were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FT-IR). The polymeric microgels swelled by Cu(Ac)2 solution after freeze-drying treatment were of porous structure, indicating that there were polymeric frameworks and rich-water domains in the microgels before the deposition. Furthermore, due to the limited uneven deposition of metal sulfide on the polymeric skeleton of the hydrogel surface, the surface polymeric skeleton will be anisotropically shrunk when the composite microspheres lose water and shrink, thus forming a wrinkle pattern on the surface of the composite microspheres. The factors affecting the deposition amount and distribution of metal sulfide will affect the zigzag patterned morphology. Based on the experimental results, a formation mechanism of the P(NIPAM-co-AA)/CuS composite microspheres with zigzag patterned surface, "the deformed shrinkage of the surface texture", has been proposed. The formation mechanism of the surface morphology in the composite microspheres is helpful for understanding and controlling the process of mineralization, for preparing materials expected by controlling the experiment conditions, and for expanding the application of the composites.