New method proposed for an efficient structure

image: The related result was posted on Langmuir as a cover story
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Credit: ZHANG Wei

Small particle number (CM) non-spherical clusters have potential applications in coatings, self-assembly of materials, biomedical diagnostics. The sphere has the smallest area under a certain volume, that is, the total Gibbs free energy of the surface is the lowest. Therefore, most nanoparticles have a spherical shape, which leads to difficult preparation of non-spherical CMs.

In an article published on Langmuir, a new method suggested by scientists at the Hefei Institutes of Physical Science (HFIPS), Chinese Academy of Sciences (CAS) solved this problem. In their recent research, the team proposed a synthetic pot pathway to prepare colloidal molecules (CMs) demonstrated in various morphologies such as popcorn, CO2, NH3, CH4.

“Our method, based on nucleation and growth of the surface of the seeds, aimed to prepare MCs of different morphologies in the same pot, so we called it the one-pot method”, explained Professor TIAN Xingyou, who led the team. “The mechanism allowed the synthesis of CM without any seed pretreatment or monomer swelling process, which holds great promise for production on an industrial scale.”

He further explained the process of forming the different CMs. The surface of the seeds, prepared with a soap-free emulsion, was coated with initiators which could be used for a subsequent styrene polymerization reaction to initiate the polymerization of the monomers. It formed the intermediate multi-core nanoparticles. As for the popcorn-like CMs, it is when the crosslinking agent divinylbenzene (DVB) and styrene (ST) were added simultaneously to the seed dispersion, the DVB would crosslink the PS chain to form a structure of 3D network and hamper the fusion of the PS cores. When the researchers simply added styrene or there is a one hour delay for adding the DVB crosslinking agent compared to adding styrene, AXn-type CMs could be obtained. This is mainly because DVB, which was not introduced or introduced later, could not prevent the process of fusing multiple nuclei of the PS at an early stage.

“This proved that the shape and size of CMs can be adjusted by changing the order of addition and content of ST and DVB,” TIAN Xingyou said, “This provided a good basis for self-assembly. . “

According to this research result, seed pretreatment and monomer swelling can be avoided. This dramatically shortens the manufacturing time. The discovery can take the manufacturing of CMs in a salable and reliable direction.

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