Controlling nanoparticle dispersion in polymer matrices has been and is still a long-standing issue, and directly impacts the performance of the materials. In the majority of instances, simply mixing nanoparticles and polymers leads to macroscale aggregation, resulting in deleterious effects. Here, we report a new method, reaction-induced phase transitions (RIPT), to dictate the nanoparticle dispersion state during the polymerization of nanoparticle/monomer mixtures. Specifically, oleylamine-functionalized gold nanoparticles (AuNP) are first synthesized in a methyl methacrylate (MMA) solution, and then subsequently polymerized using a free radical polymerization initiated with azobisisobutyronitrile (AIBN) to create hybrid AuNP and poly(methyl methacrylate) (PMMA) materials. The resulting products are easily pressed to obtain bulk films with nanoparticle dispersions consisting of well-dispersed, particle strings, particle clusters, and connected nanosheets. Polymerizations are performed at various temperatures (T) and MMA volume fractions (ΦMMA) to systematically influence the final nanoparticle dispersion state. During the polymerization of MMA, the initially homogeneously mixed AuNP/MMA mixture undergoes phase separation via nucleation and growth or spinodal decomposition, which dictates the resulting particle dispersion state. The reported results highlight how reactive processing enables the synthesis of versatile and scalable hybrid materials with programmed nanoparticle dispersion.

Dictating nanoparticle organization in polymer matrices during reaction-induced phase transitions

ACS Fall 2021

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