A Simple Synthesis of Higher Refractive Index Polymeric Nanocomposite Containing the Pendant ZnS Nanocrystals Capping Different Amount of Mercaptoethanol

Xinxin Li,Jinku Xu

doi:10.1155/2020/7350367

Xinxin Li, Jinku Xu

Open Access

https://doi.org/10.1155/2020/7350367

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Abstract

In this paper, three kinds of ZnS NPs capping different amount of mercaptoethanol (ME) were synthesized, and the effect of capping amount on ZnS NPs was studied, indicating that the capping amount of ME on ZnS surface decreases, while ZnS size increases as the decrease of added capping agent in synthesis process, and ZnS NP capping middle amount of ME (~27.7 wt%) shows a highest apparent refractive index (RI) value. ZnS NPs were composited into polymeric matrices by a simple “one-step” thermocuring method characterized by adding a small amount of functional monomer of glycidyl methacrylate (GMA) and solvent of N,N-dimethylformamide (DMF) The reaction mechanism, studied by 1H NMR spectra, indicates that the epoxy of GMA monomer can be easily opened and chemically grafted on ME-capped ZnS surface under the catalysis of DMF, and then copolymerized with other monomer. By the route, ZnS NPs can be composited into pure poly(N,N-dimethylacrylamide)-type (DMA-type), DMA-type copolymer, and DMA-free matrices to fabricate transparent films, and its RI value can be improved by either optimizing capping amount on ZnS surface or increasing ZnS content in the nanocomposites. The RI value of resulting dried nanocomposites can be improved to 1.764 by compositing 80 wt% ZnS capping middle amount of ME.

Highlights

High refractive index (RI) optical materials have extensive applications in lenses, prism, waveguides, and light-emitting diodes (LEDs) [1,2,3], and great progress has been made to synthesize high RI materials
We found that the functional monomer of glycidyl methacrylate (GMA) plays an important role for its transmittance, e.g., the DMA-type copolymeric nanocomposite hydrogel, without adding functional monomer of GMA, exhibits serious irregular nanoparticle aggregation
The amount of capping mercaptoethanol on ZnS surface can be controlled by adjusting the amount of mercaptoethanol added in the synthesis process, and increased capping amount helps to decrease the size of ZnS nanocrystals

Summary

Introduction

High refractive index (RI) optical materials have extensive applications in lenses, prism, waveguides, and light-emitting diodes (LEDs) [1,2,3], and great progress has been made to synthesize high RI materials. Two main approaches have been developed to composite inorganic nanoparticles in polymeric matrices including either in situ formation of inorganic NPs in the polymeric matrix or bulk polymerization of organic monomer solution in the present of premade nanoparticles The latter approach is usually proved to be more effective, because it can provide full synthetic control over both the nanoparticles and the polymeric matrices. Two methods can be used to reduce particle aggregation either bonded covalently nanoparticles on the polymeric skeleton or embedded physically nanoparticles in special polymeric matrices that interact with the nanoparticles The former method can ensure a more homogeneous intermixing.

Experimental Section

Synthesis of ME-Capped and Polymerizable-Group-Capped ZnS NPs

Results and Discussion

Conclusions