Continuous Preparation of Hollow Polymeric Nanocapsules Using Self-Assembly and a Photo-Crosslinking Process of an Amphiphilic Block Copolymer.

Xuan Nguyen,Taeheon Lee,Hyeong Jeon,Van Nguyen,Jeung Go,June Huh,Hyun-Jong Paik,Dong Park

doi:10.3390/molecules22111892

Xuan Nguyen, Taeheon Lee + Show 6 more

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https://doi.org/10.3390/molecules22111892

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Abstract

This paper presents a fabrication method of hollow polymeric nanocapsules (HPNCs). The HPNCs were examined to reduce light trapping in an organic light emitting diodes (OLED) device by increasing the refractive index contrast. They were continuously fabricated by the sequential process of self-assembly and photo-crosslinking of an amphiphilic block copolymer of SBR-b-PEGMA, poly(styrene-r-butadiene)-b-poly(poly(ethylene glycol) methyl ether methacrylate) in a flow-focusing microfluidic device. After the photo-crosslinking process, the produced HPNCs have a higher resistance to water and organic solvents, which is applicable to the fabrication process of optical devices. The morphology and hollow structure of the produced nanocapsules were determined by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Also, their size control was examined by varying the ratio of inlet flow rates and the morphological difference was studied by changing the polymer concentration. The size was measured by dynamic light scattering (DLS). The refractive index of the layer with and without the HPNCs was measured, and a lower refractive index was obtained in the HPNCs-dispersed layer. In future work, the light extraction efficiency of the HPNCs-dispersed OLED will be examined.

Highlights

Organic light emitting diodes (OLED) have drawn attention for display applications as a thin film light source
The process ofPreparation fabricating the hollow polymeric nanocapsules (HPNCs) was conducted in a flow-focused microfluidic channel
This work continuous online process to produce. They consisted of polymer shells cavities increasethe therefractive refractiveindex index contrast contrast for for the consisted of polymer shells andand air air cavities to to increase the application of

Summary

Introduction

Organic light emitting diodes (OLED) have drawn attention for display applications as a thin film light source. The problem of light trapping in OLED devices has been addressed. Thirty percent of the light is reflected in the interface of glass and air and only 20% of the generated light can escape as useful light. Since the largest portion of light is trapped within the organic-ITO (Indium Tin Oxide) layer, as shown, the most efficient method to improve outcoupling efficiency (hereafter, OCE) has been introduced to insert optical scattering structures in close proximity to the ITO layer [1,2,3,4]. Various optical scattering structures have been developed. A high index grating of silicon nitride was used to extract the trapped light and fabricated by using nano-imprinting technology [5,6]

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