Preparation and Properties of Thermoresponsive P(N-Isopropylacrylamide-co-butylacrylate) Hydrogel Materials for Smart Windows

Jae-Hyung Park,Dong-Jin Lee,Han-Do Kim,Ji-Won Jang,Young-Hee Lee,Sang-Hui Park,Il-Jin Kim,Jae-Hak Sim

doi:10.1155/2019/3824207

Abstract

Thermoresponsive polymers that exhibit phase transition in response to temperature change can be used as material for smart windows because they can control solar light transmission depending on the outside temperature. The development of thermoresponsive polymers for a smart window that can be used over a wide temperature range is required. Therefore, to obtain smart window materials that can be used at various temperatures, three-dimensional thermoresponsive P(NIPAm-co-BA) hydrogels were prepared by free radical polymerization from main monomer N-isopropylacrylamide, comonomer butyl acrylate, and crosslinking agent N,N′-methylenebisacrylamide (MBAm) in this study. This study examined the effect of BA content on the lower critical solution temperature (LCST) and the solar light transmittance of crosslinked P(NIPAm-co-BA) hydrogel films. The LCST of hydrogel films was found to be significantly decreased from 34.3 to 29.5°C with increasing BA content from 0 to 20 mol%. It was found that the transparent films at T=25°C (T<LCST) were converted to translucent films at a higher temperature (T=45°C) (T>LCST). These results suggested that the crosslinked P(NIPAm-co-BA) hydrogel materials prepared in this study could have high potential for application in smart window materials.

Highlights

In order to block sunlight, devices such as curtains and blinds have been used, but smart window technology is emerging that can adjust light freely according to ambient temperature
Smart windows are being studied with liquid crystal displays (LCDs) and electrochromic (EC) devices, but they are difficult to commercialize because they require additional power and expensive installation costs
This study focused on the effect of butyl acrylate (BA) content on the lower critical solution temperature (LCST) and light transmittance difference (ΔT) of the transparent/opaque phase of copolymer hydrogel and confirmed the applicability of synthetic copolymer hydrogel to a smart window

Summary

Introduction

In order to block sunlight, devices such as curtains and blinds have been used, but smart window technology is emerging that can adjust light freely according to ambient temperature. Smart windows are being studied with liquid crystal displays (LCDs) and electrochromic (EC) devices, but they are difficult to commercialize because they require additional power and expensive installation costs. Stimuli-responsive polymers are characterized by the reversibility of their chemical or physical properties due to external stimuli such as temperature, light, pH, and current [6, 7]. A thermoresponsive (temperature-responsive) polymer with a temperature stimulus source is characterized by reversible sol-gel phase transition or volumetric phase transition at a specific temperature and is used in various fields such as drug delivery systems, sensors, and separation membrane [8,9,10,11]. The specific temperature at which the phase transition occurs is called the lower critical solution temperature (LCST)

Methods

Results

Conclusion