Preparation And Properties Of SDS Micelle-based Temperature-sensitive Composite Hydrogels

Thermochromic smart windows were a kind of devices that could change their optical properties in response to the stimulation of external temperature,thereby adjusting the transmission of light.It can achieve the goal of energy conservation while maintaining a comfortable indoor temperature.In recent years,thermochromic smart windows have shown broad application prospects in the field of building energy conservation owing to their advantages of reasonable stimulation and no active intervention and additional energy consumption.As a warm-blooded animal,human beings require a suitable living environment temperature,too high or too low ambient temperature will have an impact on the comfort of the human bodies.Therefore,a reasonable phase transition temperature was a key performance index for thermochromic smart windows.However,the response temperature of most thermochromic smart windows was generally higher than the comfortable temperature of the human body,and the response temperature was also difficult to adjust,which limits its application in real life.Hence,it was crucial to prepare smart windows with high transparency,reasonable and adjustable thermochromic temperatures,which could enhance their performances.Based on this,two kinds of thermochromic hydrogels with reasonable response temperature were prepared and used in the fields of smart windows,anti-counterfeiting and information encryption.The main research contents were as follows:（1）Preparation and application of T_k-adjustable temperature-sensitive SDS micelles-based thermochromic hydrogelsThermochromic hydrogel（Pgel）with a reasonable and adjustable thermochromic temperature were prepared by introducing polyethylene glycol（PEG）,sodium dodecyl sulfate（SDS）and potassium tartrate（PTH）into cross-linked three-dimensional polyacrylamide（PAM）networks.The thermochromic temperature（T_k）can be precisely adjusted between 16-34°C by changing the amount of PTH,and the T_k can be as low as 16°C.The hydrogel could complete the transition from transparent to opaque in an extremely narrow temperature range（1°C）,and achieve rapid optical response in 50 s.In addition,Pgel has a unique light-selective transmittance under room temperature or high temperature environments,with a high transmittance（>85%）for visible light,and excellent blocking performance for infrared light,which was conducive to indoor lighting and thermal insulation.Solar light simulation experiment indicated that compared with ordinary glass windows,Pgel hydrogel smart window model room could achieve insulation effect of 5.6°C.At low temperatures,the hydrogel was opaque,and almost all wavelengths of light were blocked,which was good for privacy protect at cold nights.In addition to passive temperature control,the"transparent opaque"transition of Pgel hydrogel could be actively controlled by regulating the current.The prepared hydrogel-based smart windows have excellent cycling stability and fast transparency switching characteristics.And the Pgel hydrogels can be used in the fields of intelligent temperature monitoring and home safety protection.This kind of Pgel hydrogel with reasonable and adjustable thermochromic temperature provides a feasible and promising method for constructing multi-functional thermochromic hydrogel smart windows.（2）Preparation and properties of SDS micelles/PNIPAM composite hydrogels with bidirectional optical responseA kind of smart composite hydrogels（BSW）with unique bidirectional optical response were prepared by introducing the micelles formed by the hydrogen bond interaction of SDS and PTH into the temperature sensitive poly（N-isopropylacrylamide）（PNIPAM）networks.BSW showed two abrupt changes in optical properties between 0-50°C with upper critical solution temperature（UCST）and lower critical solution temperature（LCST）.By adjusting the amount of PTH,the UCST of BSW could be accurately adjusted between 9.4-25.5°C,while changing the amount of SDS allowed the LCST of BSW to vary between 25.5-50°C.In the temperature range between UCST and LCST,BSW was transparent with high light transmittance（>90%）and visible light transmittance(T_lum=91.31%).When the temperature was higher than LCST or lower than UCST,BSW became opaque due to the increased interfacial scattering caused by internal phase separation.BSW has a remarkably high solar modulation rate(?T_sol,_UCST=76.34%,?T_sol,LCST=76.75%)and visible light modulation rate(?T_lum,_UCST=90.95%,?T_lum,_LCST=91.21%).This excellent optical modulation ability was essential for smart windows.Thermal insulation performance test indicated that BSW achieved a cooling effect of 23.2°C lower than that of ordinary windows.It was worth noting that BSW can selectively block most of the infrared and ultraviolet light from solar radiation,while allowing visible light to pass through.In addition,bidirectional optical response BSW hydrogels materials were applied to the fields of information encryption and temperature monitoring,expanding the application range of as-prepared thermochromic materials.Compared to traditional single-response smart windows,the bidirectional optical response characteristics exhibited by BSW were more in line with the practical needs of human beings for building temperature regulation,providing a feasible strategy for building a new generation of smart windows.