Preparation And Properties Of Thermal Phase-Transition Hydrogel

Hydrogel was a new type of the functional polymer material with high water content and excellent biocompatibility,and the potentially applicational value of hydrogel has received widespread attentions.Because of the adjustable network structure,hydrogel could simultaneously possess significant abilities such as mechanical property,transparency and conductivity under certain conditions used in many fields including light regulation,temperature monitoring,electrodes,sensor,bionic materials,etc.Thermal phase transition material is a functional material that could control the spectrum as temperature changes,which was used in many fields,such as smart windows,smart roofs,automotive glass,etc.Vanadium dioxide was a representative inorganic thermal phase transition material,but the high phase transition temperature limits applications in the daily life.Poly(N-isopropylacrylamide)was a polymer with the thermal phase transition ability,but the temperature adjustment was limited by phase transition.Therefore,it was significant to obtain a novel material with inexpensive,efficient and the ability of adjusting the phase transition temperature.In this paper,the following researches were conducted.In the first part,a new type of thermal phase transition hydrogel was obtained by introducing potassium tartrate hemihydrate and sodium dodecyl sulfate into a chemically crosslinked polyacrylamide network.The temperature-sensitive micelles were formed by hydrogen bonds between potassium tartrate hemihydrate and sodium dodecyl sulfate.The thermal phase transition properties of the hydrogel were achieved by adjusting the size of the micelles as the temperature changed.By changing the content of potassium tartrate hemihydrate,the phase transition temperature could be controlled between 25°C and 35°C.In the second part,a new thermal phase transition hydrogel was obtained by introducing potassium tartrate hemihydrate and sodium dodecyl sulfate into the network of hydrophobically associated polyacrylamide,which enhanced the mechanical properties of the hydrogel.Moreover,the micelles were fixed in the hydrophobic association network so that the transmittance of the hydrogel was improved.A new type of smart window was prepared using indium tin oxide film,hydrogel and glass that the visible and near-infrared shielding reached 88.3% and 85.4% at ambient temperature,respectively.After applied voltage,the visible and near-infrared light were allowed to pass through the smart window and the transmittance of the visible light beyond 70%.During the 100 power-on/off cycles,there was no significant change in light transmittance.In the third part,on the basis of the second part,the different electrolytes were introduced into the hydrogel,and the phase transition temperature could be accurately adjusted between 5°C and 53°C during the temperature cycle with an accuracy of 1°C.Moreover,it has almost no effect on the optical performance of the hydrogel in the process of adjusting the phase transition temperature.Therefore,the common problems of narrow range of phase transition temperature and low accuracy in thermal phase transition materials were solved.This strategy,driven by hydrogen bonds between organic salts and surfactants,not only provided new design-thinking for the preparation of thermal phase transition materials materials,but also the low-cost,high-efficiency and adjustable phase transition temperature were significance for the development of thermal phase transition materials.