Study On The Synthesis And Properties Of Acrylic Acid Series Sensitive Hydrogel

In recent years, considerable research attention has been focused on the environment-sensitive hydrogels (intelligent hydrogels) because they possess great potential applications in many aspects, including drug delivery system, enzyme immobilization and biomaterials separation and purification, etc. Among them, the pH-sensitive, thermosensitive and pH/temperature responsive hydrogels have attracted great interest from both fundamental and application fields at present. Therefore, from the point of view of molecule design, a series of pH-sensitive, thermosensitive and pH/temperature responsive hydrogels were prepared based on the acrylic acid with the excellent pH sensitivity and N-isopropylacrylamide (NIPA) with the excellent temperature sensitivity. Study on the basic physical characteristic, like density, molecular weight, equilibrium water content, crosslink density and fixed charge density etc. measurement of the swelling and deswelling under different ionic strength of the hydrogels were performed, and the mechanism of the response had also been discussed. At last, the mechanical properties of the three kinds of hydrogel were measured. The main results obtained are as follows:1. As to the pH sensitive hydrogel, the ionic strength affects its swelling ratio greatly, the swelling ratio decreases with the salinity rises;the mechanical properties of the pH sensitive hydrogel varies with pH value, when the pH is less than six, the hydrogel shrinks, and its mechanical feature is better than the swollen state which induced by the high pH value (when pH value is over six)2. As to the hydrogel responsible to temperature, the ionic strength is the key factor which has much influence on the swelling ratio, the influence way is the same with the pH sensitive hydrogel, the swelling ratio decreases with the ionic strength rises;used acrylamide copolymerized with N-isopropylacrylamide, which increases the lower critical solution temperature (LCST) to 45°C, as published the LCST is about 32°C;temperature also has great influence on the mechanical properties of thermo sensitive hydrogel, when the temperature reaches its LCST, Young's modulus of hydrogel improve much, for example, the sample in 0.2 M aqueous solution, its Young's modulus could improve 44 percent.3. As to the pH/temperature responsive hydrogel, the pH and temperature are the basic parameters that affect the equilibrium swelling ratio. Under the same lower pH value, the swelling ratio decreases with temperature rises;and the ionic strength greatly affects the swelling of the pH temperature responsive hydrogel, because the ion shielding effect exists, the higher the ion concentration is, the lower the swelling ratio is.