Synthesise And Property Research Of Ph-sensitive Poly(2-(acryloyloxy) Propanoic Acid) Hydrogels

In this paper we synthesized a pH-responsive polymer, mainly discussed its pH sensitivity, application in drug release and different states of water in its hydrogels.The article have three sections, the main contents are listed as follow:Chapter I: The definition, characteristics, response mechanism of biodegradable materials, sensitive polymers and intelligent hydrogel were introduced in detail. At the same time we fouced on preseatation of the advance in the synthesis of pH-responsive polymer and its application in biological engineering field and so on.Chapter II: We used lactic acid as raw material to synthesize functional monomer 2-(acrylic acid) propionic acid by acylation reaction. The monomer structure was characterized by nuclear magnetic resonance spectroscopy (1H-NMR) and infrared spectroscopy (FTIR). With N, N'-methylene bisacrylamide (NMBA) as a cross-linking agent, we prepared pH-sensitive polymer hydrogel, The pH value and temperature dependence of the swelling degree of the hydrogel with different cross-linking agent were examined, as well as inorganic ions on the gel swelling behavior. The further studies of the drug release behavior in different media (deionized water, PBS buffer solution) were made. The results showed that: the hydrogel has a certain response on temperature; the swelling degree of the hydrogel decreases with the increase of salt concentration, especially in the range of low concentration; it has a good response on pH, especially in the range of pH value 4-7 (from acidic to neutral). The cumulative drug release rate and release rate of loaded drug in polymer hydrogel increase with the rise of temperature, and decrease with the increase of crosslinker content; increase significantly with the rise of pH value, which shows the sensitive pH value control release. Those above mentioned results indicat that the hydrogel has a good prospect as a pH sensitive drug delivery system.Chapter III: The pH-sensitive polymer hydrogels were prepared, the states of water in the hydrogel were studied by differential scanning calorimetry (DSC). The existent form and relative conten of the water in the hydrogel had obvious dependence on pH values, different swelling time, and the concentration of different inorganic salt solution. It proves that three different states of water exist in the hydrogel: free water, freezing water and non-freezing water. The results show that: the relative content of the freezing water in the hydrogel increases with the rise of pH value and swelling time; the order of water into the gel network is non-freezing bound water, freezing bound water and freezing free water. The conclusion strengthens our understanding on the microstructure and properties of the hydrogel and provids a certain theoretical reference on the further applications of hydrogel in drug release.