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Structure and Properties of Hydrophobic Aggregation Hydrogel with Chemical Sensitive Switch 时间:2017-10-09 22:28 来源:未知作者:admin 点击: 次 Abstract:Hydrogels with chemical sensitive switch have control release properties in special environments. A series of polyacrylamide-octadecyl methacrylate hydrogels crosslinked by N,N′-bis (acryloyl) cystamine were synthesized as potential chemical sensitive system. When this hydrogel encounters dithiothreitol it can change its quality. The properties of the hydrogels were characterized by infrared spectroscopy, contact angle, and scanning electron microscopy. The water absorption of the hydrogel has the maximum value of 475%, when the content of octadecyl methacrylate is 5 wt%. The amount of weight loss was changed from 34.6% to 17.2%, as the content of octadecyl methacrylate increased from 3 wt% to 9.4 wt%. At the same time, the stress of the hydrogel decreased from 67.01% to 47.61%; the strength of the hydrogel reaches to the maximum 0.367 Mpa at 7 wt% octadecyl methacrylate. The increasing content of octadecyl methacrylate from 3 wt% to 9.4 wt% can enhance the hydrophobicity of the hydrogel; the contact angle of water to hydrogel changed from 14.10° to 19.62°. This hydrogel has the porous structure which permits loading of oils into the gel matrix. The functionalities of the hydrogel make it have more widely potential applications in chemical sensitive response materials.
1. Introduction
Hydrogels usually are prepared by hydrophilic polymers with highly swollen properties, as well as crosslinked three-dimensional structures. Recently studies have been done on hydrogels with mechanical properties and superporous, self-healing, self-assembling, and stimuli-sensitive hydrogels [1–3]. They can be used as wound dressings and in tissue engineering, drug delivery systems, and water treatment agents [4–8].
Stimuli-sensitive hydrogels have become the subject of extensive studies as intelligent materials, because of their multifunctionality in different environments, such as pH, temperature, ultrasound, electric fields, and chemical reagents [9–13]. When these hydrogels are placed in these environments, they change their structure by themselves. Accordingly stimuli-sensitive hydrogels have potential applications in drug carriers by determining the selected solute, removing toxins, recycling, and separating products related to the industrial process.
The problems relating to the smart control of hydrogels were highly concerned [14]. Hydrophobic aggregate is critical to improving the mechanical properties of hydrogels by stress dissipation mechanisms. Aqueous polymer with hydrophobic segments can aggregate at aqueous environment and can be transformed into hydrogels. And disulfide bonds can be designed as a reversible switch in hydrogel design [15]. Therefore, by combining hydrophobic segments with the reversible switch systems, the intelligent hydrogel with sense of chemical changes can be applied in a wide range of applications. As a result, it enables us to make smart systems in separation of specific substances and drug control delivery systems.
Here we reported a chemical sensitive hydrogel and how it responds to dithiothreitol (DTT) in water solution. This material was made by grafting the octadecyl methacrylate and disulfide bond to the PAM. Therefore DTT triggered a quality change owing to breaking the crosslinked S-S bond, and the hydrogel showed the sense of chemical changes properties because of octadecyl methacrylate. The properties of the hydrogel were characterized by mechanic strength and contact angle of water measurements.