PNIPA纳米复合水凝胶的制备与表征
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摘要
温敏性聚N-异丙基丙烯酰胺(PNIPA)高分子水凝胶由于具有良好的弹性和可塑性、高吸水性以及易加工、低污染等优点,并且最低临界溶液温度(LCST)接近人体生理学温度,被广泛应用于生物技术、环境工程等领域。然而机械强度不高、平衡溶胀率较低等不足之处限制了其应用范围。研究表明,在聚合物水凝胶网络中添加功能化的纳米粒子制备成温敏性纳米复合水凝胶,可使水凝胶的强度、稳定性、溶胀吸水等性能有所改变,从而可应用于更多的领域。
本文分别将亲水改性后的石墨烯颗粒和纳米Si02粒子添加到PNIPA水凝胶网络中制备出PNIPA纳米复合水凝胶,并通过改变纳米粒子添加量研究其对复合凝胶体系性能的影响。
石墨烯是一种由完美的碳六元环按二维蜂窝状紧密堆叠成网状晶格结构并拥有较大比表面积和优异的力学、电学等性能的新型碳质材料。利用FTIR﹑Raman﹑FE-SEM等方法对PNIPA/石墨烯纳米复合水凝胶的结构和形貌进行了表征。结果发现石墨烯以片层形态比较均匀的分散于复合体系网络中,使复合体系干凝胶表面结构中出现大量褶皱,致密程度下降。随着石墨烯含量的增加,复合凝胶的溶胀率降低,而平衡溶胀率增大,并且提高了最终保水率。凝胶行为测试结果显示,复合体系的储能模量G’远大于损耗模量G”,且随着石墨烯含量增大,G'平衡值最高达3500Pa,说明复合体系已形成了完整的三维网络凝胶。通过对凝胶点的测试发现石墨烯的引入并没有显著影响复合体系的LCST,仍在350C附近,这说明了PNIPA的分子结构没有发生本质变化,也间接表明石墨烯粒子是以物理共混分散在PNIPA凝胶中,二者之间没有产生较多的化学键合作用。有趣的是,湿凝胶的Raman光谱上出现了CO2的强吸收峰,表明复合凝胶体系对CO2有较强的吸附能力。
硅溶胶为纳米级的SiO2颗粒在水中或溶剂中的分散液,SiO2颗粒表面含有大量羟基。PNIPA/SiO2复合体系的FTIR与SEM测试结果表明,纳米Si02粒子分散于凝胶网络结构中或吸附在高分子链段周围,与聚合物之间存在一定的相互作用,使复合体系网孔扩张,交联度降低。随着纳米Si02的增多,凝胶的溶胀吸水、力学强度等性能有所改变。特别是纳米Si02含量为5wt%时,不仅复合凝胶对水的释放速率基本趋于恒定,其复合体系破坏所能承受的压强高达47.2KPa,而且储能模量G’平衡值增大至3300Pa。凝胶行为测试结果显示纳米SiO2的引入并没有显著影响复合体系的LCST,这也表明纳米SiO2的引入并未改变聚合物的分子结构。
纳米SiO2粒子和亲水改性石墨烯的引入,不但能综合纳米粒子和PNIPA水凝胶材料的优点,还能从某些角度使PNIPA水凝胶本身的溶胀、吸水、强度等性能有所改变,从而应用于特定的领域。纳米SiO2具有较高的表面活性,可与PNIPA大分子链上的酰胺基团或氢键等相互作用,产生物理交联,当纳米SiO2含量高时,还可适当阻碍聚合物的化学交联,而且凝胶网络的阻隔效应可使纳米SiO2粒子在凝胶中稳定存在,改变凝胶的力学、热学等性能,为拓宽温敏性智能高分子水凝胶的实际应用范围奠定了基础。另外,凝胶的网络结构可支撑石墨烯的三维结构,并可通过聚合物链段阻碍石墨烯的重叠团聚,使石墨烯微片以真正的纳米形态分散在聚合物中,充分发挥其比表面积大的优势,从而使石墨烯材料在一些领域上实现应用的可能性。
PNIPA hygrogels has been widely used in biological technology, environmental engineering, and other fields due to its good elasticity and plasticity, high water imbibition, low pollution and other advantages, especially its LCST close to human physiology temperature. However, the lower mechanical strength and balance swelling rate limit its application scope. The research indicates that adding functional nanoparticles into PNIPA network can make some of the performances of the nanocomposite hydrogels changed.
In this paper, graphene and nano SiO2particles were respectively added into PNIPA gels, preparing PNIPA/Graphene and PNIPA/SiO2nanocomposite hydrogels. The effects of the content of nanoparticles on the performance of the system were studied.
Graphene is a kind of new carbon material with the perfect two dimensional structure, which has bigger specific surface area and excellent mechanical and electrical properties. The structure and morphology of the PNIPA/Graphene nanocomposite hydrogels were characterized by FTIR, Raman and FE-SEM. The results indicated that graphene layer was scattered evenly in the system of network, making its density degree of surface structure get down and a large amount of drape appear. The SR of composite gels reduced and the ESR increased with the increase of the content of graphene, the final water retention of the composite gels also improved. The results of the test for gel behavior showed that G'of the composite system was far higher than G'', and with the content of graphene increased, G'was up to3500Pa. In addition, the gel point testing indicated that the mixed graphene had no obvious effects on the LCST of composite system, which was still near35℃. It showed that no more chemical bonds occurred between graphene and PNIPA hydrogels. In addition, characteristic peak of CO2appeared in Raman spectrum, which indicated that the composite system has strong adsorption ability for CO2.
The surface of SiO2particle contains a lot of hydroxyl. The results of FTIR and SEM of PNIPA/SiO composite system showed that nano SiO2particles were either dispersed evenly in the network or adsorbed on the chains of polymer. The interaction between the polymer network and nano SiO2particles made the mesh on the surface of composite gels expand and the crosslinking degree decreased. With the increasing of the nano SiO2, some of the performances of the composite system were changed. Especially when the nano SiO2content was up to5wt%, the release of water performance was greatly improved, the pressure that the composite system can withstand when it was damaged was as high as47.2KPa, and storage modulus G'was increased to3300Pa. In addition, the results of the test for gel behavior showed that the doped nano SiO2had no significant effects of the LCST of composite hydrogels, which indicated that the polymer structure had no change.
PNIPA nanocomposite hydrogels not only maintained the original excellent performances, but also changed the comprehensive performance due to the introduction of the nanoparticles under some certain fields, such as swelling and strength properties. Nano SiO has high surface activity, and can produce interaction with PNIPA macromolecular chain groups or hydrogen bonding. When the content of nano SiO2increased, it can also block chemical crosslinking of gels, which changed some performances of gels and laid a foundation for widening application fields of intelligent polymer hydrogels. In addition, the network structure can support the three dimensional structure of graphene, and through the polymer chains block overlap or agglomeration of graphene, making the graphite surfaces dispersed in polymers by nano morphology and giving full play to its specific surface area of the advantages, so that the possibility of application of the graphite surfaces in some areas may be realized.
本文分别将亲水改性后的石墨烯颗粒和纳米Si02粒子添加到PNIPA水凝胶网络中制备出PNIPA纳米复合水凝胶,并通过改变纳米粒子添加量研究其对复合凝胶体系性能的影响。
石墨烯是一种由完美的碳六元环按二维蜂窝状紧密堆叠成网状晶格结构并拥有较大比表面积和优异的力学、电学等性能的新型碳质材料。利用FTIR﹑Raman﹑FE-SEM等方法对PNIPA/石墨烯纳米复合水凝胶的结构和形貌进行了表征。结果发现石墨烯以片层形态比较均匀的分散于复合体系网络中,使复合体系干凝胶表面结构中出现大量褶皱,致密程度下降。随着石墨烯含量的增加,复合凝胶的溶胀率降低,而平衡溶胀率增大,并且提高了最终保水率。凝胶行为测试结果显示,复合体系的储能模量G’远大于损耗模量G”,且随着石墨烯含量增大,G'平衡值最高达3500Pa,说明复合体系已形成了完整的三维网络凝胶。通过对凝胶点的测试发现石墨烯的引入并没有显著影响复合体系的LCST,仍在350C附近,这说明了PNIPA的分子结构没有发生本质变化,也间接表明石墨烯粒子是以物理共混分散在PNIPA凝胶中,二者之间没有产生较多的化学键合作用。有趣的是,湿凝胶的Raman光谱上出现了CO2的强吸收峰,表明复合凝胶体系对CO2有较强的吸附能力。
硅溶胶为纳米级的SiO2颗粒在水中或溶剂中的分散液,SiO2颗粒表面含有大量羟基。PNIPA/SiO2复合体系的FTIR与SEM测试结果表明,纳米Si02粒子分散于凝胶网络结构中或吸附在高分子链段周围,与聚合物之间存在一定的相互作用,使复合体系网孔扩张,交联度降低。随着纳米Si02的增多,凝胶的溶胀吸水、力学强度等性能有所改变。特别是纳米Si02含量为5wt%时,不仅复合凝胶对水的释放速率基本趋于恒定,其复合体系破坏所能承受的压强高达47.2KPa,而且储能模量G’平衡值增大至3300Pa。凝胶行为测试结果显示纳米SiO2的引入并没有显著影响复合体系的LCST,这也表明纳米SiO2的引入并未改变聚合物的分子结构。
纳米SiO2粒子和亲水改性石墨烯的引入,不但能综合纳米粒子和PNIPA水凝胶材料的优点,还能从某些角度使PNIPA水凝胶本身的溶胀、吸水、强度等性能有所改变,从而应用于特定的领域。纳米SiO2具有较高的表面活性,可与PNIPA大分子链上的酰胺基团或氢键等相互作用,产生物理交联,当纳米SiO2含量高时,还可适当阻碍聚合物的化学交联,而且凝胶网络的阻隔效应可使纳米SiO2粒子在凝胶中稳定存在,改变凝胶的力学、热学等性能,为拓宽温敏性智能高分子水凝胶的实际应用范围奠定了基础。另外,凝胶的网络结构可支撑石墨烯的三维结构,并可通过聚合物链段阻碍石墨烯的重叠团聚,使石墨烯微片以真正的纳米形态分散在聚合物中,充分发挥其比表面积大的优势,从而使石墨烯材料在一些领域上实现应用的可能性。
PNIPA hygrogels has been widely used in biological technology, environmental engineering, and other fields due to its good elasticity and plasticity, high water imbibition, low pollution and other advantages, especially its LCST close to human physiology temperature. However, the lower mechanical strength and balance swelling rate limit its application scope. The research indicates that adding functional nanoparticles into PNIPA network can make some of the performances of the nanocomposite hydrogels changed.
In this paper, graphene and nano SiO2particles were respectively added into PNIPA gels, preparing PNIPA/Graphene and PNIPA/SiO2nanocomposite hydrogels. The effects of the content of nanoparticles on the performance of the system were studied.
Graphene is a kind of new carbon material with the perfect two dimensional structure, which has bigger specific surface area and excellent mechanical and electrical properties. The structure and morphology of the PNIPA/Graphene nanocomposite hydrogels were characterized by FTIR, Raman and FE-SEM. The results indicated that graphene layer was scattered evenly in the system of network, making its density degree of surface structure get down and a large amount of drape appear. The SR of composite gels reduced and the ESR increased with the increase of the content of graphene, the final water retention of the composite gels also improved. The results of the test for gel behavior showed that G'of the composite system was far higher than G'', and with the content of graphene increased, G'was up to3500Pa. In addition, the gel point testing indicated that the mixed graphene had no obvious effects on the LCST of composite system, which was still near35℃. It showed that no more chemical bonds occurred between graphene and PNIPA hydrogels. In addition, characteristic peak of CO2appeared in Raman spectrum, which indicated that the composite system has strong adsorption ability for CO2.
The surface of SiO2particle contains a lot of hydroxyl. The results of FTIR and SEM of PNIPA/SiO composite system showed that nano SiO2particles were either dispersed evenly in the network or adsorbed on the chains of polymer. The interaction between the polymer network and nano SiO2particles made the mesh on the surface of composite gels expand and the crosslinking degree decreased. With the increasing of the nano SiO2, some of the performances of the composite system were changed. Especially when the nano SiO2content was up to5wt%, the release of water performance was greatly improved, the pressure that the composite system can withstand when it was damaged was as high as47.2KPa, and storage modulus G'was increased to3300Pa. In addition, the results of the test for gel behavior showed that the doped nano SiO2had no significant effects of the LCST of composite hydrogels, which indicated that the polymer structure had no change.
PNIPA nanocomposite hydrogels not only maintained the original excellent performances, but also changed the comprehensive performance due to the introduction of the nanoparticles under some certain fields, such as swelling and strength properties. Nano SiO has high surface activity, and can produce interaction with PNIPA macromolecular chain groups or hydrogen bonding. When the content of nano SiO2increased, it can also block chemical crosslinking of gels, which changed some performances of gels and laid a foundation for widening application fields of intelligent polymer hydrogels. In addition, the network structure can support the three dimensional structure of graphene, and through the polymer chains block overlap or agglomeration of graphene, making the graphite surfaces dispersed in polymers by nano morphology and giving full play to its specific surface area of the advantages, so that the possibility of application of the graphite surfaces in some areas may be realized.
引文
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