An inorganic cross-linked quadruple shape memory hydrogel with high mechanical performance

Shape memory hydrogels (SMHs) have been the subject of great interest in recent years. However, there were few reports on the simultaneous multiple shape memory and high mechanical performance. Therefore, a novel nanocomposite (NC) hydrogel poly (acrylic acid)/Chitosan/ Laponite (PAA/CS/Laponite) was developed by using Laponite as physical cross-linker. In order to achieve three temporary shapes, the PAA/CS/Laponite was soaked in iron chloride hexahydrate (FeCl₃), sodium hydroxide (NaCl) and sodium hydroxide (NaOH) respectively to (a) form metal coordination; (b) gain the chains entanglement of chitosan; (c) get the microcrystalline structure of chitosan. The maximum shape fixity ratio of PAA/CS/Laponite can reach 100% in 1 minute and it can be restored its original shape within 5 minutes. Moreover, PAA/CS/Laponite showed excellent mechanical performance. The maximum tensile and compressive strengths were 0.73 MPa and 13.1 MPa. By comparison with PAA/CS obtained from our previous work, the tensile strength, elongation at break and compressive strength increased by 2.21 times, 1.46 times, and 3.26 times respectively. Scanning electron microscopy (SEM) showed that the obtained sample has uniform honeycomb network structures which can effectively explain why the gel has strong mechanical performance. These characteristics make PAA/CS/Laponite have huge application potential in reality.     

CONTROLLING HIGHTEMPERATURE DEFORMATION BY VARYING MICROSTRUCTURE IN A Ti47Al2Cr2Nb ALLOY

１　ＩＮＴＲＯＤＵＣＴＩＯＮγＴｉＡｌａｌｌｏｙｓａｒｅａｔｔｒａｃｔｉｖｅｓｔｒｕｃｔｕｒａｌｍａｔｅｒｉａｌｓｂｅｃａｕｓｅｏｆｔｈｅｉｒｐｏｔｅｎｔｉａｌａｐｐｌｉｃａｔｉｏｎｓｉｎａｅｒｏｓｐａｃｅａｎｄａｕｔｏｍｏｂｉｌｅｉｎｄｕｓｔｒｉｅｓ［１］．ＣｕｒｒｅｎｔｒｅｓｅａｒｃｈｏｎγＴｉＡｌｉｓｐｒｉｍａｒｉｌｙｆｏｃｕｓｅｄｏｎｉｍｐｒｏｖｉｎｇｉｔｓｒｏｏｍｔｅｍｐｅｒａｔｕｒｅｄｕｃｔｉｌｉｔｙ,ｔｏｕｇｈｎｅｓｓａｎｄｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｃｒｅｅｐｒｅ…     

锆对高阻尼Zn—22%Al合金显微组织和力学性能的影响

通过测试自然时效和人工时效的强度－时间关系曲线,以及采用金相显微镜、透射电镜和扫描电镜观察,探讨了微量锆对经８０℃轧制的Ｚｎ２２％Ａｌ合金显微组织和力学性能的影响。结果表明,在低于８０℃的温轧温度下时效时,加０．０８％～０．３２％Ｚｒ和不加Ｚｒ的Ｚｎ２２％Ａｌ合金的强度保持不变。锆具有细化Ｚｎ２２％Ａｌ合金的组织并阻碍时效时晶粒长大和等轴程度降低的作用。锆还可提高Ｚｎ２２％Ａｌ合金的强度和时效时力学性能的稳定性。在三个不同含锆量的Ｚｎ２２％Ａｌ合金中,含０．１８％Ｚｒ的合金强度最高,而且最稳定。     

非离子型凝胶球在水中的溶胀行为

以过硫酸铵和N,N,N',N',-四甲基乙二胺氧化-还原体系引发丙烯酰胺聚合,制备球状非离子型水凝胶.利用带刻度的显微镜记录了凝胶球在水中的溶胀扩散过程,采用Tanaka-Fillmore凝胶溶胀动力学模型进行数学处理,得到凝胶网络扩散系数.在此基础上,进一步考察了交联剂、引发剂、单体浓度对凝胶网络扩散系数的影响,结果表明:随着交联剂用量的提高,扩散系数先变小后增大;增加引发剂﹑单体浓度,扩散系数均增大.对凝胶网络扩散系数-温度理论模型进行修正,更加符合实验结果,可用于凝胶网络扩散系数的预测.     

Thermoreversible hydrogel. V. Synthesis and swelling behavior of the N-isopropylacrylamide-co-trimethyl methacryloyloxyethyl ammonium iodide copolymeric hydrogels

A series of N-isopropylacrylamide/trimethyl methacryloyloxyethyl ammonium iodide (NIPAAm/TMMAI) copolymeric gels are prepared from the various molar ratios of NIPAAm, cationic monomer TMMAI, and N,N′-methylene bisacrylamide (NMBA) in this article. The influences of the amount of the cationic monomer in the copolymeric gels on the swelling behavior in water, various saline solutions, and various temperatures are investigated. Results show that the swelling ratios of copolymeric gels are significantly larger than those of pure homopolymer NIPAAm gel, and the more the TMMAI content, the higher the gel transition temperature. In the saline solution, results show that the swelling ratio of pure NIPAAm gel has not significantly changed with an increase of the salt concentration until the salt concentration is larger than 0.1M. The swelling ratios for the copolymeric gels NIPAAm/TMMAI decrease with increasing salt concentration. In various saline solutions, results show that the anionic effects are greater than cationic effects in the presence of common anion, different cations and common cation, and different anions for these hydrogels. Finally, we also tested the reversibility of the NIPAAm/TMMAI copolymeric gels. The deswelling and reswelling kinetics are dependent on the temperature, which is below or above the gel transition temperature. The gel with little TMMAI content has a good reversibility. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1793–1803, 1998     

Preparation and swelling properties of glycoside-bearing hydrogels by gamma-ray radiation to glycoside-bearing polymer aqueous solutions

γ-Ray radiation on poly(glucosyloxyethyl methacrylate) [poly(GEMA)] and poly(glucosyloxyethyl acrylate) [poly(GEA)] aqueous solutions without any crosslinkers gives glycoside-bearing hydrogels in a high yield. The degree of the swelling ratios of each obtained hydrogel in water was decreased with an increase in the total radiation dose to each polymer solution. In order to clarify the formation mechanism of obtained poly(GEMA) hydrogel by γ-ray radiation, the swelling properties of each hydrogel were also compared with those of poly(GEA) under various conditions. Poly(GEMA) in an organic solvent, N,N-dimethylformamide and dimethylsulfoxide, was not gelled by γ-ray radiation, although poly(GEA) was gelled under these conditions. These results suggest that the radiation formation mechanism of the poly(GEMA) hydrogels is different from that of the poly(GEA) hydrogels. In addition, the radiolysis of water is necessary in order to form the hydrogels for poly(GEMA). Next, we predicted the radiation formation mechanism of the poly(GEMA) hydrogels by the crosslinking between the glucoside moieties in poly(GEMA). © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 965–972, 1998     

In Situ Monitoring of Lipid Phase State Make Target Lipid Mixtures Similar to Intercellular Lipid in the Stratum Corneum

In this study, lipid structural change is monitored using Raman spectroscopy during heat treatment, along with the impact of lipid states on the structural and physical properties during the preparation process of the dried and hydrated lipid mixture (LM) similar to intercellular lipid in stratum corneum. The microstructures and thermal behavior of these LMs change depending on the melting of lipid ingredients in the preparation process. It is recognized that variable temperature Raman spectroscopy (VT‐Raman) is a useful and attractive tool for the sensitive in situ monitoring of lipid state changes and lipid melting. The LMs can incorporate D₂O into their structures regardless of preparation temperature due to increasing lattice distance by hydration. These results suggest that monitoring lipid structural changes during the heating step is important to precisely prepare target LMs. Practical Applications: This study reveals that VT‐Raman is a useful and attractive tool in in situ monitoring of lipid state change and lipid melting. The monitoring of the preparation process by VT‐Raman is necessary to precisely prepare the target LM similar to intercellular lipid of stratum corneum because the microstructures and thermal properties of these LMs change depending on the melting of lipid ingredients during the preparation process.     

Fabrication of Photothermally Responsive Nanocomposite Hydrogel through 3D Printing

The responsive hydrogels have received great attention in many fields. However, the molding method and response mode of such hydrogels are criticized when it comes to real applications. In this work, a novel class of poly(N‐isopropyl acrylamide)/graphene oxide (PNIPAm/GO) nanocomposite hydrogel through self‐assembly three‐dimensional (3D) printing via ultraviolet light polymerization. The precursor is ordinarily constituted by NIPAm monomer, crosslinker, and water mixed with a photoinitiator, besides the introduction of nanoclay adjusts the shear thinning properties to an optimal level, which is important for the 3D printing precision. Then, the graphite oxide as infrared light absorber endows the hydrogel fast photothermal excited responsivity instead of conventional temperature response. The shrinkage and swelling of the composite hydrogel can be controlled by turning the near‐infrared light on or off. Meanwhile, the reversible behavior of as‐prepared hydrogel is easily regulated by altering the content of GO and illumination time of near‐infrared light. Additionally, a round tube is obtained based on the as‐prepared hydrogel, which can be driven to get a pencil, indicating their potential applications in actuator and other functional program.     

壳聚糖接枝PAAm半互穿网络凝胶的性能

以过硫酸钾(KPS)为自由基引发剂,在壳聚糖(CS)上接枝共聚了聚丙烯酰胺(PAAm).以亚甲基双丙烯酰胺(MBA)或甲醛为交联剂,并研究了试验因素,如交联剂浓度和单体比率对水凝胶溶胀能力的影响.试验表明水凝胶具有离子强度敏感性、pH敏感性和温度敏感性.这种可随外界因素响应及"开关"的性质,使此类智能水凝胶有望成为生物制品载体,例如药物载体.