具有双网络结构高强度和形状记忆水凝胶（英文）

本文将形状记忆功能引入到双网络水凝胶设计之中.首先合成了聚乙二醇-聚丙烯酰氧乙基三甲基氯化铵/聚(丙烯酰胺-co-丙烯酸)(PEG-PDAC/P(AAm-co-AAc))双网络水凝胶,其中第一套网络由交联的聚乙二醇(PEG)链组成,包埋着聚电解质聚丙烯酰氧乙基三甲基氯化铵(PDAC);第二套网络由丙烯酰胺(AAm)和丙烯酸(AAc)的共聚物交联组成,交联剂为N,N'-亚甲基双丙烯酰胺(MBAA).结果表明,双网络水凝胶显示出高强度的特点,其断裂应力和韧性分别达到了0.9 MPa和3.8 MJ/m~3.和传统地利用中性高分子作为柔软和韧性的第二套网络相比较,本文选择将具有弱电解质特性的丙烯酸单体引入到第二套网络中,利用丙烯酸与三价铁离子的络合作用,成功地赋予水凝胶在氧化环氧反应条件下的形状记忆功能.结果表明,只要巧妙地引入响应性单体,高强度和形状记忆这两种最重要的特性可以同时被引入到双网络水凝胶的设计之中.     

基于离子特异性效应调控聚电解质络合物水凝胶自修复性能

通过两步聚合法制备了甲基丙烯酰胺丙基三甲基氯化铵（MPTC）和苯乙烯磺酸钠（NaSS）聚电解质络合物（PMPTC/PNaSS）水凝胶,研究了基于离子特异性效应调控聚电解质络合物水凝胶的自修复性能.通过不同种类离子对PMPTC/PNaSS水凝胶的特异性掺杂,可影响水凝胶中聚电解质链间静电相互作用以及链的运动能力,从而控制水凝胶的力学性能以及自修复性能.结果表明,当掺杂阴离子从结构构造型的强水化离子变为结构破坏型的弱水化离子,聚电解质络合物水凝胶的自修复效率会逐渐增加.主要是由于结构破坏型阴离子可以更加有效地打开水凝胶中的离子键,提高聚电解质链的运动能力和自修复效率.     

聚丙烯酰胺衍生物凝胶体系的合成与光谱表征

采用聚丙烯酰胺直接氮烷基化的方法,在PAM的侧链上引入了烯丙基,通过自由基引发交联并水解,合成了聚丙烯酰胺自由基交联的弱凝胶,并研究了其结构、凝胶形成过程以及NaCl浓度对凝胶表观粘度的影响。结果表明：交联比的改变,对交联时间、破胶时间和凝胶强度均有影响,随着交联比的增大,交联时间减少,凝胶强度略有增大;聚丙烯酰胺衍生物交联体系的表观粘度随着NaCl质量浓度的增加而增加,具有良好的抗盐性能。     

多溶剂响应自折叠水凝胶

本文基于寡聚乙二醇甲醚甲基丙烯酸酯(OEGMA)和2-甲基-2-丙烯酸-2-(2-甲氧基乙氧基)乙酯(MEO₂MA)设计了一种自折叠水凝胶. 在室温下,P(MEO₂MA-co-OEGMA)凝胶能够在多种溶剂中自折叠形成三维结构. 凝胶不均匀膨胀导致内应力增强,从而使得片状凝胶可以在三维结构和二维形状之间进行可逆转换. 研究表明,凝胶组成、固化气体环境和成型过程对水凝胶的自折叠过程起着重要的影响.     

Mg2+掺杂Zn2SiO4:Mn2+的溶胶-凝胶法合成及真空紫外发光特性研究

采用溶胶-凝胶法（sol-gel method）于不同气氛条件下成功合成了Zn_1.92-xMg_xSiO₄:0.08Mn²⁺（0≤x≤0.12）系列粉末样品.利用X射线衍射(XRD)、光致发光(PL)谱等分析手段对Zn_1.92-xMg_xSiO₄:0.08Mn²⁺系列     

离子液体凝胶聚合物电解质PP13TFSI-LiTFSI-P(VdF-HFP)的电化学性能 (cited: 1)

采用溶液浇铸法将N-甲基-N-丙基哌啶二(三氟甲基磺)亚胺(PP13TFSI)、二(三氟甲基磺)亚胺锂与偏氟乙烯-六氟丙烯共聚物(P(VdF-HFP))混合制备离子液体凝胶聚合物电解质(ILGPEs). 通过扫描电子显微镜观察发现,这种离子液体凝胶聚合物电解质由于液体相的均匀分布而具有疏松的结构. 采用电化学阻抗、计时电流法、线性扫描伏安法测试了电解质的离子电导率、锂离子迁移数和电化学窗口. 室温下离子液体凝胶聚合物电解质的离子电导率和锂离子迁移数分别是0.79 mS/cm和0.71,电化学窗口为0～5.1 Vvs. Li⁺/Li. 电池性能测试表明,这种离子液体凝胶聚合物电解质在Li/LiFePO₄电池中是稳定的,放电容量在30、75和150mA/g倍率下分别为135、117和100 mAh/g,电池经100个循环后容量保持在100%而几乎没有衰减.     

燃料电池系统最大热力学电效率及对氢气、甲烷和丙烷的应用结果

燃料电池系统的最大电效率（η_e^max）对理解和发展燃料电池技术至关重要.本文通过对燃料电池系统的热力学分析,在考虑加热燃料与空气至燃料电池工作温度的热量需求的基础上,建立了燃料电池运行过程的能量平衡关系,进而推导出了η_e^max的显式理论表达式.结果表明,与卡诺效率不同,η_e^max与燃料有关.由于除氢燃料外,计算η_e^max需要进行化学平衡计算,本文推导了烷烃燃料化学平衡态的解析解.所得理论模型被用于分析温度（T）与燃料水含量及废热回收率对η_e^max的影响.结果表明,甲烷和丙烷燃料的η_e^max随温度的升高而显著降低.此外,对中等废热回收率且运行于700 ℃≤T≤900 ℃的燃料电池系统,氢气燃料的η_e^max要高于甲烷和丙烷燃料的η_e^max.     

壳聚糖水凝胶折射率特性研究

水凝胶是一种具有三维网络结构的新型功能高分子材料。水凝胶因其可注射性、良好的组织相容性、无毒副作用、在生物体内可降解性、环境敏感性广泛用于药物释控、吸附材料、仿生工程、光纤传感、组织工程、智能穿戴等方面。水凝胶的传感主要是随着外界环境因素的改变,引起溶胀度的不同,导致水分子填补凝胶内部孔洞的程度不同,呈现出水凝胶整体折射率变化的过程。为了研究不同的溶胀度对水凝胶折射率的影响,以壳聚糖为原料,以过硫酸铵, N,N-亚甲基双丙烯酰胺分别作为引发剂和交联剂,与丙烯酸接枝反应,在氮气的环境中以化学方式制备壳聚糖水凝胶。通过设计测量结构、搭建实验平台,检测了壳聚糖水凝胶的溶胀特性并对凝胶的溶胀度进行了标定;以卤钨灯作为光源,通过光谱仪检测了壳聚糖水凝胶透射光谱;运用光在介质面传播特性与光波的偏振性原理,对壳聚糖水凝胶透射光谱进行分析,研究了不同溶胀度下壳聚糖水凝胶折射率的变化规律,发现了不同溶胀度下凝胶对不同波长光波的折射能力存在差异性;通过对数据的处理,计算了波长为400 nm时,凝胶折射率随溶胀度变化的范围及灵敏度Q_1。通过对实验数据的拟合,得出了壳聚糖水凝胶折射率对溶胀度、波长的响应规律且拟合度较高,为壳聚糖水凝胶在光学传感方面的应用提供了实验基础。通过实验,说明了壳聚糖水凝胶有着优秀的溶胀特性、较宽的折射率变化范围及较高的灵敏度,在智能穿戴、仿真皮肤、光学传感等领域的应用有一定的优势。     

纳米YPO4:Eu3+的合成及发光性质研究

采用水热法合成了纳米Y_1-xPO₄:xEu³⁺（005≤x≤030）系列荧光粉,并对样品进行了热处理.通过X射线衍射（XRD）、扫描电镜（SEM）等手段分析了合成样品的结构及形貌,结果表明合成的样品均为四方磷钇矿结构,在酸性和碱性条件下分别为球状和细棒状,且均在纳米尺度.研究其在真空紫外（VUV）激发下的发光性质发现,样品的激发峰最大值位于142 nm左右;与固相法的样品相比,PO^3-     

Co掺杂对铁磁金属La0.8Sr0.2MnO3磁电阻影响机理

通过对La_0.8Sr_0.2Mn_1-yCo_yO₃(y≤02)饱和磁矩和输运的测量,研究了Co对La_0.8Sr_0.2MnO₃的磁电阻影响机制.结果表明,在La_0.8Sr_0.2Mn_1-yCo_yO₃（y≤02）中Co³⁺离子是低自旋态.由于Mn³⁺—O—Co³⁺—O—Mn³⁺类型的磁交换与Mn³⁺-Mn⁴⁺离子间双交换作用相比较弱,Curie温度T_C附近的磁电阻随着Co掺杂量的增加而降低.与此相反,由于Co²⁺离子与e_g巡游电子的反铁磁交换耦合作用,低温区间的磁电阻随着Co掺杂量的增加而升高.     

Synthesis of Novel Double Network Hydrogels via Atom Transfer Radical Polymerization

Novel double network (DN) hydrogels were prepared via atom transfer radical polymerization (ATRP) of the first network using two different initiators, and followed by ultraviolet (UV) photo-initiated polymerization for the second network. The first networks of DN hydrogels were prepared by using two different initiators; one is a one-side initiator, and the other is a double-side initiator. The mechanical properties of various DN gels, such as water content and compressive strength, were studied. The network structure of the DN hydrogels was also characterized by dynamic light scattering. Thus, we demonstrated that the ATRP method is useful to control the network structure of the first network for DN gels. Extensive inhomogeneous structure of the first network was obtained by ATRP method and increased both the swelling degree and softness of DN gels.     

Preparation and properties of morphology controlled poly(2-hydroxyethyl methacrylate)/poly(N-vinyl pyrrolidone) double networks for biomedical use

Poly(2-hydroxyethyl methacrylate)/poly(N-vinyl pyrrolidone) (PHEMA/PVP) double networks (DN) were prepared using a sequential method by incorporating a second network of crosslinked PVP into PHEMA. We found that the distributions of the two networks can be regulated just by modulating the morphology of the first network, thus giving expected high water content of these gels. Fourier transform infrared (FTIR) spectroscopy and scanning electronic microscopy (SEM) were used to confirm the structure of the DN. The incorporation of more hydrophilic PVP enhanced swelling ability of these gels. Because of improved hydrophilicity, the PHEMA/PVP DN exhibited higher loading capability for water-soluble substance than that of pure PHEMA, while showed a slower release rate than corresponding HEMA/NVP copolymer hydrogel. It is suggested that the DN gels are potential biomaterials for wound dressing, medical implants and other drug delivery systems.     

P(NIPAM-co-AA)/Clay nanocomposite hydrogels exhibiting high swelling ratio accompanied by excellent mechanical strength

In this paper, a series of P(NIPAM-co-AA)/Clay composite hydrogels (abbreviated as NAC gels) with high swelling ratio and excellent mechanical strength were synthesized and characterized by DMA, SEM, and IR. In NAC gels composed of a unique organic P(NIPAM-co-AA)/inorganic (clay) network, the inorganic clay acts as a multifunctional cross-linker in place of an organic cross-linker as used in the conventional chemically cross-linked hydrogels (abbreviated as OR gels). The NAC gels exhibit excellent swelling ratio, and there was no detectable change in properties on altering the concentration of clay, while the swelling ratio tends to decrease slightly when C _clay increases up to 25 wt%, which was revealed in swelling measurements. IR spectra show that clay has been intercalated by copolymers. Furthermore, results of DMA reveal that the composite hydrogel has an excellent mechanical strength by using a wide range of clay concentration, while the moduli improve with increasing C _clay.     

Chemical semi-IPN hydrogels for the removal of adhesives from canvas paintings

Semi-interpenetrating (IPN) poly (2-hydroxyethyl methacrylate)/polyvinylpyrrolidone hydrogels were synthesized and used for the removal of adhesives from the back of canvas paintings. The high water retention capability and the specific mechanical properties of these gels allow the safe cleaning of water-sensitive artifacts using water-based detergent systems. The cleaning action is limited to the contact area and layer-by-layer removal is achieved while avoiding water spreading and absorption within water-sensitive substrates, which could lead, for example, to paint detachment. The use of these chemical gels also avoids leaving residues over the treated surface because the gel network is formed by covalent bonds that provide high mechanical strength. In this contribution, the physicochemical characterization of semi-IPN chemical hydrogels is reported. The successful application of an o/w microemulsion confined in the hydrogel for the removal of adhesives from linen canvas is also illustrated.     

Synthesis and Properties of Polyacrylamide-Based Conducting Gels with Enhanced Mechanical Strength

A nanocomposite conducting hydrogel, polyacrylamide/MWNT/clay (abbreviated as PAM/MWNT/clay), prepared through in situ free radical aqueous polymerization and crosslinked by both clay, as a functional physical crosslinker, and N,N′-methylenebisacrylamide (MBA) as a chemical crosslinker, is reported. The morphology of the gels was characterized by scanning electron microscopy (SEM). The mechanical properties and electrical conductivity were also studied. The results show that the prepared hydrogels had the expected chemical components, with a highly porous structure, and the gels also showed high mechanical strength. The mechanical strength and electrical conductivity value increased with increasing content of multi-walled nanotube (MWNT), and decreased with increasing content of water.     

Study on the Dynamic Rheometry and Swelling Properties of the Polyacrylamide/Laponite Nanocomposite Hydrogels in Electrolyte Media

Polyacrylamide/laponite/chromium triacetate nanocomposite (NC) hydrogels were prepared by incorporation of the laponite nanoparticles in partially hydrolyzed polyacrylamide followed by cross-linking of their aqueous solutions with chromium triacetate. Influence of nanoparticle, cross-linker, polymer concentrations, and gelation media (water) temperature, salinity, and rheometer frequency on the viscoelastic behavior of the NC hydrogels were studied by probing the network properties. In addition, swelling behaviors of these NC gels in tap and oil reservoir water were evaluated. According to dynamic rheometry of the gelation process, the limiting storage modulus of the NC gels increased with increasing laponite content. The addition of laponite into the polyacrylamide gelling system increased their viscous properties more strongly than the elastic properties. The ultimate elastic modulus of the NC gels increased with increasing water salinity and temperature. Increasing rheometer frequency during gelation retarded the sol–gel transition and decreased the ultimate elastic modulus. The equilibrium swelling ratio of the NC hydrogels in tap water decreased with increasing laponite content. The salt sensitivity of the NC gels in oil reservoir water slightly decreased with increasing laponite content. These results suggest the superiority of the hydrolyzed polyacrylamide (HPAM)/chromium acetate/laponite NC hydrogels for water shut-off applications in oil reservoirs as compared with unfilled HPAM gels.     

Tuning of Lower Critical Solution Temperature (LCST) of Poly(N-Isopropylacrylamide-co-Acrylic acid) Hydrogels

Temperature-responsive hydrogel with a lower critical solution temperature (LCST) close to human body temperature was prepared. Crosslinked N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc) copolymer networks were synthesized at various monomer ratios in the presence of ammonium persulfate (APS), N,N′-methylenebisacrylamide (NMBA) and N,N,N′,N′-tetramethylethylenediamine (TEMED) via a redox polymerization method. The resulting hydrogels possessed thermo- and pH-responsive characteristics. They were characterized in terms of swelling ratio, volume change, water uptake and diffusivity, water vapor uptake and diffusivity, and phase transition temperature. The water liquid and vapor diffusion coefficients for all the synthesized hydrogels were higher than the literature data, implying higher rates for drug release. The LCST of the hydrogel increased with higher AAc content in the copolymer. The gel containing 1.8% AAc exhibited an LCST similar to human body temperature, demonstrating a potential use in drug controlled release and biomedical applications.     

Preparation and Property of Poly(N-isopropylacrylamide) (PNIPAAm)/Clay/Linear Polyacrylamide (PAAm) Nanocomposite Hydrogels

In this study, a linear polyacrylamide (PAAm) with an average viscosimetric molecular weight 3.97 × 10³ kg mol^?1 was added to the prereaction solution for the preparation of poly(N-isopropylacrylamide) (PNIPAAm)/clay nanocomposite hydrogels. The effects of the linear PAAm on the optical transparency and tensile property of the resulting PNIPAAm/clay/linear PAAm hydrogels were systematically investigated. The results revealed that the optical transparency and mechanical tensile properties of the resultant hydrogels strongly depended on the linear PAAm content. In particular, 5 wt% loading of linear PAAm led to almost fivefold decreases of transmittance at 25°C and a onefold increase of the tensile elongation at break. These characteristic changes were explained by a typical interpenetrating microstructure, which was formed by PNIPAAm due to the incorporation of linear PAAm in the PNIPAAm/clay network. The dynamic rheological test and infrared spectroscopy analysis on the mixed solutions consisting of linear PAAm and clay platelets further confirmed the interaction.     

Proton-conducting composite membranes derived from poly(2,6-dimethyl-1, 4-phenylene oxide) doped with phosphosilicate gels

Proton-conducting composite membranes were prepared by doping phosphosilicate gels into SPPO polymer matrix. The structure of gels was examined by ³¹P MAS-NMR. The composite membranes were characterized in terms of TGA, mechanical property, water uptake and conductivity. It was found that the composite membranes were thermally stable up to 150 °C, and possessed higher mechanical strength than Nafion112, either in dry state or in wet state. The conductivity of composite membranes increased with the increase of the ion exchange capacity (IEC), relative humidity (R.H.) and doping amounts. The water uptakes of composite membranes are much higher than Nafion112 in weight percent form at room temperature, and the highest conductivity value of 0.216 S cm^− 1 was achieved for water equilibrated membranes, 2.5 times higher than 0.0871 S·cm^− 1 for Nafion112 measured under the same condition. It is suggested that the composite membranes should be the promising candidates used in PEMFC.     

Influence of environmental solution pH and microstructural parameters on mechanical behavior of amphoteric pH-sensitive hydrogels

Amphoteric hydrogels contain both ionizable acidic and basic groups attached on the polymer chains, which can change their volume in response to the slight alteration of the surrounding environmental p H. In this paper, a theory of equilibrium swelling of amphoteric p H-sensitive hydrogels which is an extension of the formalism proposed by Marcombe et al. and a new hybrid free-energy density function of amphoteric hydrogels composed of the Edwards-Vilgis slip-link model and the Flory-Huggins solution theory as well as the contributions of mixing the mobile ions with the solvent, and dissociating the acidic and basic groups are presented for the prediction of the influence of environmental solution p H, microstructural parameters and geometric constraints on mechanical behavior. The calculations were modeled on chitosan-genipin gels, and the results were compared to experimental data. Numerical calculations show that the model is able to predict the dependence of swelling on p H and crosslinker qualitatively well and quantitatively close to the experimental data. Each gel shows minimal swelling at low p H but an increase in swelling until a maximum was reached; for most of the p H range, a good fit was achieved except for where the maximum swelling occurs; for experimental data, the maximum swelling appears at about pH = 4 , but for modeled data the maximum swelling appears between pH = 4 and pH = 6 ; each gel swell decreasing with increasing crosslinker concentration was also successfully predicted. The calculated results also show that microstructural parameters and geometric constraints have a significant impact on the mechanical behavior of the amphoteric hydrogels; the gel swells less when the network is more densely entangled and the maximum swelling ratio of the gels under biaxial constraint is only about one-third of the maximum when the gels swell freely. The theory developed here is valuable for the design and optimization of a drug delivery system.