Macromolecular nature of nanosheets of quasi‐TiO2 from (tetra‐isopropyl)orthotitanate modified by methacrylic acid

In this paper we concentrate on the general behavior of oxotitanium hydrosol, which was earlier developed by us as a precursor of the TiO₂ nanoparticles and nanocomposite. The oxotitanium hydrosol was synthesized by the chemical decomposition of a molecular complex of the methacrylic acid/(tetra‐isopropyl)orthotitanate (MAA/TIPT) by means of the hydrogen peroxide. The raw product chemical decomposition of MAA/TIPT is the colloidal suspension of the oxotitanium compound in the water. The oxotitanium compound was separated from hydrosol and identified on the basis of X‐ray and Raman spectroscopy investigations. The status of water in the hydrosol was also investigated by the Raman spectroscopy. The photophysical behaviors of the oxotitanium hydrosol on the basis of the light absorption and photoluminescence (PL) investigations are presented. The light absorption (260 nm) and PL emission (313 nm) allow us to identify the inorganic phase of hydrosol as nanosheets' crystallites of quasi‐TiO₂. Macromolecular nature of nanosheets of quasi‐TiO₂ was revealed only for a higher concentration solution of nanosheets' crystallites of quasi‐TiO₂ at the hydrosol. A macromolecular nature of nanosheets of quasi‐TiO₂ by the red shift of absorption edge and PL wavelength with increase in the concentration of the oxotitanium hydrosol as well as the formation of hydrogels and birefringence developed under an influence of mechanical shearing is evidenced. Copyright © 2009 John Wiley & Sons, Ltd.     

The rheology of hydrogels based on chitosan–gelatin (bio)polyelectrolyte complexes

Influence of the chitosan concentration in the low-concentrated acidic hydrogels formed by (bio)polyelectrolyte chitosan–gelatin complexes (at a constant gelatin concentration of 1%) was studied by shearing in steady flow and linear oscillations. These complexes, including native gelatin, demonstrate clearly expressed viscoelastic properties. Viscoelastic properties correlated well with the non-Newtonian behavior of hydrogels (according to the Cox–Merz rule). Increasing the chitosan concentration (from 0.1% to 0.6%) results in exponential growth of the apparent viscosity, yield stress, and storage modulus. However, a further increase in chitosan concentration to 0.8% leads to a reduction in these rheological parameters due to the electrostatic repulsion of similarly charged polyelectrolyte complexes under the high concentration of these complexes. The macro-rheological properties of chitosan–gelatin gels are mainly determined by the colloidal structure of sol-precursors in solutions. The yield stress dependence on the radius of the dispersed particles is of square type. Electron photomicrographs showed that the introduction of even small quantities of chitosan leads to radical changes in the supramolecular structure of the gelatin gel.     

结冷胶与聚乙二醇丙烯酸酯双网络凝胶的制备及生物相容性评价

针对结冷胶脆性较大的问题,将聚乙二醇丙烯酸酯(PEGDA)引入结冷胶,通过紫外交联制备了结冷胶/PEGDA双网络凝胶,并对单组分凝胶和双网络凝胶的溶胀性能、微观形貌、拉伸力学性能、动态压缩性能和流变性能等进行比较.结果表明,双网络凝胶在类生理环境中具有较小的溶胀率和较好的尺寸稳定性,PEGDA的引入能够大幅度提高结冷胶的韧性,双网络凝胶的拉断伸长率可达340%,断裂能达1.01×103J/m2,与天然关节软骨相当.将成纤维细胞种植在凝胶内部进行体外三维立体培养,结果显示,细胞在凝胶内部生存状态良好,双网络凝胶的细胞负载率高于单网络结冷胶,说明该体系在生物医用领域具有良好的应用前景.     

基于β-环糊精接枝聚L-谷氨酸星型聚合物的可注射水凝胶的制备与表征

采用Gadelle-Defaye法制备了全-6-氨基-β-环糊精[β-CD-(NH2)7],并用"Grafting-from"接枝法得到不同分子量的星型结构β-环糊精-g-聚L-谷氨酸(β-CD-g-PLGA).对β-CD-g-PLGA进行酰肼化改性后与醛基化海藻酸钠(ALG-CHO)通过席夫碱交联反应制备β-CD-g-PLGA/ALG水凝胶.研究了前驱体浓度以及β-CD-gPLGA分子量对β-CD-g-PLGA/ALG水凝胶性能的影响,并以疏水性辛伐他汀(SIM)为模型药物,研究了水凝胶对SIM的控制释放行为.     

Study on superabsorbent of maleic anhydride/acrylamide semi‐interpenetrated with poly(vinyl alcohol)

A series of superabsorbents of maleic anhydride (MAH)/acrylamide (AM) interpenetrated with poly(vinyl alcohol) (PVA) were prepared by aqueous polymerization, using N,N‐methylenebiacrylamide (NNMBA) as a crosslinker and ammonium persulfate (APS) as an initiator. The samples were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscope (SEM). The effects of reaction variables on the water absorbency of the superabsorbents in distilled water and in 0.9 wt% NaCl solution were investigated. In addition, the effect of the PVA content on the swelling rate and sensitivity to saline of the superabsorbents were also investigated. The results showed that the absorbency, both in 0.9 wt% NaCl solution and in distilled water, first decreased and then increased with increasing PVA content. Moreover, the resultant superabsorbent had a higher absorption rate and it became less sensitive to saline by incorporating certain amount of PVA into the network of the hydrogel. Copyright © 2009 John Wiley & Sons, Ltd.     

Influence of the nature of the porous confining network on the sorption, diffusion and mechanical properties of hydrogel IPNs

Two series of amphiphilic hydrogels of various compositions were prepared by sequentially interpenetrating two polymer networks, a poly(2-hydroxyethyl acrylate) (PHEA) network inside either a macroporous matrix of poly(methyl methacrylate) (PMMA) or a macroporous poly(ethyl acrylate) (PEA) network. In both cases poly(2-hydroxyethyl acrylate) (PHEA) served as network II, and the firstly formed porous network was a hydrophobic homonetwork, PMMA or PEA, that conferred mechanical strength to the hydrogel. In order to obtain hydrogels with high hydrophilic content, the first network was prepared in the presence of a solvent, thus yielding a macroporous network. The two families of IPNs thus obtained were: (net-PMMA)-ipn-(net-PHEA) and (net-PEA)-ipn-(net-PHEA), with a PHEA content ranging from 36% to 87% and from 64% to 94%, respectively. The novelty of the work consisted in comparing the effect of using as the first macroporous network a polymer which is glassy at room temperature (PMMA) and another of the same family (PEA) but which is in the rubber state at room temperature. Swelling studies showed that the specific equilibrium water content of PHEA falls from 1.6 for pure (unconfined) PHEA to values that range from 0.4 to 1, for the (net-PMMA)-ipn-(net-PHEA), whereas in the second IPNs family, the equilibrium water uptake of PHEA phase is, at least, the same as that of the pure PHEA (in some cases it is greater). This means that the expansion of the PHEA phase is not restricted by the confining hydrophobic component when this last is in the rubber state at room temperature. Whereas for the first IPNs the mechanical properties significantly increased (storage modulus at 37 °C from 0.25 to 2.5 GPa) compared with those of pure PHEA (25.12 MPa), little if any reinforcing effect was observed in the second type of IPNs. This is due to the fact that the glass transition of the PEA network takes place at a lower temperature than that of PHEA, so both components are in the rubbery state at room temperature. Both series behave differently also in dynamic water sorption experiments: the rigid PMMA network hinders the diffusion of water, yielding lower values of the apparent diffusion coefficients. By contrast, with the PEA polymer as network I this diffusion is similar to that of the pure PHEA homonetwork.     

水凝胶中NaOH的二维扩散性质研究

从实验与理论两方面研究NaOH在水凝胶体模中的二维扩散特性.引入化学反应项,建立了刻画NaOH在蛋白质中渗透的反应扩散方程,继而对OH-在凝胶中的时空分布及不同注射浓度、不同反应速率常数下OH-的浓度分布进行了定量研究.实验利用加入酚酞指示剂的水凝胶对NaOH的扩散范围进行了刻画,与计算结果较为一致.该方法为预测NaO...     

Synthesis of thermosensitive guar‐based hydrogels with tunable physico‐chemical properties by click chemistry

Thermosensitive guar‐based hydrogels are obtained in water solutions by copper‐catalyzed 1,3‐dipolar cycloaddition between alkyne‐functionalized guars and α,ω‐diazido‐poly[(ethylene glycol)‐co‐(propylene glycol)]. Characterization by TGA, HR‐MAS ¹H NMR, and rheology have shown that hydrogels with tunable physico‐chemical properties, such as crosslinking density, viscoelasticity, swelling ratio, and so forth, could be obtained by varying the guar molar mass, the degree of alkyne functionality, the guar/crosslinker weight ratio, and the reaction temperature. Based on swelling measurements, it has been shown that the thermal sensitiveness of guar‐based hydrogels is fast, reversible, and intimately related to the weight fraction of the thermosensitive crosslinker in the network. Finally, the monitoring of doxorubicin hydrochloride release has demonstrated the potential of these hydrogels as temperature‐dependent drug release devices. The robust, efficient, and orthogonal approach described herein represents a general approach towards the development of well‐controlled guar‐based hydrogels using α,ω‐diazido crosslinkers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2733–2742, 2010     

水溶性导电高分子聚噻吩及其水凝胶的掺杂行为研究

用碘和高氯酸作掺杂剂对水溶性导电高分子聚（3-羧甲基噻吩）及其水凝胶的掺杂行为进行了系统研究。结果发现水溶胀聚（3-羧甲基噻吩）凝胶及其高分子很容易被高氯酸或碘的水溶液进行掺杂，且其掺杂能力强烈依赖于掺杂剂溶液浓度。对碘掺杂的高分子溶液，其掺杂过程不很稳定同时伴随着脱掺杂过程的发生，而对于聚噻吩凝胶，高氯酸极易使其掺杂，而且一旦掺杂则在掺杂状态下具有相对的稳定性。     

温敏性纤维素/聚Ν-异丙基丙烯酰胺复合水凝胶的固体核磁共振表征及动力学研究

利用半互穿网络方法将具有温度响应的高分子聚N-异丙基丙烯酰胺( PNIPAM)与天然纤维素复合得到温敏性水凝胶。通过固体核磁共振的1 H,13 C CP/MAS(交叉极化/魔角旋转)和QCP(定量交叉极化)等实验手段对复合凝胶的结构进行了定性及定量研究,并利用固体静态变温核磁共振实验和偶极滤波-自旋扩散实验研究了复合凝胶中PNIPAM分子链段的动力学行为。