含铅聚合物微凝胶与硫化氢反应前后在良溶剂中的分子扩散行为

用溶液聚合法制备出轻度交联的含铅微凝胶,用光子相关光谱技术测定其在良溶剂中与H₂S反应前、后的扩散行为,由外推法得到在浓度无限稀时的分子扩散系数,给出微凝胶的流体力学半径。结果表明:相同量的含铅微凝胶在不同的初始浓度下与H₂S反应,生成含PbS纳米微粒的凝胶;但其体积增大不同,这说明H₂S与含铅微凝胶的反应既可以在分子内也可以在分子间进行,分子间的反应使含硫化铅微凝胶扩散系数随浓度的变化曲线的线性范围变小。     

反应型凝胶剂2,4-二烷脲基甲苯衍生物及有机溶剂的室温凝胶化研究

通常制备有机分子凝胶是在高温下溶解凝胶剂,凝胶剂分子在冷却过程中进行自组装并使有机溶剂凝胶化.该方法限制了某些低沸点溶剂的凝胶化.利用甲苯二异氰酸酯与烷基胺的高反应活性,制备了3种反应型凝胶剂.这种反应型凝胶剂能以较低的浓度在室温下使某些芳香族和卤代烃溶剂形成热可逆的有机分子凝胶.场发射扫描电镜表明这种反应型凝胶剂在有机溶剂中自组装形成纤维状三维网络结构.随着烷基胺中的烷基链长度不同,形成的纤维状聚集体的形态也不同.FT-IR和1H NMR研究表明分子间氢键作用是反应型凝胶剂自组装的驱动力.通过XRD和分子模拟推测了其聚集体的结构形态.     

反应型二烷基脲凝胶剂及有机溶剂的室温凝胶化研究

通常制备有机分子凝胶是在高温下溶解凝胶剂,凝胶剂分子在冷却过程中进行自组装并使有机溶剂凝胶化。该方法限制了某些低沸点溶剂的凝胶化。利用甲苯二异氰酸酯与烷基胺的高反应活性,制备了三种不同烷基链长的反应型凝胶剂甲苯–2, 4–二（N, N’ –烷基）脲。这种反应型凝胶剂能以较低的浓度在室温下使某些芳香族和卤代烃溶剂中形成热可逆的有机分子凝胶。不同烷基链长的亲溶剂作用以及溶剂性质对有机分子凝胶的形成有较大影响。场发射扫描电镜表明这种反应型凝胶剂在有机溶剂中自组装形成纤维状三维网络结构。烷基链长度不同,形成的纤维状聚集体的形态也不同。红外光谱（FT-IR）和核磁共振波谱（1H-NMR）研究表明分子间氢键作用是这种凝胶剂自组装的驱动力。通过X射线衍射（XRD）和分子模拟推测了其聚集体的结构形态。     

反应型二烷基脲凝胶剂及有机溶剂的室温凝胶化研究

通常制备有机分子凝胶是在高温下溶解凝胶剂,凝胶剂分子在冷却过程中进行自组装并使有机溶剂凝胶化。该方法限制了某些低沸点溶剂的凝胶化。利用甲苯二异氰酸酯与烷基胺的高反应活性,制备了三种不同烷基链长的反应型凝胶剂甲苯–2, 4–二（N, N’ –烷基）脲。这种反应型凝胶剂能以较低的浓度在室温下使某些芳香族和卤代烃溶剂中形成热可逆的有机分子凝胶。不同烷基链长的亲溶剂作用以及溶剂性质对有机分子凝胶的形成有较大影响。场发射扫描电镜表明这种反应型凝胶剂在有机溶剂中自组装形成纤维状三维网络结构。烷基链长度不同,形成的纤维状聚集体的形态也不同。红外光谱（FT-IR）和核磁共振波谱（1H-NMR）研究表明分子间氢键作用是这种凝胶剂自组装的驱动力。通过X射线衍射（XRD）和分子模拟推测了其聚集体的结构形态。     

纳米结构型PMAA/CdS复合微球的微凝胶模板法制备研究

以微凝胶为模板,利用微凝胶三维网络结构对无机沉积反应的限域和导向作用,制备了具有核-壳结构的聚甲基丙烯酸/硫化镉(PMAA/CdS)有机/无机复合微球材料.复合微球的制备包含两个基本步骤首先,以反相乳液聚合法得到包含Cd(Ac)2的聚甲基丙烯酸微凝胶;然后,在搅拌过程中向反应体系中缓慢通人H2S气体,使镉离子沉积为CdS,经洗涤处理后得到PMAA/CdS复合微球.SEM观察表明,复合微球表面呈现均一的微纳米结构,这种结构可因微球制备条件的不同而不同.而且,超声处理可使微球表面趋于光滑.X射线衍射分析表明复合微球中CdS处于晶态,具有立方结构.此外,复合微球因CdS的存在而具有光致发光特性.     

苯硼酸类糖敏感微凝胶制备及其糖敏感性研究

制备了以葡聚糖作为交联剂的氨基苯硼酸类糖敏感微凝胶,用1H-NMR和FT-IR表征了其结构。利用微凝胶的不同条件下的粒径变化,深入研究了该类凝胶对糖浓度的刺激响应行为。结果表明,葡聚糖的引入使微凝胶在生理条件下具有更加优秀的依糖刺激响应行为。     

循环伏安法研究超分子有机凝胶中二茂铁的扩散

4,4′-二(硬脂酰胺基)-二苯甲烷(BSAPM)在LiClO4/碳酸丙烯酯(PC)中能形成超分子有机凝胶。用循环伏安法研究了包埋在凝胶中的二茂铁的氧化还原行为。结果表明,有机凝胶内的二茂铁仍具有氧化还原活性,其氧化还原行为是受扩散控制的单电子可逆转移过程。与溶液相比,最低化凝胶浓度下凝胶中二茂铁和二茂铁离子的扩散系数分别从5.62×10-6cm2/s和6.47×10-6cm2/s下降为3.32×10-6cm2/s和4.41×10-6cm2/s,且随凝胶因子浓度的增加,凝胶中二茂铁和二茂铁离子的扩散系数降低。     

温敏聚合物/纳米CuS复合微球在肿瘤光热化学联合治疗中的应用

利用湿化学法合成了具有光热效应的纳米硫化铜(Cu S)颗粒,采用沉淀聚合法,以N-异丙基丙烯酰胺(NIPAAm)和N-乙烯基吡咯烷酮(NVP)为共聚单体,锂藻土(laponite)作为交联剂,吸附纳米硫化铜,制备出兼具光热效应和温敏响应性的复合微凝胶[P(NIPAAm-co-NVP)/Cu S](NNC/Cu S),并测试其载药和药物缓释性能.实验结果表明,制备的纳米Cu S和NNC/Cu S复合微凝胶均在近红外区有很宽的光谱吸收带,在980 nm(0.51 W/cm2)激光的辐照条件下,NNC/Cu S复合微凝胶具有良好的光热效应,温度在8 min内可以升至51.9℃,对于Hela细胞杀伤效果明显,并随着激光照射时间的延长效果越好.复合微凝胶的载药量为0.15mg/mg,在p H=5.5的PBS缓冲液中累积药物释放为75%,高于p H=7.4的63%.同时光热效应对于温敏性载药微球的药物释放具有有效地调控作用,在药物释放阶段,激光照射段药物释放率明显高于未加激光照射段.另外聚合物与纳米Cu S的复合改善了纳米Cu S对于细胞的毒性,NNC/Cu S复合微凝胶细胞存活率为90.9%高于纳米Cu S的63%.     

pH响应型P(HEMA/MAA)纳米微凝胶分散液的凝胶化行为和流变性能

制备了在修复受损组织方面有应用潜能的纳米级聚(甲基丙烯酸羟乙酯/甲基丙烯酸) (P(HEMA/MAA))微凝胶; 采用试管倒转法对不同pH值和浓度的P(HEMA/MAA)微凝胶分散液的凝胶化相转变行为进行了研究; 借助椎板流变仪考察了低浓度和高浓度微凝胶分散液的流变性能, 并对pH触发物理凝胶化相转变机理进行了推测. 结果表明: 在生理pH值环境下, 一定浓度的P(HEMA/MAA)微凝胶分散液可以发生凝胶化相转变形成凝胶态, pH=7时, HEMA/MAA进料摩尔比为8/2的微凝胶分散液凝胶化后得到的凝胶力学性能最佳, 最大弹性模量(G')可达7.58×10³ Pa; P(HEMA/MAA)微凝胶颗粒在不同条件下具有不同的溶胀效果, 导致低浓度分散液的表观粘度发生相应的变化, 并由此推测出微凝胶颗粒的溶胀过程由外及内, 分为三个阶段; 高浓度微凝胶分散液发生凝胶化相转变主要是由颗粒间或颗粒与分散介质间形成的空间静电稳定作用和氢键共同作用引起的.     

以Schiff base为配体的Cu(Ⅱ)-金属凝胶的制备和表征

以间苯二甲醛分别与异烟肼、烟酸酰肼和2-吡啶甲酰肼反应,合成了3种含吡啶环的Schiff base配体间苯二甲醛双缩4-吡啶甲酰腙(S1)、间苯二甲醛双缩3-吡啶甲酰腙(S2)和间苯二甲醛双缩2-吡啶甲酰腙(S3);测试了这3个化合物与醋酸铜通过配位作用在不同溶剂中形成金属凝胶的能力,结果发现,配体S1与醋酸铜在DMF/H_2O和DMSO/H_2O的混合溶剂中、配体S3与醋酸铜在DMF/H_2O的混合溶剂中均可以形成金属凝胶。胶凝测试结果表明,吡啶环上N原子位置的不同,对化合物形成金属凝胶的能力有极大影响。利用扫描电子显微镜(SEM)观察了金属凝胶的微观形貌,结果表明,配体分子的结构对金属凝胶的微观形貌也有较大影响;红外光谱和紫外可见光谱的研究证明了配位作用在金属凝胶形成过程中的推动作用;X射线衍射分析(XRD)研究表明,配体S1与醋酸铜在两种混合溶剂中形成的金属凝胶均表现出了四方堆积结构。     

铅离子敏感N-异丙基丙烯酰胺共聚物微凝胶的制备

采用对N-异丙基丙烯酰胺-丙烯酸共聚微凝胶进行改性的方法合成了含苯并18-冠-6功能基团的PNIPAM微凝胶.红外和核磁光谱等手段证明苯并18-冠-6基团被引入到微凝胶中.改性后的微凝胶仍具有很好的温敏性,但是相转变温度由改性前的30℃提高到42℃,并且溶胀度也大大增加.在不控制离子强度的条件下微凝胶的粒径随Na+浓度增加而减小,但是随Pb2+浓度增加微凝胶粒径先减后增.在控制离子强度不变的条件下Na+浓度对微凝胶的粒径影响很小,但是随Pb2+浓度增加微凝胶粒径明显增大,显示较强的铅离子敏感性。     

Polypyrrole/poly(N‐isopropylacrylamide‐co‐acrylic acid) thermosensitive and electrically conductive composite microgels

The electrically conductive polypyrrole/dodecylbenzene sulfonic acid/poly(N‐isopropylacrylamide‐co‐acrylic acid) (PPy/DBSA/poly(NIPAAm‐co‐AA)) composite microgels were synthesized by a chemical oxidation of pyrrole in the presence of DBSA as the primary dopant, and poly(NIPAAm‐co‐AA) microgels as the polymeric codopant and template, in which APS was used as the oxidant. It was proposed to prepare “intelligent” polymer microgel particles containing both thermosensitive and electrically conducting properties. The polymerization of pyrrole took place directly inside the microgel networks, leading to formation of composite microgels and the morphology was observed by transmission electron microscope. PPy particles interacted strongly with microgels, as the acid groups of microgels acted as the polymeric codopant. The composite microgels thus formed showed electrically conducting behavior dependent on humidity and temperature. At temperatures lower than lower critical solution temperature, the conductivity decreased with increasing the humidity and a small hysteresis phenomenon was observed. The hysteresis became indistinct when temperature was near volume phase transition temperature. However, after the treatment of high temperature and high humidity, the conductivity increased surprisingly due to the structure reorganization inside the composite microgels. The distinctive functionality of the PPy composite microgels was expected to be utilized in many attractive applications. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1648–1659, 2006     

Phototactic Poly(N-isopropyl acrylamide) Microgels with Photoresponsive Property

Smart functional microgels hold great potential in a variety of applications, especially in drug transportation. However, current drug carriers based on physiological internal stimuli cannot efficiently orientate to designated locations. Therefore, it is necessary to introduce the self-propelled particles to the drug release of the microgels. In order to study self-propulsion of microgels induced by light, it is also a challenge to prepare micron-sized microgels so that they can be observed directly under optical microscopes. In this work, phototactic microgels with photoresponsive properties are prepared. The microgel particles can be observed by confocal laser scanning microscopy. The photoresponsive properties of microgels are fully investigated by various instruments. Light can also regulate the state of the microgel solution, making it switch between turbidity and clarity. The phototaxis of particles irradiated by UV light was studied, which may be used for microgels enrichment and drug transportation and release.     

Equilibrium and kinetic aspects of the uptake of poly(ethylene oxide) by copolymer microgel particles of N-isopropylacrylamide and acrylic acid

The use of microgels for controlled uptake and release has been an area of active research for many years. In this work copolymer microgels of N-isopropylacrylamide (NIPAM) and acrylic acid (AAc), containing different concentrations of AAc and also cross-linking monomer, have been prepared and characterized. These microgels are responsive to pH and temperature. As well as monitoring the equilibrium response to changes in these variables, the rates of swelling/de-swelling of the microgel particles, on changing either the pH or the temperature, have also been investigated. It is shown that the rate of de-swelling of the microgel particles containing AAc is much faster than the rate of swelling, on changing the pH appropriately. This is explained in terms of the relative mobilities of the H(+) and Na(+) ions, in and out of the particles. It was observed that the microgels containing AAc, at pH 8, de-swelled relatively slowly on heating to 50 degrees C from 20 degrees C. This is attributed to the resistance to collapse associated with the large increase in counterion concentration inside the microgel particles. The swelling and de-swelling properties of these copolymer microgels have also been investigated in aqueous poly(ethylene oxide) (PEO) solutions, of different MW (2000-300 000). The corresponding absorbed amounts of PEO from solution onto the microgels have also been determined using a depletion method. The results, as a function of AAc content, cross-linker concentration, PEO MW, pH, and temperature, have been rationalized in terms of the ease and depth of penetration of the PEO chains into the various microgel particles and also the H-bonding associations between PEO and either the -COOH of the AAc moeities and/or the H of the amide groups (much weaker). Finally, the adsorption and desorption of the PEO molecules in to and out of the microgel particles have been shown to be extremely slow compared to normal diffusion time scales for polymer adsorption onto rigid surfaces.     

Swelling Kinetics of Microgels Embedded in a Polyacrylamide Hydrogel Matrix

Composite hydrogels—macroscopic hydrogels with embedded microgel particles—are expected to respond to external stimuli quickly because microgels swell much faster than bulky gels. In this work, the kinetics of the pH‐induced swelling of a composite hydrogel are studied using turbidity measurements. The embedded microgel is a pH‐ and thermosensitive poly(N‐isopropylacrylamide‐co‐acrylic acid) microgel and the hydrogel matrix is polyacrylamide. A rapid pH‐induced swelling of the embedded microgel particles is observed, confirming that composite hydrogels respond faster than ordinary hydrogels. However, compared with the free microgels, the swelling of the embedded microgel is much slower. Diffusion of OH^? into the composite hydrogel film is identified as the main reason for the slow swelling of the embedded microgel particles, as the time of the pH‐induced swelling of this film is comparable to that of OH^? diffusion into the film. The composition of the hydrogel matrix does not significantly change the characteristic swelling time of the composite hydrogel film. However, the swelling pattern of the film changes with composition of the hydrogel matrix.     

Polyurethane acrylate microgel synthesized by emulsion polymerization using unsaturated self-emulsified polymer

Polyurethane (PU) acrylate microgels were obtained by emulsion polymerization of self-emulsified PU acrylate terminated by 2-hydroxyethyl methacrylate without any extra emulsifier and crosslinker. Moreover, the PU acrylate was also used as stabilizer and crosslinker to synthesize poly(methyl methacrylate) (PMMA)–PU composite microgels via emulsion polymerization, which provided a new method to synthesize PU microgels and their composite microgels. The kinetics of microgel synthesis was studied by gel permeation chromatography. The dynamic rheological behaviors indicated that a crosslinked structure was formed. The frequency dependency of the loss tangent and complex viscosities showed strong relationships with the microgel structure. Those microgels with rigid PMMA core showed higher ability to slide than the soft PU acrylate microgel, which had influence on the changing of loss tangent with frequency. All the microgels swollen in tetrahydrofuran exhibited high viscosities and strong shear-thinning behaviors. As a sort of flexible microgel, the PU microgel was able to form a coherent film at room temperature, which was distinct from hard microgels.     

Highly regenerable ionic liquid microgels as inherently metal‐free green catalyst for H2 generation

Polymeric ionic liquid (PIL) microgel of poly([2‐(methacryloyloxy)ethyl]trimethylammonium chloride) (p(MTMA)) was synthesized by using an inverse suspension polymerization technique. The anion‐exchanged PIL microgels via chloride replacement from p(MTMA) were prepared as p(MTMA)‐potassium thiocyanate (p(MTMA)‐KSCN), p(MTMA)‐sodium tetrafluoroborate (p(MTMA)‐NaBF₄), and p(MTMA)‐sodium dicyanamide (p(MTMA)‐NaN(CN)₂) microgels by treatment with corresponding salts of potassium thiocyanate (KSCN), sodium tetrafluoroborate NaBF₄, and sodium dicyanamide NaN(CN)₂ in aqueous media. The prepared microgels were found to be efficient metal‐free catalysts, and their catalytic activity in H₂ production from the methanolysis of NaBH₄ was investigated. Moreover, various parameters affecting H₂ production such as the effect of microgel size, the concentration of NaBH₄, the effect of the anion in the microgel, the reusability of the microgel, and temperature were investigated. The Ea value calculated for the methanolysis reaction of NaBH₄ catalyzed by p(MTMA) microgels was found as 24.1 ± 0.7 kJ mol⁻¹ ranging from −15 to 45°C, and this Ea value is lower than some Ea values for the same reaction. Interestingly, 10‐time successive use of p(MTMA) microgel as catalyst in NaBH4 methanolysis reduced its catalytic activity to 49%, whereas the anion‐exchanged forms of p(MTMA) microgel, p(MTMA)‐KSCN, p(MTMA)‐NaBF₄, and p(MTMA)‐NaN(CN)₂ only reduced their catalytic activity to 89, 86, and 79%, respectively, after 10 consecutive uses. Therefore, these anion‐exchanged microgel catalysts are highly efficient in comparison with virgin p(MTMA) microgels for regenerable H₂ generation from the methanolysis of NaBH₄.     

Influence of charge density on the swelling of colloidal poly(N-isopropylacrylamide-co-acrylic acid) microgels

The volume phase transition of colloidal poly(N-isopropylacrylamide-co-acrylic acid) microgels depends in a complex way on the effective charge density within the polymer network. A series of monodisperse PNIPAM/AAc microgels with different content of acrylic acid were synthesized by surfactant-free emulsion polymerization employing sonication instead of a conventional stirring technique. Subsequently, the colloids were characterized by dynamic light scattering and electron microscopy. Potentiometric titrations provided the amount of carboxyl groups incorporated into the copolymer. The effective charge density was systematically controlled by the content of acrylic acid monomers, the pH value of the suspension, and the salt concentration. The hydrodynamic dimensions of the microgels have been measured by dynamic light scattering. The swelling/deswelling behavior is determined by the delicate balance between hydrophobic attraction of NIPAM and the repulsive electrostatic interactions of the carboxylate group of the acrylic acid moieties. Compared to their macroscopic counterparts the charged microgel particles show a significantly different swelling/deswelling behavior. This manifests in the occurrence of a two-step volume phase-transition process with increasing acrylic acid content. Hydrogen bonding has to be considered to understand this two step volume phase transition uniquely observed for colloidal microgels. Another interesting phenomenon presented here is the reversible formation of well-defined aggregates at low pH and under high salt conditions.     

UV cured transparent films including non‐aqueous conductive microgels

UV cured transparent films containing non‐aqueous conductive microgels coated with poly(aniline)/dodecyl benzenesulfonic acid(DBSA) were obtained. The conductive microgels were prepared by interface polymerization of aniline/DBSA in the presence of non‐aqueous polymeric microgels. The electrical conductivity and the particle size of the prepared conductive microgel were 0.5 S/cm and 58 nm, respectively. The prepared conductive microgels were easily blended with a UV curable coating formulation, and then were cured to make highly optically transparent films. For the UV cured film containing about 35 wt% of the conductive microgels, a surface resistance in the range of 10⁷ to 10⁸ Ω/square was obtained. In a polar cosolvent, such as NMP and m‐cresol, the critical volume was shifted to the lower range, with a value of 10 wt%. The UV cured films containing the conductive microgels exhibited good electrical stability against the thermal aging and humidity. Copyright © 2002 John Wiley & Sons, Ltd.