聚N－烷基丙烯酰胺类凝胶及其温敏特性

研制成功５种聚Ｎ－烷基丙烯酰胺类温敏凝胶：聚Ｎ－异丙基丙烯酰胺（ＰＮＩＰＡ），聚Ｎ－异丙基丙烯酰胺＋甲基丙烯酰胺（ＰＮＩＰＡ／ＭＡＡ），聚Ｎ，Ｎ－二乙基丙烯酰胺（ＰＮＤＥＡ），聚Ｎ－正丙基丙烯酰胺（ＰＮＮＰＡ），聚Ｎ，Ｎ－二乙基丙烯酰胺＋Ｎ－叔丁基丙烯酰胺（ＰＮＤＥＡ／ＮＴＢＡ），并系统研究了这些凝胶的温敏相交特性．以聚Ｎ－异丙基丙烯酰胺（ＰＮＩＰＡ）凝胶相交特性为基础的凝胶萃取过程对牛血清白蛋白和兰葡聚糖溶液的浓缩实验表明，凝胶萃取对于浓缩和制备贵重生化制品是很有效的．     

温度及pH敏感聚（丙烯酸）／聚（N—异丙基丙烯酰胺）互穿聚合物网络水凝胶的...

合成聚（丙烯酸）／聚（Ｎ－异丙基丙烯酰胺）互穿聚合物网络（ＰＡＡｃ／ＰＮＩＰＡ ＩＰＮ）水凝胶，具有温度及ｐＨ双重敏感特性。这种水凝胶在弱碱性条件下的溶胀率远大于酸性条件下的溶胀率。在酸性条件下，随着温度上升，凝胶的溶胀率也随之逐渐上升；而在弱碱性条件下，温度低于聚（Ｎ－异丙基丙烯酰胺）（ＰＮＩＰＡ）的较低临界溶解温度（ＬＣＳＴ）时，溶胀率也随着温度的上升而上升，而温度达到ＬＣＳＴ时，凝胶的溶胀率     

温度及pH敏感聚(丙烯酸)/聚(N-异丙基丙烯酰胺)互穿聚合物网络水凝胶的合成及性能研究

合成聚（丙烯酸）／聚（Ｎ 异丙基丙烯酰胺）互穿聚合物网络（ＰＡＡｃ／ＰＮＩＰＡＩＰＮ）水凝胶，具有温度及ｐＨ双重敏感特性．这种水凝胶在弱碱性条件下的溶胀率远大于酸性条件下的溶胀率．在酸性条件下，随着温度上升，凝胶的溶胀率也随之逐渐上升；而在弱碱性条件下，温度低于聚（Ｎ 异丙基丙烯酰胺）（ＰＮＩＰＡ）的较低临界溶解温度（ＬＣＳＴ）时，溶胀率也随着温度的上升而上升，当温度达到ＬＣＳＴ时，凝胶的溶胀率突然急剧下降，并随着温度的逐渐上升而下降．     

新型阴离子型温敏水凝胶

新型阴离子型温敏水凝胶王昌华，曹维孝（北京大学化学与分子工程学院，北京，１００８７１）关键词温敏水凝胶，溶胀比，Ｎ－异丙基丙烯酰胺１９８４年Ｔａｎａｋａ等人［１］发现Ｎ－异丙基丙烯酰胺（ＮＩＰＡ）与Ｎ，Ｎ－亚甲基双丙烯酰胺（ＭＢＡ）的微交联共聚体，在...     

聚N—异丙基丙烯酰胺溶液的温度依赖关系

用自由基聚合法合成了聚Ｎ－异丙基丙烯酰胺（ＰＮＩＰＡＡＭ）样品，用乌氏粘度计考查了该聚合物的四氢呋喃（ＴＨＦ）溶液和水溶液的粘度与温度的依赖关系。发现ＰＮＩＰＡＡＭ－ＴＨＦ体系的特性粘数随温度升高而增大，ＰＮＩＰＡＡＭ－Ｈ２Ｏ体系的特性粘数－温度曲线表现出较为复杂的变化规律。并用实验确定的特性粘数对合成样品的分子量进行了表征Ｍｎ＝８．４４×１０＾５ｇ·ｍｏｌ＾－１。     

聚N-异丙基丙烯酰胺溶液的粘度的温度依赖关系

用自由基聚合法合成了聚Ｎ 异丙基丙烯酰胺（ＰＮＩＰＡＡＭ）样品，用乌氏粘度计考查了该聚合物的四氢呋喃（ＴＨＦ）溶液和水溶液的粘度与温度的依赖关系．发现ＰＮＩＰＡＡＭ ＴＨＦ体系的特性粘数随温度升高而增大，ＰＮＩＰＡＡＭ Ｈ２Ｏ体系的特性粘数 温度曲线表现出较为复杂的变化规律．并用实验确定的特性粘数对合成样品的分子量进行了表征Ｍｎ＝８４４×１０５ｇ·ｍｏｌ－１．     

激光光散射表征聚N－异丙基丙烯酰胺的分子量分布

采用自由基聚合法合成了聚Ｎ－异丙基丙烯酰胺（ＰＮＩＰＡＡＭ）样品，由激光光散射法（ＬＬＳ），包括绝对累积散射光强的角度依赖性（静态ＬＬＳ）和线宽分布的角度依赖性（动态ＬＬＳ）表征了合成的ＰＮＩＰＡＡＭ样品的分子量分布。通过对动态光散射测得的电场－电场时间相关函数的拉普拉斯变换，求得平动扩散系数分布Ｇ（Ｄ）；结合静态和动态光散射测量的结果，即Ｍ_ｗ和Ｇ（Ｄ），确定了ＰＮＩＰＡＡＭ样品的平动扩散系数Ｄ对分子量Ｍ的标定关系式Ｄ＝２．８４×１０~（－４）Ｍ~（－０．５５），并将Ｇ（Ｄ）转换成分子量分布Ｆ_ｗ（Ｍ）．     

N-异丙基丙烯酰胺/N-乙烯基吡咯烷酮水凝胶的研究

研究了用Ｎ,Ｎ－亚甲基双丙烯酰胺作交联剂,Ｎ－异丙基丙烯酰胺／Ｎ－乙烯基吡咯烷酮共聚物水凝胶的合成与性能。结果表明,ＮＶＰ能显著延长共聚体系的凝胶化时间,但对共聚物的体积相变温度影响并不十分显著。当Ｎ－乙烯基吡咯烷酮的配料摩尔比（Ｎ－乙烯基吡咯烷酮／Ｎ－异丙基丙烯酰胺＋Ｎ－乙烯基吡咯烷酮）＝０．０１时,水凝胶呈现最大Ｔｃ和平衡溶胀胀比。当温度低于Ｔｃ时共的在水中的平衡溶胀比与Ｎ－异丙基丙烯酰胺和Ｎ－乙烯基吡咯烷酮的配料比有关;Ｎ－乙烯基吡咯烷酮配料摩匀比〈０．０１,平衡溶胀比随Ｎ－乙烯基吡咯烷酮配料摩尔比的增加而增加;Ｎ－乙烯基吡咯烷桐配料摩尔比〉０．０１,平衡溶胀比随Ｎ－乙烯基吡咯烷酮配料摩尔浓度的增加而降低。同Ｎ－并异丙烯酰胺均聚物水凝胶相比,共聚物水凝胶具有较好的温敏响应性。ＤＳＣ和ＴＧＡ研究表明,Ｎ－乙     

(7-N,N-二甲氨基)香豆素基-3-甲酸乙酯/二芳基碘鎓盐光敏引发聚合反应体系

本工作合成了（７－Ｎ,Ｎ－二甲氨基）香豆素基－３－甲酸乙酯（ＥＤＡＣＦ）光敏剂．在光作用下,激发态的ＥＤＡＣＦ分子与二芳基碘盐ＯＰＰＩＰ分子之间发生电子转移反应,伴随发生ＥＤＡＣＦ的褪色反应和ＯＰＰＩＰ的光解反应,后者生成具有引发活性的芳基自由基．由于ＥＤＡＣＦ具有ＣＴ态特性,使得它与ＯＰＰＩＰ之间的光电子转移反应速度随着溶剂极性增加明显减慢．ＥＤＡＣＦ／ＯＰＰＩＰ体系可有效地引发ＭＭＡ聚合反应,聚合反应动力学方程为Ｒｐ＝Ｋ［ＯＰＰＩＰ］０．４７［ＥＤＡＣＦ］０．４２［ＭＭＡ］０．９８．     

疏水化修饰的聚N-异丙基丙烯酰胺高分子的水溶液性质研究

为了研究不同疏水化修饰的聚Ｎ 异丙基丙烯酰胺（ＰＮＩＰＡＭ）高分子的水溶液性质,合成了一系列Ｎ 异丙基丙烯酰胺（ＮＩＰＡＭ）和长链丙烯酸酯及丙烯酸胆固醇酯的共聚物．利用表面张力法证实了该类共聚物在室温下都具有良好的表面活性,在水溶液中能够形成胶束．利用荧光探针法,研究了共聚物的低温临界溶液温度（ＬｏｗｅｒＣｒｉｔｉｃａｌＳｏｌｕｔｉｏｎＴｅｍｐｅｒａｔｕｒｅ,ＬＣＳＴ）,发现,随着丙烯酸酯碳链及其配比（摩尔投料比）的变化,共聚物的ＬＣＳＴ变化不明显,但它们都比均聚的ＰＮＩＰＡＭ要低;利用荧光偏振法研究了共聚物在水溶液中的微粘度,发现其微粘度不随共聚物中丙烯酸酯链长和配比的变化而变化,说明了该类共聚物在室温下能够形成相类同的胶束内核．     

ESR study of thermal destruction of polypyromellitimides

A mechanism for thermal degradation of poly-N, N′-[p, p′-diphenyl] -pyromellitimide(resin I), poly-N, N′-[(m, m′-dimethyl)-p,p′-diphenyl] pyromellitimide-(resin II), and poly-N, N′-[(m, m′-dimethoxy)-p, p′-diphenyl] pyromellitimide (resin III) has been studied by means of ESR spectroscopy and pyrolysis gas chromatography. The concentration of paramagnetic centres formed as a result of free-radical scission of C-C and C-N bonds and the parameters of the ESR signal (ΔH_max and g-value) are strictly dependent on temperature of resin decomposition. The results suggest quite different mechanisms for thermal destruction of resin III and that for the other two, namely formation of the benzoxazole ring as an intermediate stage in decomposition.     

Multifunctionalised cationic fullerene adducts for gene transfer: design, synthesis and DNA complexation

Cationic poly-N,N-dimethylfulleropyrrolidinium derivatives have been designed and synthesised to complex plasmid DNA for gene delivery.     

Thermal degradation of lyocell/poly-N-isopropylacrylamide graft copolymers gels

In the present work Lyocell fibers were subjected to graft copolymerization of poly-N-isopropylacrylamide (pNIPAAm) thermosensitive polymer. The thermal degradation and stability of lyocell/pNIPAAm copolymers gels were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). pNIPAAm/lyocell copolymers are thermally stable and more resistant to temperature than lyocell fibres. Thermal characterization was analyzed as a function of percentage by mass of the pNIPAAm grafted. It has been shown that for pNIPAAm/lyocell copolymers, degradation occurs at higher temperature when increasing the degree of grafting.     

Coagulation of Butadiene-Styrene Latex with Poly-N,N-dimethyl-2-hydroxypropylenammonium Chloride

The flocculating performance of a cationic polyelectrolyte, poly-N,N-dimethyl-2-hydroxypropylenammonium chloride, in recovery of butadiene-styrene rubber in the presence of sulfuric acid at various temperatures was studied. The kinetic curves of flocculation of SKS-30 ARK latex at various amounts of the flocculant added were obtained.     

Magnetic separation of polymer hybrid iron oxide nanoparticles triggered by temperature

The water dispersion of poly-N-isopropylacrylamide hybrid nanoparticles exhibited temperature-triggered magnetic separation behaviour: if the temperature switched between below and above 32 degrees C, the nanoparticles could be dispersed into water and reversibly separated by a magnetic field of 1.1 T.     

Amino-group-specific natural abundance nitrogen isotope ratio analysis in amino acids

Amino acid (AA) nitrogen (N) stable isotope ratio analysis has found a wide variety of important applications including indication of the trophic level of an organism, tracing N transfer within food webs, and monitoring of AA resynthesis during heterotrophic microbial reworking of organic matter. Despite its utility, the current methodology is difficult to employ consistently for natural abundance level precision. Here, we report a new and robust method for high-precision N-compound-specific isotope analysis (N-PCIA) for single-N-containing AAs and N-position-specific isotope analysis (N-PSIA) for poly-N AAs. First the amino-N in AAs was liberated and oxidized to NO2(-) by hypochlorite at high pH. The NO2(-) produced was then quantified colorimetrically with excess hypochlorite quenched using arsenite. Subsequently, buffered azide was used to reduce NO2(-) to N2O for isotope ratio analysis using a purge-and-trap isotope ratio mass spectrometer. In the case of glycine delta15N, the average precision was SD = 0.3 per thousand. Reaction yields and labeling experiments show that this oxidation reaction is highly specific, targeting the alpha-amino group (peptide-N) of most poly-N AAs. This permits specific determination of the delta15N of peptide-N in arginine, tryptophan, and histidine. In the case of lysine, however, the side-chain amino group was found to be partially labile to hypochlorite oxidation. Using isotope fractionation factors estimated from single-N analogues of lysine, the intramolecular delta15N of lysine was calculated by mass balance, and this generally agreed with results for the same sample material analyzed by a previously published enzymatic method. Our method has the advantages of being relatively rapid, robust, and applicable to all poly-N AAs. We have also found it to work well for determining total delta15N of amino-N in complex sample matrices that have not been susceptible to previous approaches.     

Direct immunoassay of estrone by capillary electrophoresis with laser-induced fluorescence detection

An immunoassay for estrone (E(1)) in women's serum, based on the competitive reaction between fluorescein-labeled complete antigen and E(1) with limited amount of anti-estrone monoclonal antibody is described. A thermally reversible hydrogel, poly-N-isopropylacrylamide (pNIPA), was added to the buffer to improve the reproducibility. With a laser-induced fluorescence (LIF) detector, the capillary electrophoretic immunoassay (CEIA) can be applied to determine E(1) at a concentration lower than 19.6 pg/mL. The E(1) levels in ten normal women's serum were measured at the range of 118.6-222.0 pg/mL.     

Effect of thermosensitive matrix-phase transition on urease-catalyzed urea hydrolysis

Temperature dependencies of kinetic and equilibrium parameters of urea hydrolysis catalyzed by native urease and the urease immobilized in a thermosensitive poly-N-isopropylacrylamide gel have been studied. The swelling ratio of the collapsed urease-containing gel is shown to increase in the presence of urea. Below a lower critical solution temperature (LCST) of the polymer, the immobilized u reaseactually has thesame catalytic properties as the native enzyme. At temperatures above LCST, the observed catalytic activity of the immobilized enzyme depends chiefly not only on the thermoreversible matrix state, but also on gel water content.     

Large-area organization of pNIPAM-coated nanostars as SERS platforms for polycyclic aromatic hydrocarbons sensing in gas phase

Here, a new surface enhanced Raman spectroscopy (SERS) platform suitable for gas phase sensing based on the extended organization of poly-N-isopropylacrylamide (pNIPAM)-coated nanostars over large areas is presented. This system yields high and homogeneous SERS intensities, and simultaneously traps organic chemical agents as pollutants from the gas phase. pNIPAM-coated gold nanostars were organized into parallel linear arrays. The optical properties of the fabricated substrates are investigated, and applicability for advanced sensing is demonstrated through the detection in the gas phase of pyrene traces, a well-known polyaromatic hydrocarbon.