接枝量对等离子体接枝聚异丙基丙烯酰胺开关的多孔膜的温度感应透过性的影响

The effect of graft yield on both the thermo-responsive hydraulic permeability and the thermo-respousive diffusional permeability through porous membranes with plasma-grafted poly(N-isopropylacrylamide) (PNIPAM)gates was investigated. Both thermo-respousive flat membranes and core-shell microcapsule membranes with a wide range of graft yield of PNIPAM were prepared using a plasma-graft pore-filling polymerization method. The grafted PNIPAM was formed homogeneously throughout the entire thickness of both the fiat polyethylene membranes andthe microcapsule polyamide membranes. Both the hydraulic permeability and the diffusional permeability were heavily dependent on the PNIPAM graft yield. With increasing the graft yield, the hydraulic permeability (water flux) decreases rapidly at 25℃ because of the decrease of the pore size; however, the water flux at 40℃ increases firstly to a peak because of the increase of hydrophobicity of the pore surface, and then decreases and finally tends to zero because of the pore size becoming smaller and smaller. For the diffusional permeability, the temperature shows different effects on the diffusional permeability coefficients of solutes across the membranes. When the graft yield was low, the diffusional coefficient of solute across the membrane was higher at temperature above the lower critical solution temperature (LCST) than that below the LCST; however, when the graft yield was high, the diffusional coefficient was lower at temperature above the LCST than that below the LCST. It is very important to choose or design a proper graft yield of PNIPAM for obtaining a desired thermo-respousive “on/off“ hydraulic or ditfusional permeability.     

聚(N-异丙基丙烯酰胺-co-丙烯酸)水凝胶对铜离子的体积响应动力学

采用微波辐射法制备了N-异丙基丙烯酰胺-co-丙烯酸共聚水凝胶,探讨了该水凝胶对Cu²⁺的响应动力学,并估算出此过程中水凝胶的体积收缩速率常数及其反应活化能,同时建立了Cu²⁺浓度对水凝胶体积收缩响应速率常数影响的数学关系模型。实验结果表明,水凝胶对Cu²⁺所产生的体积收缩响应符合拟一级动力学反应。在40～60℃水溶液中,水凝胶的收缩速率随溶液中Cu²⁺浓度的增高而加快,其反应活化能在36～42 kJ•mol^-1之间,且随着溶液中Cu²⁺浓度的增大而逐渐减小。重复性实验表明,该共聚水凝胶经过3次体积收缩(50.0℃溶液)/溶胀(6.0℃溶液)的循环实验,它在含Cu²⁺水溶液中对温度变化仍能保持高灵敏度的体积收缩/溶胀响应,而且其3次体积收缩/溶胀响应值几乎一样,有很好的重现性。     

多孔膜基材对等离子体接枝膜微观结构的影响

采用等离子体诱导接枝聚合法,在有机聚偏氟乙烯(PVDF)膜、尼龙(N6)膜和无机多孔阳极氧化铝(PAA)膜上接枝甲基丙烯酸(MAA),系统地研究了多孔膜基材及接枝工艺条件对接枝开关膜微观结构的影响。结果发现,对于PVDF基材膜,单体溶液脱气次数越多接枝率越大。对于不同类别的多孔膜基材,采用相同工艺条件接枝时,N6膜的接枝率高于PVDF膜,PAA膜接枝率最低。在接枝率相近的时候,接枝层在PVDF膜整个断面孔内和表面均存在,而N6膜则主要集中在表层。在PAA膜上接枝时发现,等离子体照射功率的强弱对基材膜的影响很大,当功率超过50W时,PAA膜表层就会被刻蚀而导致膜的质量减轻。     

N-异丙基丙烯酰胺功能性共聚物的结构及特性研究进展

N-异丙基丙烯酰胺共聚物是一种新型的智能材料,可用于制备药物控释材料、酶的固定材料、脱水剂等。概述了N-异丙基丙烯酰胺共聚物及其各类共聚单体的大分子结构、氢键效应及刺激响应性等特性。     

聚(N-异丙基丙烯酰胺)温敏微球的粒径及单分散性

Thermo-responsive poly (N-isopropylacrylamide-co-styrene ) [P(NIPAM-co-St)] hydrogel microspheres were prepared by surfactant-free emulsion polymerization. The effects of initiator dosage, stirring rate, phase ratio and polymerization time on particle size and monodispersity were investigated. The results showed that, with increasing initiator dosage, mean diameter increased slightly to a maximum, and then decreased drastically; meanwhile, the monodispersity of the particles became a little better at first, and then became worse significantly. With increasing stirring rate, particle diameter decreased while the monodispersity became worse. When the amount of phase rate increased, the mean diameter became larger simply, whereas the monodispersity became worse firstly and then became better again. As the polymerization proceeded, the mean diameter of the particles hardly changed, and the monodispersity became better gradually. The microspheres prepared under the optimum experimental conditions showed satisfactory particle size and monodispersity.     

pH敏感性和温敏性聚丙烯酸钠与聚N-异丙基丙烯酰胺互穿网络材料的合成及其溶胀行为的研究

制备了对湿度和pH值具有双重敏感性的PAANa/PNIPAM互穿网络（IPN）材料,测定了IPN的平衡溶胀度和在不同湿度和pH中的溶胀度变化的行为。结果显示,这种材料能分别在32℃和pH为5．5发生溶胀行为的突变,溶胀度突变范围明显高于以往文献所报道的类似材料的变化值。根据它在温度变化和pH值变化中的溶胀行为可以得知,在网络中这两种分链是独立作用的,但是相互之间又有影响。     

聚N-异丙基丙烯酰胺共聚物纳米膜的制备与表征

报道了一种制备性能良好的温敏性纳米膜的简易方法。首先采用自由基聚合法将N-异丙基丙烯酰胺、甲基丙烯酸羟丙酯和甲基丙烯酸(3-三甲氧基硅)丙酯等原料合成为新型的PNIPAAm共聚物。通过动态光散射、傅里叶变换红外光谱、核磁共振氢谱和凝胶渗透色谱等对终产物的温敏特性、化学结构和分子量进行研究。进而采用旋转涂膜法和加热退火法在硅片或玻璃片上制备PNIPAAm共聚物纳米膜,并采用接触角测量仪、原子力显微镜和椭圆偏振仪等技术手段检测了不同制膜溶液浓度和测试温度条件下共聚物膜的表面润湿性、表面结构和总体厚度。结果表明所制备的PNIPAAm共聚物及其纳米膜均具有温敏特性,且可用于干细胞的有效收获。     

侧链含芘基的聚N-异丙基丙烯酰胺的合成及性能

将N-异丙基丙烯酰胺（NIPAM）和甲基丙烯酸-β-(1-芘丁酰氧基)乙酯（PyBEMA）通过自由基溶液共聚合成了侧链含芘基的聚N-异丙基丙烯酰胺共聚物，并采用红外光谱、紫外光谱、核磁共振氢谱对共聚物进行了结构表征。研究了不同投料比对共聚物收率、组成和相对分子质量及其分布的影响。共聚物水溶液温敏性研究表明，共聚物是一类具有低临界溶解温度（LCST）温敏性聚合物，随着共聚物中的芘基含量的升高，其LCST下降；加入α-环糊精（α-CD）会引起共聚物LCST略微升高，而加入β-CD和γ-CD，会导致LCST降低，而且γ-CD引起LCST的降低更显著。共聚物水溶液荧光性能研究表明，共聚物在水中有轻微的疏水聚集，出现侧链芘基激基缔合物荧光。室温下，加入β-CD能够降低共聚物侧链芘基之间的疏水聚集。随着温度的升高，芘基的荧光强度（IM）先下降，后突然升高，然后达到稳定并略微下降；而芘激基缔合物的荧光强度（IE）先出现略微升高，然后基本保持不变，接着缓慢下降。I1/I3荧光强度比值随着温度的升高呈现下降趋势，在聚合物发生相转变时的温度区间内迅速降低。     

新型温敏性中空纤维膜的制备与表征

采用自由基聚合方法对中空纤维膜（hollow fiber membranes,HFMs）进行了N-异丙基丙烯酰胺（NIPAAm）的接枝聚合,制备了一系列PNIPAAm-g-HFMs,同时考察了成纤维细胞在PNIPAAm-g-HFMs表面的培养与降温脱附情况。傅里叶红外光谱和元素分析结果表明PNIPAAm成功地在中空纤维膜上接枝聚合。动态接触角分析结果显示,当温度降至LCST以下,PNIPAAm-g-HFMs表面接触角明显降低;蛋白黏附测定结果进一步证实了当温度发生改变时,PNIPAAm-g-HFMs表面呈现亲疏水性质变化,即具有温敏性。37℃时,成纤维细胞在HFMs-0.005,HFMs-0.01和HFMs-0.05表面均能正常黏附、铺展与增殖;而HFMs-0.2不适宜细胞的黏附与生长。降温孵育后,黏附于PNIPAAm-g-HFMs表面的细胞发生明显的形态变化并从其表面发生脱附,细胞脱附率高达90%以上。以上实验结果表明,PNIPAAm-g-HFMs具有良好的温敏性,可实现细胞的降温脱附,可与生物反应器相结合用于贴壁型细胞的大规模扩增与降温收获。     

快速响应聚(N-异丙基丙烯酰胺)水凝胶的制备及性能

以N-异丙基丙烯酰胺为单体、N,N′-亚甲基双丙烯酰胺为交联剂、过硫酸铵为引发剂、N,N,N,′N′-四甲基乙二胺为加速剂,在不同浓度的羧甲基纤维素的水溶液中,在低温下聚合/交联制备了一系列快速响应的温度敏感性聚(N-异丙基丙烯酰胺)水凝胶。用SEM观察了其表面形态,测定了不同温度下达到平衡时水凝胶的溶胀比,研究了水凝胶的去溶胀动力学。结果表明,与传统水凝胶相比,该水凝胶的溶胀性能有所提高,并且对温度的变化具有较快的响应速率。以质量分数为0.75%的羧甲基纤维素水溶液中制备的水凝胶为例,该水凝胶在20℃时的溶胀比为21.4,而传统水凝胶在相同温度时的溶胀比仅为12.9;该水凝胶在1 m in内失去60%的水,在4 m in内失去约80%的水,而传统水凝胶在15 m in内仅失去66%左右的水。     

分散聚合法合成聚(N-异丙基丙烯酰胺)温敏性微凝胶

以PVP为稳定剂,在水或醇/水介质中通过分散聚合法合成出聚（N-异丙基丙烯酰胺）（PNIPAM）温敏性微凝胶。研究结果表明,可通过改变稳定剂用量和分散介质极性来控制PNIPAM微凝胶的大小,这两种因素对PNIPAM微凝胶的溶胀比有明显的影响,而对其相转变行为影响不大;交联剂用量对PNIPAM微凝胶的粒径、溶胀比和相转变行为都有比较明显的影响。PNIPAM微凝胶可能主要通过接枝共聚物聚结机理成核,通过初级粒子之间的聚并完成粒子增长过程。     

Effect of Graft Yield on the Thermo-Responsive Permeability Through Porous Membranes with Plasma-Grafted Poly(N-isopropylacrylamide)Gates

The effect of graft yield on both the thermo-responsive hydraulic permeability and the thermo-responsive diffusional permeability through porous membranes with plasma-grafted poly(AT-isopropylacrylamide) (PNIPAM) gates was investigated. Both thermo-responsive flat membranes and core-shell microcapsule membranes with a wide range of graft yield of PNIPAM were prepared using a plasma-graft pore-filling polymerization method. The grafted PNIPAM was formed homogeneously throughout the entire thickness of both the flat polyethylene membranes and the microcapsule polyamide membranes. Both the hydraulic permeability and the diffusional permeability were heavily dependent on the PNIPAM graft yield. With increasing the graft yield, the hydraulic permeability (water flux) decreases rapidly at 25℃ because of the decrease of the pore size; however, the water flux at 40℃ increases firstly to a peak because of the increase of hydrophobicity of the pore surface, and then decreases and finally tends to zero because o     

Thermosensitive surface properties of polyethylene film with poly(N-isopropylacrylamide) chains prepared by corona discharge induced grafting

Polyethylene (PE) film was treated by corona discharge and then grafted with N-isopropylacrylamide (NIPAAm) for modification of the surface. The grafted amount was determined by gravimetry and the surface morphology was observed by using a scanning electron microscope. The surface analysis was carried out with a x-ray photoelectron spectroscopy and electron probe microanalysis. It was clarified that grafting was limited surface and there was no change of the surface morphology after grafting. The water absorption at various temperature under the absolute humidity (11.4 g/cm³) and the leakage of electrostatic charge from PE film were measured. PolyNIPAAm that was introduced onto PE surface has hydrophilic-hydrophobic transition properties at the 32°C in the atmospheric condition. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1773–1779, 1998     

Photopolymerization synthesis of poly(N-isopropylacrylamide) hydrogels

Poly(N-isopropylacrylamide) (NIPAAm) gels were formed by photopolymerization of NIPAAm in the absence of a crosslinker using a water solvent at 25°C. Factors affecting formation were the wavelength region of irradiated light, the type of photoinitiators, and the concentrations of the photoinitiator and monomer. A high-pressure mercury lamp (400 W) was used as a light source. An NIPAAm concentration of 10 wt % and irradiation time of 15 h was used for the photopolymerization. The gel (68% yield) was formed when the quartz glass system was used, but no gelation was observed for the Pyrex glass system that transmits light with π > 290 nm. The gel (100% yield) was easily formed, even in the latter system, when 30 mmol/L of hydrogen peroxide and potassium persulfate were used as the photoinitiator. Water soluble photoinitiators such as ferric chloride and sodium anthraquinone-2,7-disulfonate were not effective for the gel formation. Yield of the gel increased with increasing the potassium persulfate concentration (1–30 mmol/L), but it decreased when a high concentration of hydrogen peroxide (60 mmol/L) was used. The gel yield increased with the NIPAAm concentration (5–20 wt %). The degree of swelling of the resultant poly(NIPAAm) gels, which was measured by immersing the gels in water at various temperatures (0–50°C) for 24 h, steeply decreased at about 30°C with increasing temperature, exhibiting a temperature-responsive character. The gels swelled and shrank in water below and above the temperature, respectively. The extent of the character depended on the concentrations of hydrogen peroxide and monomer. The formation mechanism of the gel in the photopolymerization of NIPAAm using hydrogen peroxide photoinitiator was discussed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1313–1318, 1997     

Interpolymer complexes of poly(acrylamide) and poly(N-isopropylacrylamide) with poly(acrylic acid): a comparative study

The interpolymer complexation, through successive hydrogen bonding, between poly(acrylamide) (PAAm) and poly(N-isopropylacrylamide) (PNiPAAm) with poly(acrylic acid) (PAA) in aqueous solution has been viscometrically and potentiometrically investigated. The stoichiometry of the complexes formed was determined. By comparing the strength of the two complexes the very important contribution of the hydrophobic interaction in their formation has been indicated.     

Poly(N-vinylpyrrolidone)-grafted poly(N-isopropylacrylamide) copolymers: Synthesis, characterization and rapid deswelling and reswelling behavior of hydrogels

Poly(N-isopropylacrylamide)-block-poly(N-vinylpyrrolidone) diblock copolymer (PNIPAAm-b-PVPy) was successfully synthesized via sequential reversible addition-fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) process, in which the chain transfer agent of xanthate was in situ afforded via the reaction of isopropylxanthic disulfide (DIP) with 2,2-azobisisobutylnitrile (AIBN). The RAFT/MADIX technique was employed to prepare the poly(N-vinylpyrrolidone)-grafted poly(N-isopropylacrylamide) copolymers (PNIPAAm-g-PVPy) with N,N-methylenebisacrylamide as the crosslinking agent. The comb-like PNIPAAm-g-PVPy copolymer networks with PVPy as the pendent chains were characterized by means of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS). The hydrogel behavior of PNIPAAm-g-PVPy networks was investigated in terms of swelling, deswelling and reswelling tests. With the inclusion of PVPy chains, the swelling ratios of the hydrogels were significantly enhanced compared to the control PNIPAAm hydrogel. It is found that the PVPy-modified PNIPAAm hydrogels displayed faster response to the external temperature changes than the control PNIPAAm hydrogel. The improved thermoresponsive properties of hydrogels are ascribed to the formation of the comb-like architectures in the copolymer networks.     

温敏性聚(N-异丙基丙烯酰胺)/聚丙烯酰胺互穿网络水凝胶

采用紫外引发法制备了物理交联的聚(N-异丙基丙烯酰胺)和化学交联聚丙烯酰胺为组分的互穿网络水凝胶。利用FFIR对所得的凝胶进行了结构分析;测定了该水凝胶在20℃时的溶胀率和50℃时的水保持率;利用DMA和DSC分别研究了水凝胶的储能模量随温度的变化及相转变行为。结果表明:与聚(N-异丙基丙烯酰胺)水凝胶相比,该水凝胶有较好的溶胀率;且具有超快的响应速率,如10 min内失去90%的水;其储能模量增加;虽然其相转变行为变弱,但临界溶解温度(LCST)有所提高。     

Thermal characterization of poly(vinyl chloride) samples prepared by living radical polymerization: Comparison with poly(vinyl chloride) prepared by free radical polymerization

Poly(vinyl chloride) (PVC) samples were synthesized by a living radical polymerization (LRP) method and compared with commercial PVC prepared by the conventional free radical polymerization (FRP). The differences were assessed, for the first time, in terms of viscosimetry parameters and thermal analysis. The LRP method used to prepare the PVC‐LRP samples is the only one available to obtain this polymer free of structural defects, being of commercial interest in a view of preparing a new generation of PVC‐based polymer with outstanding performance. The polymerization temperature selected (35°C) to prepare the LRP samples is currently used in the industry to prepare PVC‐FRP grades with moderate to high molecular weight. Since the thermal stability is a direct consequence of the polymer structure, this study is of vital importance to understand the potential of new PVC‐LRP. The thermoanalytical measurements demonstrate an enhanced thermal stability of PVC‐LRP when compared with its FRP counterpart. The PVC‐LRP sample with very low molecular weight reveals a higher thermal stability than the most stable PVC‐FRP sample. It is the first report dealing with thermal analysis of PVC prepared by LRP. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008