含自由氨基酸侧链的温敏性微凝胶的制备及性能

采用无皂乳液聚合法使N-异丙基丙烯酰胺(NIPAM)、ε-丙烯酰基-L-赖氨酸(εACRLLY)和N,N-亚甲基双丙烯酰胺(BA)交联共聚,制备了含有自由氨基酸侧链的温敏性微凝胶.利用透射电子显微技术(TEM)、动态光散射技术(DLS)及浊度法对所制备的微凝胶的形态及相转变进行了表征.TEM结果表明,所得的微凝胶具有规则的球型形态,微凝胶的粒径随εACRLLY含量的增加而减小.DLS及浊度结果表明,微凝胶粒径呈单分散的窄分布,随着温度的升高,微凝胶粒径减小,有着明显的体积相转变温度(VPTT);亲水单体εACRLLY的引入能够有效地调节共聚物微凝胶的VPTT,并且VPTT随εACRLLY含量的增加几乎呈线性上升.微凝胶在对盐酸阿霉素的药物释放研究表明,所制备的微凝胶在20℃,12 h内释放了56%,37℃下释放了73%;37℃,pH=7.4下13 h内释放73%,pH=4.5下基本释放完毕,该微凝胶表现出良好的药物缓释性能.     

葡萄糖敏感微凝胶的溶胀动力学研究

通过沉淀聚合法合成了P(NIPAM-co-AA)微凝胶,然后在EDC催化下用3-氨基苯硼酸对微凝胶进行改性,制备了P(NIPAMI-co-AAPBA)微凝胶.红外光谱检测证明改性完全.改性后的微凝胶仍具有很好的温敏性,但由于引入疏水的苯硼酸基团,微凝胶的体积相转变温度大大降低.P(NIPAM-co-AAPBA)微凝胶具...     

温度、pH敏感性核壳结构微凝胶的制备及性质

以无皂乳液分步聚合的方法, 将N-异丙基丙烯酰胺(NIPAM)与N,N-亚甲基双丙烯酰胺(MBA)交联反应3 h, 制得种子乳液, 再向种子乳液中加入甲基丙烯酸(MAA)功能性单体继续反应2 h, 制备了具有温度、pH敏感性的核壳结构微凝胶. 通过透射电子显微镜(TEM)、红外光谱(IR)等表征了微凝胶外貌形态及结构组成, 动态光散射(DLS)测定了微凝胶粒径响应热、pH的变化及微凝胶Zeta电位的变化. 结果表明凝胶形貌为异型核壳结构; Zeta电位与微凝胶粒径随温度、pH变化相关.     

反相微乳液聚合法制备聚(丙烯酰胺-co-丙烯酸)pH敏感微凝胶及其性能

以丙烯酰胺(AM)和丙烯酸(AA)单体的水溶液为分散相,失水山梨醇单油酸脂(Span80)/聚氧乙烯失水山梨醇脂肪酸脂(Tween80)/异辛烷为分散介质,分别以N,N′-亚甲基双丙烯酰胺(MBA)、过硫酸铵/亚硫酸氢钠((NH4)2S2O8/NaHSO3)为交联剂和氧化还原引发剂,在30℃进行反相微乳液聚合制备了一系列不同单体摩尔百分数的P(AM-co-AA)微凝胶.通过傅立叶红外光谱、浊度法、透射电镜(TEM)和动态光散射(DLS)等测试手段分别对微凝胶特征官能团的存在、pH敏感性、微观形态、粒径大小及粒径分布等进行表征分析.结果表明,共聚物中存在AM和AA结构单元;样品的TEM照片显示在原料中AA的摩尔百分数为60%时,P(AM-co-AA)微凝胶粒子的数均粒径为90 nm左右,呈现非规则球形;DLS结果表明,P(AM-co-AA)微凝胶与PAM微凝胶相比具有较宽的粒径分布,且随原料中AA摩尔百分数增加,粒径分布逐渐变宽;P(AM-co-AA)微凝胶具有良好的pH敏感性,敏感pH值与AA的解离常数有关,通过调节pH值可以迅速控制自身体积的溶胀与收缩.     

含β-CD单元VCL共聚物微凝胶的合成与性能研究

采用无皂沉淀聚合法,在水溶液中通过N-乙烯基己内酰胺(VCL)与一种单取代乙烯基β-环糊精单体(GMA-EDA-β-CD)的共聚反应,合成出了含有β-CD结构单元的温敏性VCL/GMA-EDA-β-CD共聚物微凝胶.用红外光谱仪(FTIR)、1H核磁共振仪(1H-NMR)、透射电镜(TEM)及激光粒度仪(DLS)对其结构、形态和性能进行了表征.研究结果表明,β-CD结构单元的加入使共聚物微凝胶的粒径减小,粒径分布变窄,但其温敏性降低.     

线形苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)的粘弹弛豫与相形态

研究了不同温度下苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)的粘弹弛豫与相形态. DSC分析发现, SBS的相结构特别是其中质量分数较低的PS相畴的大小受热历史影响显著. 用TEM表征了SBS的双相连续形态和两相相畴尺寸. 用动态流变学方法研究了不同温度下SBS嵌段大分子的松弛行为. 结果表明, 在低于PS相玻璃化转变温度时, 嵌段分子中的PB段已可发生运动; 而当高于PS玻璃化转变温度后, 由于PB与PS间的相互作用及PB的链缠结所限制, 体系仍保持较高的弹性模量, 呈现“第二平台”特征流变行为.     

pH响应性阳离子型微凝胶的制备及性质研究

以甲基丙烯酸-(N,N-二甲氨基)乙酯(DMAEMA)和丙烯酸乙酯(EA)为共聚单体, 二甲基丙烯酸乙二醇酯(EGDMA)为交联剂, 采用半连续乳液聚合法, 制备了具有pH响应性的阳离子型微凝胶, 并研究不同聚合条件对所合成的微凝胶性质的影响. 利用透射电子显微镜(TEM)、激光粒度分析仪和流变仪对微凝胶进行一系列表征. 研究了介质pH值对微凝胶的形态、平均粒径、zeta电位、溶液浊度(透光率)的影响, 以及NaCl盐溶液对微凝胶分散体系稳定性的影响. 结果表明, 这类阳离子型微凝胶体系具有良好的pH响应性, 在pH＝7左右发生相转变. 此外, 研究表明不同浓度NaCl溶液对微凝胶的稳定性有一定影响, 临界絮凝浓度约为1.3 mol•L－1.     

水分子凝胶聚集态的DSC和AFM研究

合成了一种新型凝胶因子，能在很低的浓度下使水发生凝胶化，形成水分子凝 胶。通过原子力显微镜(AFM)以及透射电子显微镜(TEM)对水分子凝胶的微观形态进 行了表征，表明凝胶因子可以在水中聚集、自组装成延伸的螺旋缠绕细纤维结构， 并且得出了纤维束的平均直径在100nm左右，平均孔径在100nm左右。利用示差扫描 量热(DSC)的数据，计算了水分子凝胶体系的平均孔径大小在50～100nm左右，与 AFM和TEM观测的结果较吻合，从而验证了DSC理论推导计算的正确性。同时还得到 了不同浓度的水分子凝胶的凝胶—溶胶相转变温度Tcs在55—72℃之间，而且随着 凝胶因子浓度的增加，水分子凝胶体系的平均孔径呈减小的趋势，凝胶—溶胶相转 变温度呈上升的趋势。     

pH响应性阳离子微凝胶-纳米Pd催化剂的制备及性能

以聚乙二醇甲基丙烯酸酯(PEGMA)为大分子稳定剂,通过乳液聚合制备稳定性良好的具有pH响应性聚甲基丙烯酸二乙基氨基乙酯(PDEA)微凝胶,以其为模板将一定量的四氯钯酸钠(Na2PdCl4)溶液通过静电作用充分络合到高分子微凝胶的网络结构中,并以NaBH4为还原剂,原位合成法制备pH响应性阳离子微凝胶-纳米Pd催化剂.利用透射电镜(TEM)、动态光散射(DLS)、紫外-可见分光光度计(UV-Vis)、热重分析(TGA)和X射线衍射仪(XRD)分别对阳离子微凝胶-纳米Pd催化剂的形貌、pH响应性、静电力、Pd负载量和Pd晶型进行了表征及分析.结果表明,制备得到的纳米Pd的平均粒径约为3.5 nm;紫外吸收光谱图中,PDEA-Na2PdCl4复合体系在波长280 nm出现吸收峰,证明PdCl42-与微凝胶之间存在相互作用力;pH响应性阳离子微凝胶-纳米Pd催化剂还原4-硝基苯酚具有很好的催化活性,其催化活性与微凝胶网络的pH响应性有一定关系.此外对阳离子微凝胶-纳米Pd催化剂循环使用的状况进行了初步研究.     

阳离子化热响应微凝胶的合成及在二氧化硅矿化中的应用

采用无皂乳液聚合技术,在亚甲基双丙烯酰胺(MBA)为交联剂的情况下,N-异丙基丙烯酰胺(NIPAM)与甲基丙烯酰氧乙基三甲基氯化铵(DMC)发生共聚,生成具有阳离子功能化的热响应微凝胶poly-(NIPAM-co-DMC).TEM研究表明该微凝胶粒子的粒径约为200 nm左右,具有规则的球形形态.DLS和1H-NMR研究证实了微凝胶粒子的最低临界溶液温度(LCST)在34℃左右.进一步以此微凝胶为模板,在中性条件下,以四甲氧基硅烷(TMOS)为硅源,在此模板上仿生沉积S iO2,生成poly(NIPAM-co-DMC)/S iO2杂化纳米粒子.FTIR、TEM、1H-NMR及TGA等研究表明S iO2在聚合物模板上发生了沉积.能谱分析进一步证明了S iO2主要分布在杂化纳米粒子的壳层区域.另外,当矿化反应温度高于微凝胶的LCST值时,体系生成了具有明显核壳结构的异形杂化粒子.     

Deswelling comparison of temperature‐sensitive poly(N‐isopropylacrylamide) microgels containing functional ?OH groups with different hydrophilic long side chains

Two monomers containing functional ? OH groups with different hydrophilic long side chains (viz., triethyleneglycol methacrylate (TREGMA) and polyethyleneglycol methacrylate (PEGMA)) were selected to modify the swelling/deswelling behavior of poly(N‐isopropylacrylamide) (pNIPAM) microgels. Dynamic scattering technique, turbidimetric method, and differential scanning calorimetry (DSC) were employed to investigate the deswelling behavior of the microgels. Experimental results show that the two series of microgels are identical in that incorporation of hydrophilic chains containing ? OH groups causes the volume‐phase transition temperature (VPTT) of pNIPAM microgels to shift to higher temperature; the more hydrophilic the side chains, the more the VPTTs shift. Although PEGMA are more effective in elevating the VPTTs of pNIPAM microgels than TREGMA, p(NIPAM‐co‐TREGMA) microgels show better deswelling properties than p(NIPAM‐co‐PEGMA) microgels, i.e., they have much larger deswelling ratios (α) and display less continuous volume‐phase transition. The VPTTs of the modified microgels can be modulated to well close to the normal body temperature of human beings. These characteristics along with the functional ? OH groups they contain make the microgels competitive candidates for biomaterials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3575–3583, 2005     

Different deswelling behavior of temperature-sensitive microgels of poly(N-isopropylacrylamide) crosslinked by polyethyleneglycol dimethacrylates

Polymerization of N-isopropylacrylamide (NIPAM) with polyethyleneglycol dimethacrylates (n G, n representing the number of --CH2CH2O-- units in polyethyleneglycol dimethacrylates) through surfactant-free radical polymerization was used to prepare the temperature-sensitive microgels. The morphology, dispersity, and deswelling behavior of the microgels were investigated by means of transmission electron microscopy (TEM), ultraviolet-visible spectroscopy, differential scanning calorimetry (DSC), and dynamic light scattering (DLS) techniques. TEM micrographs revealed that it was feasible to obtain regular spherical microgels for crosslinking agents with short chain. Turbidity, DSC, and DLS analysis showed that in marked contrast to 1G and 3G crosslinked microgels, the collapse of microgels crosslinked by 9G, 14G, and 23G proceeded in a two-step mechanism. The amide groups dehydrated at the lower temperature leading to the first-step transition. In the transition, the hydrophilic long --(--CH2CH2O--)n-- segments could be enriched on the surface of the microgels, which was further verified by variable temperature 1H NMR spectroscopy. The hydrophilic long --(--CH2CH2O--)n-- segments can be dehydrated at the higher temperature.     

Effects of hectorite content on the temperature-sensitivity of PNIPAM microgels

A new method, adopting inorganic clay (synthetic hectorite) as a physical cross-linker, was used to prepare poly(N-isopropylacrylamide) (PNIPAM) microgels via surfactant-free emulsion polymerization. The effect of hectorite content on the temperature-sensitivity of PNIPAM microgels was investigated by means of DLS, UV/Vis and DSC. It was found that, in the absence of surfactant, with increasing hectorite content, the particle size tends to decrease to 300 nm at room temperature, while increases as weight ratio (WR) of hectorite and N-isopropylacrylamide (NIPAM) exceeds 21%. Furthermore, with increasing WR from 7% to 21%, the volume phase transition temperature of PNIPAM microgels has little shift, while decreases slightly when WR increases up to 28%.     

Effects of addition of anionic and cationic surfactants to poly(N-isopropylacrylamide) microgels with and without acrylic acid groups

The interaction of the anionic surfactant sodium dodecyl sulfate (SDS) and the cationic surfactant hexadecyl trimethyl ammonium bromide with poly(N-isopropylacrylamide) (PNIPAAM) microgels with and without poly(acrylic acid) (PAA) was investigated by means of dynamic light scattering (DLS), zeta potential, and turbidimetry measurements. The DLS results show that the PNIPAAM microgels with PAA will contract when an anionic or cationic surfactant is added to the suspension, while the PNIPAAM microgels without PAA expand in the presence of an ionic surfactant. A collapse of the PNIPAAM microgels is observed when the temperature is increased. From the zeta potential measurements, it is observed that the charge density of PNIPAAM microgels in the presence of an ionic surfactant is significantly affected by temperature and the attachment of the negatively charged PAA groups. The turbidity measurements clearly indicate that the interaction between PNIPAAM and SDS is more pronounced than that of the cationic surfactant.     

磁性凹凸棒土温敏性微凝胶的合成及其体外实验

通过乳液聚合法制备了叶酸(FA)接枝的磁性FA-Fe3O4/凹凸棒土-聚(N-异丙基丙烯酰胺-丙烯酰胺)(FA-Fe3O4/ATP-P(NIPAM-AAM))复合微凝胶(凹凸棒土=ATP,N-异丙基丙烯酰胺=NIPAM,丙烯酰胺=AAM),并通过X射线衍射(XRD)、振动样品磁强计(VSM)、热重(TG)、红外分析(I...     

Composite structure of temperature sensitive chitosan microgel and anomalous behavior in alcohol solutions

Poly(N-isopropylacrylamide)/chitosan (PNIPAM/CS) core-shell microgel was synthesized by graft copolymerization. The microstructure of copolymers was characterized by FT-IR spectrum and (1)H-nuclear magnetic resonance ((1)H NMR). Transmission electron microscope (TEM) and dynamic light scattering (DLS) measurements display that the microgel has high monodispersity and with a core-shell structure. For swelling the microgel in various alcohol solutions, the particles first shrink; then flocculation occurs resulted from weak aggregation of particles with the increase of alcohol concentration. The investigation of the size of microgels as a function of temperature shows that the thermo-sensitive property is markedly exhibited when the alcohol concentration is low, and vanishes when the alcohol concentration exceeds some value where the microgels have the lowest size.