PNI PAM/CS微凝胶的性质测定

以N-异丙基丙烯酰胺(NIPAM)、壳聚糖(CS)为单体,N,N-亚甲基双丙烯酰胺(MBA)为交联剂,制备了PNIPAM/CS微凝胶.测定了不同单体配比对微凝胶体积相转变温度(VPTT)的影响和25℃不同pH条件下微凝胶液浊度及粒径的变化.研究表明,PNIPAM/CS微凝胶具有温敏性;并且随着pH的增大,微凝胶粒径先变小后变大,显示pH敏感性;浊度法测定结果与粒径测定一致.     

浊度法表征温敏性微凝胶体积的相转变行为

以N-异丙基丙烯酰胺(NIPAM)、甲基丙烯酸(MAA)为单体,N,N-亚甲基双丙烯酰胺(MBA)为交联剂,制备了温敏性聚(N-异丙基丙烯酰胺)(PNIPAM)和具有温度、pH敏感性的聚(N-异丙基丙烯酰胺-co-甲基丙烯酸)(PNIPAM-MAA)微凝胶。通过测定不同温度和pH条件下微凝胶浊度变化,表征微凝胶的温度及pH敏感性,描述了NaCl浓度和pH对微凝胶体积相转变温度的影响。同时,测定了微凝胶的临界聚沉浓度及临界絮凝温度,表征了微凝胶的稳定性,讨论了影响微凝胶的稳定性因素。     

快速响应的温敏性聚(N-异丙基丙烯酰胺)水凝胶的合成及表征

快速响应的温敏性聚(N-异丙基丙烯酰胺)水凝胶的合成及表征;N-异丙基丙烯酰胺;水凝胶;温敏性;快速响应     

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...     

磁性半互穿网络智能水凝胶的合成及性质评价

以甲基丙烯酸(MAA)、N-异丙基丙烯酰胺(NIPAAm)、丙烯酰胺(AM)为原料,N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,利用IPN技术并结合磁性的γ-Fe2O3增强剂,在水溶液中制备了半互穿网络水凝胶(PMAA/PAM-NIPAAm/γ-Fe2O3),研究了水凝胶的溶胀性﹑热稳定性和电磁性。实验表明,水凝胶形成稳定的IPN互穿网络结构且该水凝胶具温度、pH双重敏感性和顺电磁性。所合成的水凝胶在低临界溶解温度31℃以下,具有明显正向温敏性,高于此温度,水凝胶的温度敏感性会逐渐减弱。产品成功克服了NIPAAm类水凝胶的温缩性。     

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.     

粘土对N-异丙基丙烯酰胺和丙烯酸叔丁酯共聚形成微凝胶的影响

以无机粘土(锂蒙脱石)作为物理交联剂,在不加任何乳化剂的条件下,通过无皂乳液聚合制备了一系列粒径在250nm左右且具有温敏性的N-异丙基丙烯酰胺(NIPAM)和丙烯酸叔丁酯(tBA)共聚微凝胶,并通过傅立叶变换红外光谱、扫描电镜、准静态光散射、X射线衍射仪和差示扫描量热法对所合成微凝胶的化学结构、表面形态和温度敏感性进行了表征.研究表明,粘土起到交联剂的作用;tBA的引入可以调节微凝胶的体积相转变温度;所制得的粘土交联微凝胶具有较好的粒径分布且粒径在140nm至350nm之间.     

结构型载体负载纳米银合成及催化性能

通过两步聚合法合成具有温度敏感性能的核-壳型聚(苯乙烯-N-异丙基丙烯酰胺)/N-异丙基丙烯酰胺共聚3-(甲基丙烯酰氧)丙基三甲氧基硅烷(P(St-NIPAM)/P(NIPAM-co-MPTMS))复合微凝胶材料.以经3-巯丙基-三甲氧基硅烷(MPS)表面修饰的复合微凝胶为载体,乙醇为还原剂,在温和条件下控制性还原制备纳米银微粒.通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶变换红外(FT-IR)光谱仪、X-射线光电子能谱(XPS)、X射线衍射(XRD)仪、热分析(TGA)和紫外-可见(UV-Vis)分光光度计等手段对P(St-NIPAM)/P(NIPAM-co-MPTMS)-(SH)Ag复合微凝胶的结构、组成和性质进行表征.同时,以硼氢化钠还原对硝基苯酚为模型反应,对该复合材料催化还原性能进行了评价.结果表明,载体含有巯基的有机-无机杂化网络结构的限域作用使原位合成的纳米银微粒的分散性较好.载体微凝胶壳层链节中无机组分MPTMS的引入在一定程度上降低了复合凝胶温敏性,但复合凝胶仍表现出催化还原反应的温敏性调控和良好的催化活性.以上实验结果与温敏性PNIPAM链节被无机网络分隔而有利于反应传质及壳层巯基对原位纳米银形成尺寸和空间分布的有效控制有关.本研究对功能性金属纳米催化复合材料的研究具有积极借鉴意义.     

明胶-聚异丙基丙烯酰胺水凝胶的pH、温度敏感性

用明胶(Gel)和N 异丙基丙烯酰胺(NIPAM)为原料,制备了Gel/聚异丙基丙烯酰胺(PNIPAM)水凝胶;研究了不同含量的水凝胶的温度、pH敏感性。结果表明:温度对水凝胶pH敏感性的影响取决于水凝胶的组成。明胶含量高的水凝胶,其pH敏感性几乎不受温度的影响;当0.500.90时,pH值几乎不影响水凝胶的温敏性。     

温度及pH敏感N-异丙基丙烯酰胺/β-环糊精水凝胶的合成与性能研究

用顺丁烯二酸酐 (MAH)对具有分子包结能力的 β 环糊精 (β CD)进行化学改性 ,合成出了丁烯二酸单酯化 β CD单体 (MAH β CD) .通过氧化还原自由基引发MAH β CD与N 异丙基丙烯酰胺 (NIPA)聚合 ,合成出含 β CD结构单元的新型水凝胶 .用核磁共振、红外光谱及元素分析对MAH β CD单体及共聚物的结构和组成进行了表征 .溶胀研究结果表明 ,该水凝胶具有较好的pH、温度及离子强度敏感性 ;并且水凝胶在较高羧基(—COOH)含量和弱碱环境中 ,仍能表现出明显的温敏性     

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     

Flocculation behavior of temperature-sensitive poly(N-isopropylacrylamide) microgels containing polar side chains with -OH groups

The flocculation behavior of poly(N-isopropylacrylamide) (pNIPAM) microgels containing polar -(OCH(2)CH(2))(3)OH chains, incorporated by the copolymeric components (triethyleneglycol methacrylate, TREGMA), in aqueous NaCl solution was investigated. Determination of the critical flocculation temperatures (CFTs) and the critical flocculation concentrations (CFCs) of the microgels at 45 degrees C shows that polar -(OCH(2)CH(2))(3)OH chains have different influence on the flocculation behavior of the microgels at temperatures below and above their volume phase transition temperatures (VPTTs). The flocculation of the microgels becomes more difficult with the increase of -(OCH(2)CH(2))(3)OH chains below the VPTT. In contrast, the microgels flocculate more easily with more -(OCH(2)CH(2))(3)OH chains above the VPTT. Preliminary investigation on the flocculation kinetics of the microgels further shows that -(OCH(2)CH(2))(3)OH chains have different effects on the flocculation rate at temperatures below and above the VPTT. The flocculating rate of the microgels at 25 degrees C decreases with the increase of -(OCH(2)CH(2))(3)OH chains. While the flocculation rate at 45 degrees C increases with the increase of -(OCH(2)CH(2))(3)OH chains due to their enrichment on the surface of the microgels as a result of the temperature-induced volume-phase transition, which was verified by variable temperature (1)H NMR spectroscopy. The polar -(OCH(2)CH(2))(3)OH chains rich in the surface increase the attractive force between the microgels, promoting the flocculation.     

变温反相悬浮聚合制备温度敏感性聚合物微凝胶

报道了一种利用变温的途径制备具有温度敏感性聚合物凝胶微粒的悬浮聚合方法.以正庚烷为连续相,过硫酸铵和四甲基乙二胺为引发剂,采用将具有反向温敏性的可降解大分子单体水溶液在低温下分散好以后再升高到聚合温度的变温反相悬浮聚合的方法制备了反向温敏性的可降解微凝胶.该方法避免了由于分散相在聚合温度下发生物理凝胶化所导致的分散困难等问题.考察了微凝胶的温敏性、粒径分布和降解行为等,并研究了油水比对微凝胶形貌的影响.     

基于互穿网络结构的pH/温度双重刺激响应性微凝胶的研究

室温下采用氧化-还原引发体系,以低交联密度的聚(N-异丙基丙烯酰胺)(PNIPAM)微凝胶为种子,通过种子乳液聚合法合成由PNIPAM和聚丙烯酸(PAA)形成的具有互穿聚合物网络结构的微凝胶.傅立叶变换红外光谱分析结果表明微凝胶由PNIPAM和PAA两种聚合物组成,透射电镜表征结果证实微凝胶中PNIPAM和PAA两种聚合物形成了互穿网络结构.用动态激光光散射测试不同温度或pH值水介质中微凝胶的粒径,结果发现微凝胶具有良好的pH/温度双重刺激响应性.在水介质pH值大于5.5的情况下,PAA组分对微凝胶的体积相转变温度没有影响;而在水介质pH值为4.0的情况下,由于PAA与PNIPAM之间的氢键作用,微凝胶的体积相转变温度稍微降低.微凝胶中PAA组分含量越高,其pH刺激响应性越显著.     

Control of poly(N-isopropylacrylamide) microgel network structure by precipitation polymerization near the lower critical solution temperature

Poly(N-isopropylacrylamide) (pNIPAm) microgels were synthesized by precipitation polymerization at temperatures ranging from 37 to 45 °C using redox initiator system ammonium persulfate (APS)/N,N,N',N'-tetramethylethylenediamine (TEMED) or photoinitiator 2,2'-azobis(amidinopropane) dihydrochloride (V50). Photon correlation spectroscopy (PCS) and atomic force microscopy (AFM) studies revealed that spherical microgels with narrow size dispersities can be obtained with these methods and that the resultant microgels have volume phase transition behaviors expected from their compositions. Additionally, the low-temperature redox initiator strategy produces microgels devoid of self-cross-linking, thereby permitting the synthesis of completely degradable microgels when using N,N'-(1,2-dihydroxyethylene)bisacrylamide (DHEA) as a cleavable cross-linker. We also demonstrate the potential utility of the approach in bioconjugate syntheses; in this case, avidin immobilization is demonstrated by one-pot copolymerization at low temperature.     

Thermodynamic considerations of microgel swelling behavior

A simple but novel thermodynamic model is presented, based upon van't Hoff analysis, for the reversible swelling behavior of colloidal microgels. The swelling, as a function of temperature, of poly(N-isopropylacrylamide/N,N'-methylenebisacrylamide) as well as poly(N-isopropylacrylamide/vinylpyridine/N,N'-methylenebisacrylamide) and poly(N-isopropylacrylamide/acrylic acid/N,N'-methylenebisacrylamide) microgel dispersions in H2O and D2O has been studied by photon correlation spectroscopy (PCS). PCS data was used to obtain the hydrodynamic diameter and hence the volume of the microgels (before and after reconstitution following freeze-drying) as a function of temperature. The choice of standard reference states, for analyzing the data attained, is discussed, and the one selected is that of the volume of the microgels at 333 K in H2O. For all microgels examined the volume, at this temperature, is shown to be independent of solvent (H2O, D2O). The derived data has allowed the exploration of a novel thermodynamic approach to the study of the swelling behavior of the microgels. The constant volume, at 333 K, for each of the polymer systems constituting the microgels is suggested to be an intrinsic property of the polymers themselves.     

Preparing and physicochemical properties of microcrystalline polyacrylic acid gels

The facile synthesis of microcrystalline polyacrylic acid (PAA) gels via emulsion polymerization is presented and the effects of experimental factors that determine the microcrystallization of PAA microgels were investigated. Both reaction temperature and emulsifier type play important roles in the crystallization of PAA microgels. Selected-area electron diffraction and X-ray diffraction patterns show that the PAA microgels formed using sodium dodecyl sulfate as emulsifier are single-crystallized, and low reaction temperature favors the formation of the PAA microgels with high crystallinity. Controlling the reaction temperature may also improve morphology controllability by emulsion polymerization in synthesizing microcrystalline PAA gels. In addition, the microcrystalline PAA gels exhibit good Young’s modulus, which is 7.8 times higher than that of the PAA microgels.     

Assembly of Preformed Gold Nanoparticles onto Thermoresponsive Poly(N‐isopropylacrylamide)‐Based Microgels on the Basis of Au‐thiol Chemistry

The assembly of preformed gold nanoparticles (AuNPs ) onto the thermoresponsive poly(N ‐isopropylacrylamide) (PNIPAM )‐based microgels was achieved on the basis of the driving force of Au‐thiol chemistry. The loading amount of AuNPs can be controlled by varying the ratio of AuNPs relative to PNIPAM ‐based microgels. The as‐prepared PNIPAM /Au hybrid microgels showed well‐defined reversible swelling/deswelling transition in response to temperature, which can be employed to tune the plasmonic property of hybrid microgels. As the temperature was increased, the position of localized surface plasmon resonance (LSPR ) band red‐shifted to some extent mainly due to the increase in the local refractive index around AuNPs .     

Effect of chemical composition on properties of pH-responsive poly(acrylamide-co-acrylic acid) microgels prepared by inverse microemulsion polymerization

In this research, a series of pH-responsive microgels based on acrylamide (AM), acrylic acid (AA) as the main monomers, and N,N′-methylenebisacrylamide as a divinyl cross-linking agent, have been prepared by inverse microemulsion polymerization. The effect of chemical composition of poly(acrylamide-co-acrylic acid) (P(AM-co-AA)) on hydrodynamic diameters, morphology, swelling ratios and pH-responsive behaviour and thermal properties of microgels were discussed. With an increase of the mole percentages of AA in the feed ratio, the microgels have higher swelling ratios. The TEM photographs show that the spherical morphology of the microgels are regular relatively. Comparing with PAM microgels, number-average diameters of P(AM-co-AA) microgels were larger because of the presence of AA chain segment in the polymer chain. Turbidities of microgels determined through UV–vis spectrophotometer indicate that the microgels exhibit favourable pH-responsive behaviour, and responsive pH value is related to the dissociation constant of AA. Moreover, thermal stable properties of microgels were confirmed by differential scanning calorimeter. It was observed that an increase in the mole percentages of AA in the feed ratio provided lower glass transition temperature and thermal decomposition temperature of pH-responsive microgels.     

Preparation and characterization of novel cationic pH-responsive poly(N,N'-dimethylamino ethyl methacrylate) microgels

Novel monodisperse cationic pH-responsive microgels were successfully prepared by dispersion polymerization in ethanol/water mixture using N,N'-dimethylamino ethyl methacrylate (DMAEMA) as the monomer, poly(vinyl pyrrolidone) (PVP) as the steric stabilizer and N,N'-methylenebisacrylamide (MBA) as the cross-linker. The effects of various polymerization parameters, such as medium polarity, concentration of cross-linker, concentration of monomer, and concentration and molecular weight of stabilizer on the final diameter and monodispersity of poly(N,N'-dimethylamino ethyl methacrylate) (PDMAEMA) microgels were systematically studied. The pH-responsive characteristics of PDMAEMA microgels were also investigated. The experimental results showed that these microgels exhibited excellent pH-responsivity and significantly swelled at low pH values. The maximum ratio of volume change of the prepared microgels in response to pH variation was more than 11 times. It was found that the prepared microgels completely aggregated at the isoelectric point (IEP) around pH 6. On the other hand, the microgels were stable in aqueous solution at both low and high pH values. The results can be used for effectively controlled separation of particles.