ATRP法制备环境响应型智能膜材料的研究进展

聚（N-异丙基丙烯酰胺）（PNIPAM）作为一种常见的智能材料,同时具有温度响应特性和乙醇浓度响应特性。本文以PNIPAM聚合物为主线,着重介绍了利用原子转移自由基聚合（ATRP）法制备温度响应型、温度及pH值双重响应型、乙醇浓度响应型智能膜材料的研究成果。其中,温度响应型智能膜主要介绍PNIPAM均聚物接枝膜;温度及pH值双重响应型智能膜主要介绍PNIPAM与pH值响应型聚合物的嵌段接枝膜;乙醇浓度响应型智能膜主要介绍PNIPAM无规共聚物接枝膜。另外,还介绍了其它响应型智能膜,包括手性分子及离子响应型接枝膜的研究成果。基于ATRP法在文中所述的优点以及在膜改性研究方面的广泛应用,相信该方法在制备环境响应型智能膜材料以及推动智能膜实际工业应用方面将扮演重要角色。     

温度感应式开关膜的接枝率对其开关特性的影响

利用等离子体诱导填孔接枝聚合法将聚(N-异丙基丙烯酰胺)（PNIPAM）接枝聚合在聚偏氟乙烯（PVDF）微孔膜上制备了一系列具有较宽接枝率范围的温度感应式开关膜,系统地研究了接枝率对膜的温度感应开关特性的影响.结果表明,开关膜的接枝率对膜的过滤通量、温度感应开关系数和膜孔径感温变化倍数都有十分重要的影响.接枝率在小于等于2.81%时,温度感应开关系数和膜孔径感温变化倍数均随接枝率增加而增加;而对于接枝率大于等于6.38%的膜,膜开关系数和膜孔径感温变化倍数总是趋近于1,膜不具备温度感应开关特性.为了获得预期的开关性能,必须将膜的接枝率控制在适当的范围.     

双响应性嵌段聚合物的纳米孔开关效应的计算机模拟

利用计算机模拟方法 (耗散粒子动力学)研究了双响应性嵌段聚合物修饰的纳米孔的开关效应。通过在纳米孔内接枝具有温度和pH响应的嵌段聚合物(N-异丙基丙烯酰胺和丙烯酸),研究不同嵌段序列(即wall-PNIPAM-PAA或wall-PAA-PNIPAM)对纳米孔开关效应的影响,结果表明,只有wall-PNIPAM-PAA嵌段序列可以实现纳米孔在不同条件下的开关效应。同时还探究了接枝密度、链长和嵌段比例对纳米孔开关效应的影响,结果表明,中高等接枝密度、适合的链长和中等比例的嵌段比可以实现不同特征的纳米孔,用于控制纳米孔的开关效应。     

采用ATRP反应合成嵌段共聚物P(n-BMA-b-NIPAM)的研究

采用原子转移自由基聚合(ATRP)反应合成了甲基丙烯酸正丁酯/N-异丙基丙烯酰胺嵌段共聚物(P(n-BMAb-NIPAM))。考察了引发剂、催化剂、反应温度等对聚合反应结果的影响,最终确定较为合适的反应条件,制备出分子量确定、分子量分布较窄的大分子引发剂,并成功引发第二单体继续通过ATRP反应,获得P(nBMA-b-NIPAM)。研究结果表明:所确定的ATRP反应体系能实现n-BMA的可控聚合,获得末端带溴原子的聚甲基丙烯酸正丁酯(P(n-BMA-Br))作为大分子引发剂继续通过ATRP反应引发N-异丙基丙烯酰胺(NIPAM),最后获得分子量确定、分子量分布较窄的嵌段共聚物P(n-BMA-b-NIPAM)。实验证明,利用高价态铜络合体系可以实现单体的可控聚合,而且可以保持聚合物末端较高的卤官能度。     

温度感应复合型控制释放膜系统的性能研究

采用等离子诱导填孔接枝聚合法将聚N-异丙基丙烯酰胺(PNIPAM)开关接枝到聚偏氟乙烯膜(PVDF)膜孔上,同自由基聚合法制备的PNIPAM交联水凝胶结合,成功地组成了一种温度感应复合型控制释放膜系统。在该膜系统中,PNIPAM接枝PVDF膜作为控制释放开关,PNIPAM交联水凝胶作为药物载体。通过改变交联水凝胶和开关膜的微观结构,研究了该复合膜系统的温度感应控制释放特性。结果表明,该复合膜系统具有良好的温度感应特性,优于单独的开关膜控制释放系统或是单独的交联水凝胶控制释放系统。研究结果将为温度感应型控制释放系统或给药系统的设计与开发提供理论基础。     

双响应性嵌段聚合物的纳米孔开关效应的计算机模拟

利用计算机模拟方法(耗散粒子动力学)研究了双响应性嵌段聚合物修饰的纳米孔的开关效应。通过在纳米孔内接枝具有温度和pH响应的嵌段聚合物(N-异丙基丙烯酰胺和丙烯酸),研究不同嵌段序列(即wall-PNIPAM-PAA或wall-PAA-PNIPAM)对纳米孔开关效应的影响,结果表明,只有wall-PNIPAM-PAA嵌段序列可以实现纳米孔在不同条件下的开关效应。同时还探究了接枝密度、链长和嵌段比例对纳米孔开关效应的影响,结果表明,中高等接枝密度、适合的链长和中等比例的嵌段比可以实现不同特征的纳米孔,用于控制纳米孔的开关效应。     

聚偏氟乙烯膜材料的表面改性及其膜的制备

在高温条件下,将丙烯酸接枝到聚偏氟乙烯上,制备出了有pH响应的开关膜,考察了不同温度、不同时间及不同单体量对接枝率的影响,并且对膜的pH敏感性能及亲水性进行了研究。结果表明用热接枝聚合能合成pH敏感膜,但接枝率普遍不高。     

卟啉端基化聚(N-异丙基丙烯酰胺)-b-聚(寡聚乙二醇甲醚甲基丙烯酸酯)共聚物的温敏性

以N-异丙基丙烯酰胺(NIPAM)和寡聚乙二醇甲醚甲基丙烯酸酯(OEGMA)为原料,通过可逆加成裂解链转移自由基聚合制备了一系列卟啉端基化嵌段共聚物,通过傅里叶变换红外光谱和核磁共振氢谱对其结构进行了表征,并对其温敏性和pH值响应性进行了研究.结果表明,所得卟啉端基化共聚物为聚(N-异丙基丙烯酰胺)-b-聚(寡聚乙二醇...     

温敏性PVDF/PGS-g-PNIPAM纳米复合超滤膜的制备和性能

通过化学接枝法将聚(N-异丙基丙烯酰胺)(PNIPAM)接枝聚合在凹凸棒石(PGS)纳米纤维表面,制备了系列接枝率的温敏性PGS-g-PNIPAM纳米颗粒,将其与聚偏氟乙烯(PVDF)共混制备温敏性纳米复合超滤膜,深入研究PNIPAM接枝率对膜结构和性能的影响。结果表明,凹凸棒石表面PNIPAM接枝率随溶液中NIPAM单体浓度增大而增加;PGS-g-PNIPAM使复合膜中PVDF晶核变小,数目增多,膜更为疏松多孔,PVDF/PGS-g-PNIPAM膜的平均孔径在20 nm左右,膜的平均孔径和最大孔径均随凹凸棒石表面PNIPAM 接枝率的增加而增大;PVDF/PGS-g-PNIPAM膜具有温敏性,温敏开关系数随PNIPAM接枝率的增加先增强后减弱,当接枝率为21.33%时膜温敏开关系数最大,达到1.51,膜渗透通量也最大,对牛血清白蛋白具有良好的截留和抗污染性能。     

N-异丙基丙烯酰胺共聚物的温度敏感性研究

通过自由基聚合合成了 N-异丙基丙烯酰胺和甲基丙烯酸甲酯及甲基丙烯酸的共聚物。研究了甲基丙烯酸甲酯和甲基丙烯酸的加入对聚 N-异丙烯酰胺温度敏感性的影响 ,并考察了溶液中盐浓度和 p H对共聚物温度敏感性的影响     

聚N-异丙基丙烯酰胺接枝核孔膜微观结构及温敏响应特性

采用等离子体诱导填孔接枝聚合法在聚碳酸酯核孔（PCTE）膜上成功地接枝了聚N-异丙基丙烯酰胺（PNIPAM）,采用X射线光电子能谱（XPS）、傅里叶变换红外光谱仪（FT-IR）、扫描电镜（SEM）、原子力显微镜（AFM）、接触角测量仪和水通量实验,系统地研究了PNIPAM-g-PCTE膜的化学成分、微观结构和温敏特性,以期为环境感应型开关膜的设计和制备提供指导.结果表明,PNIPAM被均匀地接枝在PCTE膜表面和膜孔中;当填孔率F<44.2%时,PNIPAM-g-PCTE膜的膜孔由于孔内接枝物的体积变化而表现出温敏开关特性,并且膜孔径随着F的增大而减小;当F>44.2%以后,水溶液中膜的膜孔被溶胀的PNIPAM接枝链堵塞,此时PNIPAM-g-PCTE膜不再具有温度开关特性;40 ℃时膜孔被完全堵塞的临界填孔率范围在30%～40%之间;随着温度从25 ℃增加到40 ℃,PNIPAM-g-PCTE膜表面的接触角也从58.5°增加到87.9°;PNIPAM-g-PCTE膜水通量的温敏开关特性主要取决于膜孔径的变化,而不是膜表面亲水性的改变.     

Aggregation behaviour of well defined amphiphilic diblock copolymers with poly(N-isopropylacrylamide) and hydrophobic blocks

Series of amphiphilic diblock copolymers with poly(N-isopropylacrylamide) as a hydrophilic block and a hydrophobic block consisting of either polystyrene or poly(tert-butyl methacrylate) were synthesised using RAFT polymerisations. Differential scanning calorimetry showed the chemically different blocks being phase separated in dry polymers. Light scattering and microcalorimetry studies were performed on aqueous solutions to investigate the phase behavior of the diblock copolymers. By carefully transferring the polymers from an organic solvent to water, either micellar particles or large aggregates were obtained depending on the relative lengths of the blocks. Large aggregates collapsed upon heating, whereas collapse occurred slowly within a broad temperature range in the case of micelle like structures. However, microcalorimetrically the collapse of the PNIPAM chains was observed to take place in all samples, suggesting that the shells of the micellar particles are crowded in a way which hinders the compression of the poly(N-isopropylacrylamide) chains.     

Structural Organization of Interpolymer Complexes Formed by Poly(<Emphasis Type="Italic">N</Emphasis>-vinylamides) and Poly(methacrylic acid) Chains Regularly Grafted to Polyimide in Aqueous Solutions

The formation and structural organization of interpolymer complexes formed by poly(methacrylic acid) chains regularly grafted to polyimide (molecular brushes) and macromolecules of poly(N-vinylamides) with different molecular masses are studied by polarized luminescence. The luminescent label of the anthracene structure is covalently bound to poly(methacrylic acid) chains in a brush. It is shown that in aqueous solutions the complexes under study are stabilized by hydrogen bonds formed between proton donor and proton acceptor groups of interacting chains. The formation of these complexes depends not only on the nature of poly(N-vinylamide) but also especially on its molecular mass. An increase in the molecular mass of polyamide is followed by the formation of a more compact less hydrated structure, as proved by an increase in the time of nanosecond relaxation and enhanced binding of the diphilic organic ion. The hindrance of poly(methacrylic acid) grafted chains complexed with polyvinylamide is lower than that of corresponding linear chains. This can be explained by a higher imperfection of the formed double-stranded structures. The ionization of carboxyl groups leads to the dissociation of complexes. The pH range corresponding to the highest degree of binding of acridine orange by poly(methacrylic acid) grafted chains is broader than that corresponding to the highest degree of dye binding by the linear polyacid.     

智能膜开关尺寸与孔径的匹配性对膜响应性能的影响规律

智能膜的响应性能是其主要性能之一。本文借助计算流体力学（CFD）模拟,以孔壁排布有聚N-异丙基丙烯酰胺（PNIPAM）智能微球的单直膜孔为模型,定量系统地考察了智能微球的响应倍数以及微球尺寸与膜孔径的匹配性对膜温度响应性能的影响规律,并通过实验验证了模拟结果的可靠性。CFD模拟结果表明,当智能开关与膜孔径的相对比值一定时,温度响应开关系数随着微球响应倍数的减小而逐渐增大。当相对比值小于0.4时,实测的温度响应开关系数与固载量100%的模拟结果相吻合;而当相对比值大于0.4时,其与固载量为67%的模拟结果相吻合。通常当相对比值在0.4～0.65之间时,智能膜可以同时获得良好的温度响应性能和稳定的渗透性能。该研究结果可望为设计和制备高性能智能膜提供理论指导和实验基础。     

PH值与温度感应型智能开关膜的研究

利用等离子体诱导填孔接技聚合法将聚异而基丙烯酰胺(PNIPAM)或聚丙烯酸(PAAC)接枝聚合在聚偏氟乙烯(PVDF)微孔膜上,制备了一系列具有较宽接枝率范围的温度感应型开关膜(接枝PNIPAM)和pH值感应型开关膜(接技PAAC),研究了接枝率对膜的温度感应以及pH值感应开关特性的影响。研究结果表明,开关膜的接枝率对膜的开关特性有十分重要的影响。对于温度感应型开关膜,当接枝率等于2.81％时,可以获得最好的膜孔开关特性;而且发现在溶质扩散时,低接枝率膜与高接技率膜呈现两种完全相反的开关特性。对于pH值感应型开关膜,当接枝率为1.01％时膜孔开关特性最好。因此,为了获得预期的开关特性,必须将接枝率控制在合适的范围内。     

Doubly thermo-responsive brush-linear diblock copolymers and formation of core-shell-corona micelles

Doubly thermo-responsive brush-linear diblock copolymer of poly[poly(ethylene glycol) methyl ether vinylphenyl]-block-poly(N-isopropylacrylamide) (PmPEGV-b-PNIPAM) is prepared by RAFT polymerization. The obtained brush-linear diblock copolymer exhibits two lower critical solution temperatures (LCSTs) corresponding to the linear poly(N-isopropylacrylamide) (PNIPAM) block and the brush poly[poly(ethylene glycol) methyl ether vinylphenyl] (PmPEGV) block in water. This brush-linear diblock copolymer undergoes a two-step temperature sensitive micellization. At temperature above the first LCST, the brush-linear diblock copolymer self-assembles into core-corona micelles with the dehydrated PNIPAM block forming the core and the solvated brush PmPEGV block forming the corona. When temperature increases above the second LCST, the polystyrene backbone in the brush PmPEGV block collapses onto the dehydrated PNIPAM core to form core-shell-corona micelles, in which the dehydrated PNIPAM block forms the core, the collapsed polystyrene backbone in the brush PmPEGV block forms the shell and the solvated poly(ethylene glycol) side-chains forms the corona. The effect of the length of the PNIPAM block and the length of the poly(ethylene glycol) side-chains on the thermo-responsive micellization and the size of core-shell-corona micelles is investigated.     

Thermo‐Responsive Gating Characteristics of Poly(N‐isopropylacrylamide)‐Grafted Membranes

Both hydrophilic Nylon‐6 membranes and hydrophobic poly(vinylidene fluoride) (PVDF) membranes, with a wide range of grafting yields of poly(N‐isopropylacrylamide) (PNIPAM), were prepared using the plasma‐graft pore‐filling polymerization method. The effect of the physical and chemical properties of the substrates on the thermo‐responsive gating characteristics of the PNIPAM‐grafted membranes was investigated experimentally. For both the PVDF and Nylon‐6 membranes, the grafted PNIPAM polymers were found not only on the membranes outer surface, but also on the inner surfaces of the pores throughout the entire thickness of the membrane. The thermo‐responsive gating characteristics of the PNIPAM‐grafted membranes were heavily affected by the physical and chemical properties of the porous membrane substrates. The PNIPAM‐g‐Nylon‐6 membranes exhibited a much larger thermo‐responsive gating coefficient than the PNIPAM‐g‐PVDF membranes. Furthermore, to achieve the largest thermo‐responsive gating coefficient, the corresponding optimum grafting yield of PNIPAM for the PNIPAM‐g‐Nylon‐6 membranes was also larger than that for the PNIPAM‐g‐PVDF membranes.     

Improving the antifouling property of poly(vinyl chloride) membranes by poly(vinyl chloride)‐g‐poly(methacrylic acid) as the additive

To improve the antifouling property of poly(vinyl chloride) (PVC) membranes, a series of poly(methacrylic acid) grafted PVC copolymers (PVC‐g‐PMAA) with different grafting degree were synthesized via one‐step atom transfer radical polymerization process utilizing the labile chlorines on PVC backbones followed by one‐step hydrolysis reaction. PVC/PVC‐g‐PMAA blend membranes with different grafting degree and copolymer content were prepared by nonsolvent induced phase separation method. The surface chemical composition, surface charge, membrane structures, wettability, permeability, separation performances and the fouling resistance of blend membranes were carefully investigated. The results indicated that the PMAA chains were segregated towards the surface and the membranes were endowed with negative charge. The hydrophilicity and permeability of the blend membranes were obviously improved. Furthermore, the antifouling ability especially at neutral or alkaline environments was also significantly increased. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42745.     

pH and thermo‐responsive poly(N‐isopropylacrylamide) copolymer grafted to poly(ethylene glycol)

pH and thermo‐responsive graft copolymers are reported where thermo‐responsive poly(N‐isopropylacrylamide) [poly(NIPAAm), poly A ], poly(N‐isopropylacrylamide‐co‐2‐(diethylamino) ethyl methacrylate) [poly(NIPAAm‐co‐DEA), poly B ], and poly(N‐isopropylacrylamide‐co‐methacrylic acid) [poly(NIPAAm‐co‐MAA), poly C ] have been installed to benzaldehyde grafted polyethylene glycol (PEG) back bone following introducing a pH responsive benzoic‐imine bond. All the prepared graft copolymers for PEG‐g‐poly(NIPAAm) [ P‐N1 ], PEG‐g‐poly(NIPAAm‐co‐DEA) [ P‐N2 ], and PEG‐g‐poly(NIPAAm‐co‐MAA) [ P‐N3 ] were characterized by ¹H‐NMR to assure the successful synthesis of the expected polymers. Molecular weight of all synthesized polymers was evaluated following gel permeation chromatography. The lower critical solution temperature of graft copolymers varied significantly when grafted to benzaldehyde containing PEG and after further functionalization of copolymer based poly(NIPAAm). The contact angle experiment showed the changes in hydrophilic/hydrophobic behavior when the polymers were exposed to different pH and temperature. Particle size measurement investigation by dynamic light scattering was performed to rectify thermo and pH responsiveness of all prepared polymers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013