温敏性PNIPAM-AuNPs和PNIPAM-DNA的制备及性能研究

发布时间：2018-12-30 10:54

【摘要】：聚(N-异丙基丙烯酰胺)又称PNIPAM是一种温敏性的高分子聚合物,对温度具有很好的刺激响应性。在最低临界溶解温度(LCST)处会发生构象转变,若温度在LCST以下,PNIPAM通过酰胺基与水形成氢键,使其可以在水中稳定存在,水分子包围在疏水基团周围,此时PNIPAM具有亲水性,其在水溶液中为自由伸展态;若温度在LCST以上,氢键断裂,PNIPAM自身的酰胺基之间形成氢键,使其内部坍塌,由伸展态转为球形结构。若加以改性,可拓宽温敏性聚合物材料的研究领域,使其在药物负载运输,基因传递,化学分析等领域里发挥更大的应用价值。论文基于可逆加成断裂链转移聚合(RAFT)聚合原理及乙醇胺氨解作用制备PNIPAM-Au NPs复合物,研究各种盐离子对PNIPAM-Au NPs复合物的盐效应,基于电子转移活化催化剂的原子自由基聚合(AGET ATRP)聚合原理及点击化学(Click)反应原理,制备PNIPAM-DNA嵌段共聚物,研究DNA构象变化引起的PNIPAM-DNA共聚物LCST变化情况。主要的研究内容如下:1.采用氰基戊酸二硫代苯甲酸(CPADB)作链转移剂、偶氮二异丁氰(AIBN)作引发剂,在N,N-二甲基甲酰胺(DMF)溶剂中通过RAFT聚合制备PNIPAM-COOH,合成的PNIPAM-COOH具有可控分子量且分子量多分散性较低;同时采用溴异丁酸乙酯(EBIB)/五甲基二乙烯三胺(PMDETA)/溴化铜作引发催化剂、抗坏血酸作还原剂,通过AGET ATRP聚合合成了PNIPAM-Br,表征结果表明合成的PNIPAM-COOH及PNIPAM-Br均具有明确结构。2.利用乙醇胺的氨解作用,将PNIPAM-COOH聚合物一端的二硫酯键还原为巯基,然后将其嫁接到纳米金表面,制备PNIPAM-AuNPs复合物。水溶液中聚合物稳定存在,而不同盐离子对其有不同的盐效应,实验发现,低温时受离子所带电荷及复合物与盐离子的络合作用的综合影响,影响效果为Hg2+Cu2+Zn2+Ni2+Pb2+Na+;高温时,热效应和盐效应的共同作用使得复合物在很低的盐离子浓度时即可聚集,影响效果为Cu2+Pb2+Zn2+Ni2+Hg2+Na+,同时离子的络合作用很微弱,但离子所带电荷影响效果却依然很强,从而使得Cu2+与Pb2+作用效果相近,Zn2+稍次,Hg2+和Ni2+相近,Na+盐溶液对其的影响依然最低。3.通过叠氮化钠将PNIPAM-Br末端溴基置换为叠氮基,利用click反应嫁接末端为炔基的DNA,制备PNIPAM-DNAC和PNIPAM-DNAT嵌段共聚物,分别检测不同温度下,PNIPAM-DNAC在酸碱性溶液中及PNIPAM-DNAT在汞离子加入前后的溶液透过率,研究DNA构象变化引发的共聚物LCST变化情况。结果发现,DNAC在酸性溶液中(pH6.0)由单链结构转为四面体结构,DNAT在汞离子存在下通过T-Hg2+-T结构杂交为双链,这些构象变化可使得DNA上带有的负电荷增多、链间斥力加强,使PNIPAM-DNA嵌段共聚物相转变温度范围变宽、变化平缓、动力学半径降低、溶液透过率提高。
[Abstract]:Poly (N-isopropyl acrylamide), also known as PNIPAM, is a kind of high molecular polymer with temperature sensitivity, which has a good stimulus response to temperature. At the lowest critical solution temperature (LCST), conformational transition occurs. If the temperature is below LCST, PNIPAM forms a hydrogen bond with water through the amide group, so that it can exist stably in water, and the water molecules are surrounded by hydrophobic groups, so that PNIPAM is hydrophilic. It is a free extensional state in aqueous solution. If the temperature is above LCST, the hydrogen bond breaks, and the hydrogen bond between the amide groups of PNIPAM itself is formed, which causes the internal collapse of the bond and changes from the extensional state to the spherical structure. If modified, it can broaden the research field of thermo-sensitive polymer materials and make it play a more important role in drug loading, gene transmission, chemical analysis and other fields. Based on the principle of reversible addition chain transfer polymerization (RAFT) polymerization and ethanolamine ammonolysis, PNIPAM-Au NPs complexes were prepared. The salt effects of various salt ions on PNIPAM-Au NPs complexes were studied. PNIPAM-DNA block copolymers were prepared by atom radical polymerization of (AGET ATRP) and click-chemical (Click) reaction on the basis of electron transfer activation catalyst. The LCST changes of PNIPAM-DNA copolymers induced by conformation change of DNA were studied. The main research contents are as follows: 1. Using dithiobenzoic acid (CPADB) as chain transfer agent and (AIBN) as initiator, PNIPAM-COOH, was prepared by RAFT polymerization in the solvent of N- dimethylformamide (DMF). The synthesized PNIPAM-COOH has controllable molecular weight and low molecular weight polydispersity. At the same time, PNIPAM-Br, was synthesized by AGET ATRP polymerization with ethyl bromide (EBIB) / (PMDETA) / copper bromide as initiator and ascorbic acid as reducing agent. The characterization results show that the synthesized PNIPAM-COOH and PNIPAM-Br have clear structures. 2. Based on the ammonolysis of ethanolamine, the dithioester bond at one end of PNIPAM-COOH polymer was reduced to mercapto group, and then it was grafted onto the surface of nanometer gold to prepare PNIPAM-AuNPs complex. The polymer exists stably in aqueous solution, but different salt ions have different salt effect on it. It is found that at low temperature, the polymer is affected by the charge of ions and the complex complexation with salt ions, and the effect is Hg2 Cu2 Zn2 Ni2 Pb2 Na. At high temperature, the interaction of thermal effect and salt effect makes the complex gather at very low salt ion concentration, the effect is Cu2 Pb2 Zn2 Ni2 Hg2 Na, and the complexation effect of ion is very weak. However, the effect of ion charge is still very strong, so that the effect of Cu2 and Pb2 is similar, Zn2 is less, Hg2 and Ni2 are close, and the effect of Na salt solution is still the lowest. The PNIPAM-Br terminal bromine group was replaced with azide group by sodium azide. The block copolymers of PNIPAM-DNAC and PNIPAM-DNAT were prepared by click reaction grafting DNA, with acetylene group. The results showed that the PNIPAM-DNAC and PNIPAM-DNAT block copolymers were tested at different temperatures. The transmittance of PNIPAM-DNAC in acid-base solution and PNIPAM-DNAT in the solution before and after the addition of mercuric ion was studied to study the change of LCST induced by the conformation change of DNA. The results showed that DNAC changed from single strand structure to tetrahedron structure in acid solution (pH6.0), and DNAT was hybridized into double strand by T-Hg2 T structure in the presence of mercury ion. These conformational changes resulted in the increase of negative charge on DNA. The repulsive force between chains increases the temperature range of phase transition of PNIPAM-DNA block copolymers, the change is gentle, the kinetic radius is decreased, and the transmittance of the solution is increased.
【学位授予单位】：鲁东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O633.22

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