环糊精星形聚合物稳定的纳米金银溶胶的合成研究

【作者】 孙华明；

【导师】 高子伟；

【作者基本信息】 陕西师范大学 ， 材料学， 2008， 硕士

【摘要】 纳米金属胶体由于具有许多本体所不具备的独特物理和化学性能,在光学、电学、磁学、催化剂、传感、生物医学等领域显示出了巨大的应用潜力。因此合成方法简便,粒径和形状可控的金属胶体粒子的制备一直是纳米材料科学中富有挑战性的课题。星形聚合物是由化学组成相同的多个线形支链通过化学键连接到同一个中心核上而形成的一类聚合物。近年来,星形聚合物引起了人们的广泛关注。因此,设计新的多臂星形聚合物,开发星形聚合物在材料科学上的应用仍是当前研究的热点问题。环糊精(β-Cyclodextrin,简称β-CD)是一个中空环状低聚糖化合物,具有腔内疏水、腔外亲水的两亲性特点。此外,β-环糊精有许多可以功能化的羟基基团,可以用来制备多臂星形聚合物。聚甲基丙烯酸二甲氨基乙酯(PDMAEMA)是一类具有温度敏感和pH敏感的聚合物,广泛用于环境保护、药物缓释和基因治疗等领域。设计以环糊精为核的甲基丙烯酸二甲氨基乙酯多臂星形聚合物(CD-PDMAEMA),则可以保留甲基丙烯酸二甲氨基乙酯和环糊精两种基本结构单元。这种多臂星形聚合物有望在功能方面尤其在纳米胶体的制备上获得更加有意义的结果。基于以上述考虑,本论文在简述纳米金属胶体和有关星形聚合物研究进展基础上,采用原子转移自由基聚合(ATRP)技术,制备了以环糊精为核的甲基丙烯酸二甲氨基乙酯星形聚合物。然后在CD-PDMAEMA存在下,室温下成功合成了纳米金银胶体,并对其形成机理进行了初步探讨。取得的主要研究结果如下:1、以环糊精溴化物(β-CD-Br)为引发剂、氯化亚铜(CuCl)为催化剂、邻菲罗啉(o-phcn)为配位剂、丙酮和水为溶剂,在25℃下用ATRP合成了以环糊精为核的甲基丙烯酸二甲氨基乙酯星形聚合物。并经FF-IR、~1H-NMR等手段对星形聚合物进行了结构表征。考察了不同反应时间对聚合反应的影响,GPC结果表明所得的CD-PDMAEMA的分子量随时间的增长而增大,所得聚合物的分子量分布都很窄(Mw/Mn＜1.10)。2、以CD-PDMAEMA同时作为稳定剂和还原剂,水为溶剂,在室温下一步法合成了分散性很好、尺寸均匀、粒径大约为10 nm左右的纳米金胶体粒子,并通过UV-Vis、FT-IR、XRD、SAED、TEM和DLS等手段对其进行了分析表征。结果表明,初始溶液中N/Au原子摩尔比率和星形聚合物的初始pH值是影响纳米金胶体制备的重要因素。通过改变N/Au摩尔比率和溶液的初始pH值,可以对纳米金胶体粒子的粒径进行调控,其中初始溶液中N/Au原子摩尔比率为6:1,初始CD-PDMAEMA溶液在中性偏碱性(pH=7～11)条件下制备的纳米金溶胶较佳。3、以CD-PDMAEMA同时作为稳定剂和还原剂,水为溶剂,在室温下一步法合成了分散性较好、尺寸较均匀的纳米银胶体粒子,并用FT-IR,UV-Vis和TEM对其进行了表征。结果表明,初始溶液中N/Ag原子摩尔比率和星形聚合物的初始pH值是影响纳米银胶体制备的重要因素。通过改变N/Ag摩尔比率和溶液的初始pH值,可以对纳米银胶体粒子的粒径进行调控。初始溶液中N/Ag原子摩尔比率为6:1,初始星形聚合物溶液在中性偏碱性(pH=7～10)条件下制备的纳米银溶胶较佳。更多还原

【Abstract】 The metal colloids have the unique physical and chemical properties that are neither those of bulk materials nor those of molecular compounds.They have been exploited for the extensive potential applicationsinoptics,electronics,magnetic,catalyst,sensing,biomedicine,etc.The development of simple and versatile methods for the preparation of nanoparticles in a size-or shape-selected and-controlled manner is an important and challenging task.Star polymers are characterized as structures in which all the chains of a molecule are linked together to a small-molar-mass core.More recently,star polymers see increasingly widespread application in nanotechnology.As a consequence,the design and synthesis of the multi-armed star polymers as well as their functionalities in materials are highly sought after.β-Cyclodextrins（β-CDs） are a series of cyclic oligosaccharides composed of glucose units linked byα-1,4 linkage.They have polar hydrophilic outer shells and hydrophobic cavities. Furthermore,becauseβ-CDs possesses many hydroxyl groups,it should be used for conforming star polymers as well.It is well known that poly（dimethylaminoethyl methacrylate）（PDMAEMA） can undergo a conformational transition due to hydrophobic or hydrophilic molecular chain interactions by varying pH value and temperature.So dimethylaminoethyl methacrylate star polymers with cyclodextrin core（CD-PDMAEMA） were synthesized and it can be expected to obtain better results in the synthesis of metal colloids materials with the multi-armed star polymers.Based on the above,the recent development of metal colloids and synthesis of star polymers were simplely introduced,and the synthesis of CD-PDMAEMA were achieved by atom transfer radical polymerization.Gold and silver colloids were also prepared successfully at ambient temperature with CD-PDMAEMA.The main results obtained in this thesis are as follows.1.The synthesis of CD-PDMAEMA has been achieved successfully by atom transfer radical polymerization in aqueous acetone at ambient temperature using CuCl as catalyst,o-phen as a ligand reagent andβ-CD-Br as the initiator,respectively.The influence of different reaction time on the polymerization were studied.GPC results confirmed CD-PDMAEMA have low polydispersity （Mw/Mn＜1.10）.The star polymer was characterized by FT-IR and ¹H-NMR.2.Gold colloids were prepared by reducing aqueous solutions of HAuCl₄ at ambient temperature with CD-PDMAEMA,which acted as both reducing and stabilizing agents for the formation of gold nanoparticles.The product was characterized by UV-Vis spectrum,FT-IR,XRD, SAED,TEM and DLS.It was also found that N/Au mole ratio and pH was the very important factor in preparating gold colloids.The size of gold nanoparticles could be controllable by the change of N/Au mole ratio and pH in aqueous solution.N/Au=6:1 and pH=7～11 is the best experiment condition.3.Silver colloids were prepared by reducing aqueous solutions of AgNO₃ at ambient temperature with CD-PDMAEMA,which acted as both reducing and stabilizing agents for the formation of silver nanoparticles.The product was characterized by UV-Vis spectrum,FT-IR and TEM.It was also found that N/Ag mole ratio and pH was the very important factor in preparating silver colloids.The size of silver nanoparticles could be controllable by the change of N/Ag mole ratio and pH in aqueous solution.N/Ag=6:1 and pH=7～10 is the best experiment condition.更多还原