【作者】 孙家英；

【导师】 张立武；

【作者基本信息】 重庆大学 ， 分析化学， 2007， 硕士

【摘要】 星形聚合物是一类最简单的、特殊的支化聚合物,具有独特的三维雪花状结构,是各种功能和性能的新材料。其新奇的结构,独特的性能及其潜在的应用前景,成为最近研究的热点。原子转移自由基聚合(ATRP)是高分子化学的重要技术,是实现高分子设计,合成具有特定结构和性能的高分子的重要手段。其适用的单体范围较广,聚合条件温和、没有聚合方法的限制,适宜于本体聚合、溶液聚合、乳液聚合、悬浮聚合等。通常合成星形聚合物的路线有两条:先臂法和先核法。本文通过ATRP,采用先核法,分别利用本体聚合、溶液聚合制备四臂星形聚苯乙烯。其开展的工作主要如下:(1)四臂星形聚苯乙烯的制备。利用多官能团引发剂1,2,4,5-四溴甲基苯(TBMB),在催化体系溴化亚铜(CuBr)/2,2′-联吡啶(2,2′-bpy)存在下,引发单体苯乙烯(St)的溶液及本体聚合,制备四臂星形聚苯乙烯(PSt)。通过改变单一聚合条件,在不同反应时间,利用注射器进行取样,称重法测定聚合物转化率,考察聚合条件的影响,说明此合成体系受单体/引发剂、催化体系、聚合温度、反应时间等因素的影响(如聚合温度90℃,反应时间12h时,产率可达90%以上)。(2)聚合条件的优化。由于聚合过程受上述多种因素影响,分别利用正交、均匀、中心试验设计方法,综合考察聚合条件诸如单体/引发剂、催化体系、聚合温度、反应时间等因素对聚合体系的影响;并运用直观分析、方差分析、多元线形回归、逐步回归等数据处理方法对实验数据进行处理、分析和优化,获得聚合的最佳实验条件(如正交试验中最佳实验条件:[M]/[I]为14.4800g/0.0500g、CuBr/Bpy为0.06g/0.1960g(1:3)、温度为100℃、时间为10小时)。而且通过以上正交、均匀、中心试验设计方法所得到数据进行分析并建模,其模型的稳定性、相关性及预测能力都较好(如正交试验中:本体聚合法中R=0.999、溶液聚合法R=0.987;均匀试验中:本体聚合法中R=0.996、溶液聚合法R=0.990;中心试验中:本体聚合法中R=0.978,溶液聚合法R=0.982)。通过上述多种试验设计方法,分别利用溶液和本体聚合法考察对聚合过程的影响,表明两种聚合方法在合成时各有其优缺点。(3)星形聚苯乙烯粘度的测定。利用乌氏粘度计(Ubbelohde Vislometer),在23℃四氢呋喃溶液中,测定四臂星形聚苯乙烯的特性粘度,用公式[η]=KMα计算其粘均分子量(Mη)。并在相同的粘均分子量下,计算线性聚苯乙烯粘度η线,其值比星形聚苯乙烯粘度的大得多。(4)综合结构分析表征。采用紫外(UV)、核磁共振(1H-NMR、13C-NMR、1H -1HCOSY)、红外光谱(IR)对聚合物结构进行综合分析。利用凝胶渗透色谱(Gel Permeation Chromatography,GPC)测定星形聚合物的数均分子量及其分子量分布(DP),且Mn,GPC比Mn,th小。基于端基分析通过NMR测定,计算聚合物的数均分子量(Mn,NMR),Mn,NMR与Mn,th基本相符,其结果表明定量引发效率。并且通过NMR图谱计算聚合物的立构规整性,其聚合产物中间同结构相对含量超过百分之八十。(5)利用综合热分析仪(STA449C)对星形聚合物进行综合热分析。差示扫描量热法(DSC)分析聚合物的玻璃化转变等,利用多元线形回归对多元线性回归建立模型预测玻璃化转变温度(Tg),其模型的R=0.973,交互检验得Rcv=0.923,说明所建的模型具有很好的相关性、稳定性、预测能力。热重法(TG)对星形聚合物进行热稳定性及分解过程分析,发现星形聚合物的行为与该聚合物的臂长度有关。通过以上正交、均匀、中心试验设计方法对聚合条件的优化以及对所合成的聚合物进行综合分析表征,表明原子转移自由基聚合过程可控,而且所合成的聚合物为结构明确的四臂星形聚聚苯乙烯,分子量可控、分子量分布都小于1.5,符合原子转移自由基聚合特征。更多还原

【Abstract】 Star-shaped polymers are new important materials with unique three dimensional snowflake structures, unfamiliar configurations, various functions, special performances, particular capabilities and potential applications. As the simplest and specially branched polymers, they become one of the recent research hotspots with useful prospects.Atom transfer radical polymerization (ATRP) is an important technique in macromolecule chemistry and a useful pathway to realize molecular design and chemical synthesis of polymers with different structures and special performances. ATRP is applicable to various polymerizations in bulk, solution, emulsion, suspension and some others due to its many strong-points, for example, more monomers, milder conditions, unlimited methods and so forth. As a rule, there are two ways, namely, both“arm-first”and“core-first”methods in order to synthesize star-shaped polymers.In this thesis, four-arm polystyrene has been synthesized as one of star-shaped polymers via atom transfer radical polymerization by using“core-first”method through both solution and bulk polymerizations, respectively. The main contents and some conclusions are shown and made as follows:1. Four-arm star-shaped polystyrenes with an 1,2,4,5-tertra(bromomethyl benzene, TBMB) core were prepared by atom transfer radical polymerization (ATRP). Both bulk and solution polymerizations of styrene were performed by using 1,2,4,5-tertra(bromomethyl benzene) as the multifunctional initiator and CuBr/2,2′-bipyridine (2,2′-bpy) as the catalyst system. Through changing various conditions, the conversion of polymerization was determined gravimetrically by sampling with an injector at different time in the course of polymerization system and it was found that conversion was increased linearly firstly and non-linearly finally along with reaction time. Results indicated effect factors of polymerization system, which were monomer/initiator, catalysis system, temperature and time, Changed single polymeric condition and researched infection of polymeric conditions.2. For the complicated polymerization system, orthogonal, uniform and central experimental designs were employed to examine various influence factors such as monomer/initiator ratio, catalysis system, reaction temperature and polymerization time. Intuitive analysis, variance analysis, multiple linear and/or stepwise regressions were used to process experimental data to find the optimum experimental conditions(for example: the optimum experimental conditions of orthogonal experimental designs: [M]/[I]: 14.4800g/0.0500g, CuBr/Bpy: 0.06g/0.1960g(1:3), temperature:100℃, time:10 hours). And that stabilities, relativities and forecasting abilities of models were preferable (for instance: R=0.999, 0.996, 0.978 for the bulk polymerization; R=0.987, R=0.990, R=0.982 for the solution polymerization) by orthogonal, uniform and central experimental designs, respective. Both solution and bulk polymerizations were examined for optimum conditions; and it found that each had merits and faults, respectively.3. Viscidity of four arms star-shaped polystyrene was determined with Ubbelohde vislometer at 23°C, by using tetrahydrofuran as solvent. Viscidity average molecular weight (Mη) was calculated by formula [η]=KMα(K=3.5×10-3ml/g;α=0.74). While, viscidity of linear polystyrene was also determined simultaneously as the same viscidity average molecular weight and it was found the viscidity was much larger than that of star polystyrene.4. Various structures of polymers were analyzed with different spectroscopies, such as UV, IR, 1H-NMR, 13C-NMR and 1H-1H COSY. Number-average molecular weight and distribution of star-shaped polymers were determined with GPC characterization. Moreover, Mn,GPC was much smaller than Mn,th. Based on terminal functional groups analysis, Mn,NMR was calculated by NMR spectra and basically accorded with both Mn,NMR and Mn,th each other, which reveals the quantitative initiation efficiency. And steric tactility was then determined by NMR spectra. Syndiotactic rate of polymers was more than 80% for their relative contents.5. Thermal analysis was performed on thermometry model STA449C for star-shaped polymers. Glass transition was analyzed by differential scanning calorimetry (DSC), and glass transition temperature (Tg) was then obtained by multiple linear ingression (MLR) with correlation coefficients being R=0.973, and Rcv=0.923 from model estimation and cross verification, respectively. Decomposition course and thermal stability were evaluated with theremogravimetry (TG). It was found that four-arm star polymer behaviors were correlated with arm length of the four-arm star polymer.In summary, four-arm star-shaped polystyrene cored with an 1,2,4,5-tertra(bromomethyl benzene) as the multifunctional initiator has been synthesized via atom transfer radical polymerization by using CuBr/2,2′-bpy as the catalyst system under optimal experimental conditions. And that various characterization results indicated that the prepared star-shaped polymers had well-defined four-arm structures and relatively-narrow molecular weight distribution.更多还原