【作者】 陈莉；

【导师】 郭丽萍；

【作者基本信息】 武汉理工大学 ， 应用化学， 2010， 硕士

【摘要】 凝胶渗透色谱(GPC)在测定聚电解质分子量及其分布的过程中由于缺乏合适的标样,以及非体积效应,使其结果存在较大误差。本文的研究工作包括以下几个方面：(1)采用水溶液自由基聚合,合成出不同分子量范围的聚丙烯酸(PAA)标样粗品。以二氧六环为良溶剂,石油醚为沉淀剂,通过二次等温沉淀分级,制得8个不同分子量的PAA标样,并用渐进校正法建立了GPC校正曲线。由该曲线得到的粘均分子量与粘度法测得的分子量相比其平均相对误差为7%,得到的数均分子量与端基滴定法测得分子量相比平均相对误差为9%。(2)以上述PAA标样的峰值分子量和峰值淋洗体积建立GPC工作曲线对实际聚丙烯酸试样进行测定,结果与粘度法结果相比平均相对误差小于10%。而以PEG为标样,分别采取直接校正和普适校正进行数据处理,结果与粘度法结果相比相对误差大于30%。对于聚羧酸减水剂样品,以上述PAA为标样时,测得分子量分布为2-6；以PEG为标样时,测得分子量分布小于2。根据高分子理论,水溶剂自由基聚合歧化终止得到的产物分子量分布理论值为2-5。因此,以上述PAA为标样,测定聚羧酸减水剂样品分子量及其分布,可以得到较为准确的结果。本标样还用于与PAA具有相似结构的不同阴离子聚电解质分子量及其分布的测定。(3)考察了流动相离子强度,酸度,以及其他色谱条件对PAA凝胶渗透色谱行为的影响。结果表明：流动相离子强度对凝胶基质与PAA样品间的相互作用有较大影响,当流动相离子强度满足一定条件时,保留时间与分子量有较好的线性关系；当流动相pH值为4.75-7.7时,色谱柱与样品的相互作用得到有效抑制。(4)研究发现,用直链结构的PAA标样测定直链结构聚电解质分子量其结果接近真实值,而测定具有长支链梳型结构的聚电解质分子量则存在一定误差。更多还原

【Abstract】 Large error has existed in the determination of the molecular weight and molecular weight distribution of polyelectrolyte by GPC because of the lack of proper standard samples and the non-volume effect. To solve these problems, this paper has done serials work including:(1)PAA oral samples obtained through Solution Free Radical Polymerization with different polymerizing conditions. IR was used to characterize the structure of polymerization products.8 PAA molecular weight standard samples with different molecular weight obtained through twice isothermal precipitation grading method by using dioxane as good solvent, petroleum ether as precipitation. Through the established gradual curve, the average relative error of Mn is only about 7% between this method and viscometry, the average relative error of Mn is only about 9% between this method and end-group titration.(2)The calibration curve can be quickly established by the Mp and its elution volume of the PAA standard samples. For the determination of actual PAA samples, the average relative error is less than 10% by using PAA standard samples. In the contrast, the average relative error is nearly 30% by using PEG as standard samples; for the determination of polycarboxylate superplasticizers, the molecular weight distribution is 2-6 by using PAA standard samples and less than 2 by using PEG as standard samples. Actually, the theoretical value of molecular weight distribution is 2-5 by the disproportionation termination in the Solution Free Radical Polymerization. So a more accurately result can be obtained by using PAA as standard samples. The PAA standard samples in GPC can also be used in the measurement of molecular weight distribution of different anionic polyelectrolyte with similar structure.(3)The influence of the ionic strength、pH and other chromatographic conditions in the determination of PAA in GPC have been investigated. The results showed that the ionic strength had large influence on the adsorption effect between the PAA and gel matrix. A good linear relationship obtained when the ionic strength is in certain extent. The adsorption effect between the PAA and gel matrix is also influenced by the pH. When the pH is 4.75-7.7, the adsorption effect inhibited because PAA is nearly ionization in these acidity.(4)The results show that a great error has existed in the determination of side-chain polyelectrolyte by using PAA standard samples, which has linear chain.And in the determination of the linear-chain polyelectrolyte, the error is not existed.更多还原