基于醛基化改性的交联聚苯乙烯微球制备席夫碱型螯合树脂的研究

在缚酸剂Na2CO3存在下,使溶胀的氯甲基化交联聚苯乙烯(CMCPS)微球表面的氯甲基与对羟基苯甲醛(HBA)发生亲核取代反应,制得了醛基(AL)化改性的交联聚苯乙烯(ALCPS)微球;利用所制得的ALCPS微球与甘氨酸(GL)发生缩合反应,制备了同时含有席夫碱配基与羧基的席夫碱型螯合树脂AGCPS微球。采用红外光谱法表征了微球功能基团的结构变化,重点研究了CMCPS微球醛基化改性反应,考察了影响亲核取代反应的主要因素,推测和探讨了反应的机理。研究表明,CMCPS微球表面的苄氯基团与HBA缩合反应的速率与HBA的浓度无关,属于典型的SN1反应;使用极性较强的溶剂DMF,在较高的反应温度(90℃)下,有利于亲核取代反应的进行。所得席夫碱型螯合树脂对铜离子具有较强的螯合吸附能力。

Studies on the Preparation of Schiff Base-Type Chelating Resin Based on Aldehyde Group-modified Crosslinked Polystyrene Microspheres

The nucleophilic substitution reaction between the chloromethyl groups of the swelled CMCPS microspheres and p-hydroxybenzaldehyde(HBA) was first allowed to be carried out in the presence of acid-acceptor Na2CO3,obtaining aldehyde(AL) group-modified CPS(ALCPS) microspheres.The Schiff base reaction between ALCPS microspheres and glycine(GL) was conducted,resulting in Schiff base-type chelating resin,AGCPS,where Schiff base ligand and carboxyl group exist at the same time.Its chemical structure was characterized by infrared spectrum.The aldehyde group-modification reaction of CMCPS was mainly investigated,the effects of main factors on the substitution reaction were examined,and the reaction mechanism was speculated and explored.The experimental results showed that the rate of the nucleophilic substitution reaction is independent of the concentration of the nucleophile HBA,indicating that this is a typical unimolecular nucleophilic substitution reaction i.e.SN1.The solvent polarity is favourable for the fracture of C—Cl bond of the benzyl chloride group,and can accelerate the substitution reaction.The increase of the reaction temperature is also advantageous to the substitution reaction.DMF is a suitable solvent and 90℃ is an appropriate temperature.The prepared AGCPS resin possesses stronger chelating ability for transition metal ions.