聚丙烯酰胺/水溶性酚醛交联反应机理的模拟

Computer Simulations of Cross-linking Reactive Mechanism of Polyacrylamide/resol

采用密度泛函、分子力学和分子动力学等方法从交联反应热力学、动力学等方面研究了聚丙烯酰胺/水溶性酚醛体系的交联机理.以丙酰胺(PA)和(2,4,6)-三羟甲基苯酚(THP)为模型化合物,采用密度泛函方法分别计算了体系中所有可能发生反应的吉布斯自由能和反应能垒.研究结果表明,PA/THP共缩合与THP自缩合反应在热力学上都具有自发性.其中,PA/THP邻位共缩合反应的能垒最小,仅64.54 kJ/mol,因此该反应的活性最大.构建了聚丙烯酰胺/THP体系的交联网络模型,模拟计算得到参予交联反应的—CONH2为其总量的60%.对交联产物进行X射线光电子能谱测试,结果表明,交联产物中仲胺含量与伯胺含量之比约为1.5∶1,从而证实了模拟结果.

The polyacrylamide gel crosslinked by the prepolymer of phenol and formaldehyde is a kind of chemical flooding agent with excellent temperature and salt resistant properties during the enhanced oil reco-very（EOR）.But its cross-linking reactive mechanism is not clear for a long time.In this article,the cross-linking mechanism of polyacrylamide/resol was studied by density-functional theory,molecular mechanic and molecular dynamic methods base on computer simulation.Firstly,propionamide（PA） and 2,4,6-trihydroxy-methylphenol（THP） were looked as model compounds,Gibbs free energy（ΔG） and energy of barrier for transition states involved were calculated by density-functional theory.The results showed that both PA/THP and THP/THP condensation reactions can happen from thermodynamics,while their reaction energies of barrier are different.The energy of barrier for the ortho-position condensation reaction of PA/THP is 64.54 kJ/mol,lowest among the reactions.Secondly,base on the above conclusions,the cross-linking structure of PA/THP was constructed,and found that the reacted -CONH2 is occupied 60% on the total -CONH2 according to the account.At last,the crosslinked products were characterized by X-ray photoelectron spectroscopy.The results show that the numbers ratio of -NH-and -NH2 reached 1.5∶1 in the final products,and validated the results of computer simulation.