Branched Siloxane Modified Poly（Ether-carbonate） And Its CO₂ Thickening Effect

Supercritical carbon dioxide can be used as a fracturing fluid for the production of unconventional petroleum gas.Due to its low viscosity,it brings adverse factors such as "sticky fingering" in the flooding process and affects the flooding efficiency.To solve this problem,an effective thickener needs to be added to supercritical carbon dioxide to increase its viscosity.This project designed a variety of polymers as thickeners,and performed molecular dynamic simulations with Materials Studio software.In the second chapter,straight chain Poly（ether-carbonate）（PEC）was designed and synthesized by ring opening copolymerization in autoclave.In the chain,organosilicon monomer SAGE（product labeled PEC-SAGE）was introduced,styrene oxide（SO）and SAGE introduced product is labeled as PEC-SAGE-SO.The results of molecular dynamics simulation show that a small amount of SAGE can reduce the interaction between polymer molecules,and the interaction between polymer molecules and carbon dioxide molecules.From the experimental results,the introduction of SAGE into PEC will reduce the cloud point pressure,which is especially obvious when PEC-SO polymer is introduced into SAGE.According to the thickening effect of Poly（ether-carbonate）on carbon dioxide,the thickening effect of PEC-SAGE-SO is 5 times that of PEC-SAGE.In the third chapter,TPA-PEC,TMA-PEC and TFA-PEC were synthesized by ring opening copolymerization with TPA,TMA and TFA as initiators,respectively.Through cloud point pressure experiment and carbon dioxide thickening experiment,the effects of different chain numbers of the copolymers with phenyl as the center on the solubility and thickening properties of the products in carbon dioxide were analyzed and compared.The results show that TFA-PEC has the worst solubility in carbon dioxide,but the most prominent thickening effect.The results of molecular dynamics simulation show that the interaction between TPA-PEC and CO2 is stronger,the interaction between polymer chains is stronger,and the interaction between TMA-PEC polymer chains is weaker.In the cloud point pressure data,TPA-PEC has the best solubility in carbon dioxide.TFA-PEC-SAGE combines excellent solubility and thickening properties.In the fourth chapter,the solubility energy of the polymer in CO2 and the simulation results show that the affinity of the hyperbranched polysiloxane to CO2 is better than that of the straight chain structure.The content of hyperbranched polysiloxane in CI2 is 1 wt%～3 wt%,and the cloud point pressure rise is not obvious which lays the foundation for the hyperbranched polymer to be used in CO2 thickening.In MD results,HbSiO-Phen has lower CED and δ values than HbSiO-KH and meth-Phen-SiO,which is favorable for dissolution in CO₂.