Synthesis Of The CO₂-philic Polycarbosiloxanes By Hydrosilation Method

The design and synthesis of CO₂-philes either in scientific research or in industrial applications is very important,because this kind of polymer can not only be used as a surfactant,dispersant,stabilizer and other substances in the presence of CO₂ as a solvent,but also an important part of the CO₂ separation membrane.Besides,the CO₂-philic polymer is also an essential precursor for CO₂ flooding industry,increasing CO₂ concentration and reducing viscous fingering.Polyether as a kind of CO₂-philes,only in the low molecular weight,it has a certain ability to dissolve in CO₂,limiting its application,so in the field of CO₂–philic polymer,polyether modified objects have been concerned.Some researcher have improved their ability to dissolve in CO₂ by modifying the hydroxyl groups of end group,and in addition to the introduction of CO₂-philic functional groups in polyether side chains or main chains,such as acetate and carbonate groups,can also improve the dissolution capacity.Up to now,polyether modification has focused on the modification of end groups and the improvement of solute-solvent interaction by introducing CO₂-philic groups to improve the solubility of polyethers in CO₂.We intend to graft the Si-O chain to the polyether backbone to improve the solubility of the polyether in CO₂,because of the polymer containing Si-O has a low Tg and low surface tension ?,This indicates that the polymers have good chain flexibility and poor self-interaction.we use hydrosilylation polymerization,synthesized the poly?silyl ether?s copolymer with repeat unit containing different percentages of ether oxygen bonds.The optimum reaction conditions were determined in combination with the physical properties of the starting materials.By measuring the content of catalyst?karstedt?and the effect of temperature on the kinetics of polymerization,we found that the longer the Si-O chain,the faster the rate of polymerization,That is k Si-O10>k Si-O3>k Si-O2.Then,we synthesize the copolymer ofdifferent molecular weights and different structures,measure the CO₂ cloud point pressure,It was found that the cloud point pressure of the poly?silyl ether?s copolymer was much lower than that of the PPO.In addition,we also studied the effect of temperature and molecular weight on the behavior of different modified polymers in CO₂,and found that the higher the temperature and molecular weight,the worse the solubility.On the basis,in order to obtain a polymer with better solubility in CO₂,we designed and synthesized a copolymer of poly?siliyl carbonate?structure in which the PDMS structural unit with relatively good chain stability and low surface tension,and contains a relatively strong solute-solvent interaction with carbonate and CO₂.First,we use the hydrosilylation technique to synthesize 2OH-PDMS-n dihydroxyl monomer,and then we select 1,1'-Carbonyldiimidazole,synthesizing the poly?siliyl carbonate?copolymers through the selection of catalyst and polymerization,and the polysiloxane copolymer with different molecular weight chain containing carbonate structure.In the analysis of polymer solubility,we focused on the three main factors of polymer self-chain flexibility,polymer self-interaction,polymer / CO₂ interaction,and by analyzing the phase behavior of polymers with different topologies in CO₂,we found that chain elongation and surface tension play a key role in CO₂ solubility for structurally different polymers when the molecular weight is relatively large.Finally we have found that when the repeating unit of carbonate content is nearly 9%,we can get the materials with solubility better than PDMS.