Study On The Synthesis Of Thermally-induced Associative Polymer And Its Solution Performance

Currently,polymer flooding technology is widely used in enhanced oil recovery,however,with the increasing demands in high temperature and high salinity reservoirs,it was reqired to maintain a good thickening ability at such condition.In order to design a kind of polymer which meets the application needs in high temperature and high salinity condition,temperature induced association was introduced to common associative polymer.Using partially hydrolyzed polyacrylamide as main chain,a series of thermal-induced association polymers were developed,meanwhile temperature resistance and salt tolerance of this type of association polymer as well as their influence factors were investigated.The main results were contained in the following sections:Thermosensitive copolymers with lower critical solution temperature(LCST)were prepared by copolymerization of N,N-dimethylacrylamide and diacetone acrylamide through conventional free radical polymerization in water using K2S2O8-Na2SO3 double redox system as an initiator.2-aminoethanethioc was used as chain transfer agent in order to introduce amino end group The thermal responsiveness as well as temperature dependent structure of the copolymer solution were systematically examined through UV-vis spectroscopy,dynamic light scattering(DLS),fluorescence spectrophotometer and 1H NMR.All these results demonstrate that P(DMA-co-DAAM)s with amino-end group exhibit a significant thermal-induced association behavior.At lower temperature P(DMA-co-DAAM)was disolved in the form of unimers while these unimers would transform to micellar aggregates due to the association of hydrophobic segments along the chain at higher temperature.Such phenomenon was ascribed to the change in hydrophilic-hydrophobic balance of DAAM pendant group with increasing in temperature.Further research also implied that the association transition temperature of the copolymer solutions could be effectively regulated by changing NaCl concentration of the solution or the composition and concentration of the copolymers.Lower association transition temperature could be obtained at higher contents of DAAM,which held a well linear relationship in our experiments.The LCST can be easily regulated by change the content of the DAAM in P(DMA-co-DAAM).Thermal-induced association polymers HPAM-g-P(DMA-co-DAAM)were prepared through "graft onto" strategy,thus the peptide coupling between the amino-terminated grafts P(DMA-co-DAAM)and the high molecular weight HPAM backbone was formed with the aid of EDC/NHS.Their molecular structures were characterized by 1H NMR.In comparation with HPAM,steady and dynamic rheological behaviors of HPAM-g-P(DMA-co-DAAM)aqueous solutions were systematically investigated,and their microstructures in aqueous solution were studied by fluorescence probing,and variable temperature 1H NMR.The results showed that:when the grafting ratio was above 0.2mol%,their concentration were above 2.0g/L,it exhibited good thermothickening performance at low shear rate,but this performance disappeared at higher shear rate.It was possible to control the thermothickening properties of the HPAM-g-P(DMA-co-DAAM)by controlling the internal parameters(grafting ratio,side chains length,and side chains' composition)and external parameters(polymer concentration and NaCl concentration).With the increase of the grafting ratio,side chains length,polymer concentration and NaCl concentration,the thermothickening properties of the HPAM-g-P(DMA-co-DAAM)was improved.By varying the feed ratio of DAAM and DMA of the grafts could change the Tass of HPAM-g-P(DMA-co-DAAM)effectively.Fluorescence probing,and variable temperature 1H NMR all confirmed the formation of thermally hydrophobic association of these polymers in high-temperature range.The test of the steady rheological behaviors of HPAM-g-P(DMA-co-DAAM)aqueous solutions showed that:after exceeding the Tass of the polymer,the increase of the viscosity with the temperature growth comes mainly from the increase of the elasticity,this is related to the strength of the polymer chains forming a three-dimensional network structure.In summary,due to adoption of cheaper monomers and excellent tackifying performance the research in this thesis exhibits potential application in market.In another hand the effect of molecular structure and solution condition on the tackifying performance has been comprehensively investigated,which will benifit the design such polymers.