| The high shearing rate when pumped into stratums as well as high temperature and high salinity oil reservoirs should be considered for the polymer used in enhanced oil recovery (EOR). In view of this, polymers used for EOR must perform effective thickening properties, temperature and salt tolerance as well as shearing resistance. To explain the thickening properties of copolymer intermolecular, study of the interaction between solution properties and polymer structure is necessary. This dissertation focused on preparation and characterization of microlinked copolymers. In addition, the structure-property relationship is thoroughly discussed.1. A novel water soluble branched copolymer was synthesized by the emulsion copolymerization of acrylamide (AM) with sodium2-acrylamido-2-methylpropane sulfonate (AMPS) using1,3,4,6-tetrahydroxymethylglycoluril (TMGU) as branching agents. The copolymers were characterized by1H-NMR, elemental analyses, light scattering, thermal gravimetric analyses, viscosity, and viscoelastic measurements. The copolymers properly branched had relatively high molecular weight (Mw＞4×106g mol-1) with effective thickening properties, temperature tolerance and resistance to shear force. The copolymer branched by TMGU (the feeding ratio=1mol%) possessed the highest viscosity and viscoelastic modulus as well as good thermal and shearing degradation endurance.2. A novel water soluble branched fluorescent copolymer was synthesized from AM, AMPS and sodium8-((4-vinylbenzyl)oxy)pyrene-1,3,6-trisulfonate using N,N-Methylene-bis-acrylamide (Bis) as branching agents by emulsion copolymerization. The formation of the copolymer was studied by1H-NMR, elemental analyses and static light scattering. Degradation and emission spectra measurements showed that properly branched copolymer (Bis:0.4mol%) with a critical aggregation concentration of0.1g/L in both water and NaCl solutions possessed good temperature tolerance and shearing resistance. Fluorescent intensity of copolymer increased with the increase of temperature while it decreased with the increase of metal ions. Fluorescence quenching induced by Cd2+, Pb2+and Ni2+are static quenching while induced by Zn2+, Cr3+, Co2+and Fe3+are dynamic quenching. The fluorescence quenching capability of Fe3+was more sensitive than other ions indicting its potential use as fluorescent sensor of Fe3+ 3. A novel water soluble branched copolymer was synthesized from AM and AMPS using triethoxy(vinyl)silane modified nano silica as branching agent by emulsion copolymerization. The structure, composition, thermal stability, and molecular weight of these copolymers were characterized by1H-NMR, elemental analyses, thermal gravimetric analyses and light scattering. The solution properties of the copolymers were studied by viscosity measurement. Static light scattering measurements showed that the copolymers had relatively high molecular weight (Mw＞4×106g mol-1). Copolymers with nano silica structure possessed better viscosity properties and degradation resistance than linear polymer. And the optimal feeding weight of modified nano silica was0.10g per mol monomer to obtain the branched copolymer with effective thickening properties, temperature tolerance as well as salt resistance indicting its potential application in enhanced oil recovery.4. A novel weak gel of hydrolyzed polyacrylamide (HPAM) was prepared using inorganic-organic mixed crosslinker. The inorganic crosslinker was aluminum citrate (AlCit), and the organic crosslinker was1,3,4,6-tetrahydroxymethylglycoluril (TMGU). The viscosity measurements showed that the viscosity of HPAM solutions was effectively increased from80mPas to2500mPas in stable state when130mg L-1of AlCit and600mg L-1of TMGU were added, and the gelation time of the weak gel could also be well controlled by changing the concentration of AlCit. Viscoelastic measurements indicted the elastic nature of weak gel. Fourier transform infrared spectra indicated that the carboxyl group of HPAM worked with AlCit while the amino group of HPAM worked with TMGU in the formation of weak gel. Thermogravimetric analyses and viscosity measurement indicted that AlCit may play the major role in the formation of weak gel. The mechanism of the formation of the weak gel was also discussed. The weak gel fabricated with high viscosity may have potential use in oil recovery due to its high viscosity.5. A novel porous super absorbent of P(AA/AMPS) was prepared using Bis and nano silica as crosslinkers. By adjusting monomer feeding ratio and neutralization, water absorption ratio of porous absorbents behaved increase or first increase then decrease with the increase of temperature as increase in pure water. However, water absorption ratio of porous super absorbents behaved increase all along with the increase of temperature as increase in normal saline. It also showed that water absorption rate was effectively increased both in pure water and normal saline while the partical size of super absorbent decreased. The water absorption capacity of porous super absorbents was2200g/g and120g/g at most after60s in pure water and normal saline, respectively. The water-retention rate of super absorbents stayed86%at1MPa afrer4h. The water of hudrogels was also well retented in bentonite dispersion liquid.6. The degradation of hydrolyzed polyacrylamide (HPAM) in solution was studied using pyrogallol. This degradation could be induced without complicated treatments expect adding pyrogallol to HPAM solutions. Moreover, HPAM presented alkaline while progallol autoxidation could be effectively accelerated in alkaline environment. The decrease of apparent viscosity and weight-average molar mass as well as the aggregation radius of HPAM evidently decreased in the degradation procedure. The mechanism of pyrogallol autoxidation was also investigated by UV-vis spectra which indicated that superoxide radical generated in the pyrogallol autoxidation could attract the stone bones inducing the degradation of HPAM. |
PDF Full Text Request