Preparation of Star Hydrophobically Associated Water-Soluble Polymers by SET-LRP

Zhou Xiaowan*, Ding Wei, Yang Lingxue, Li Zhendong

(Key Laboratory of Petroleum and Natural Gas Chemistry, College of Chemistry and Chemical Engineering, Northeast Petroleum University, Daqing 163318)

Abstract: Star-shaped Hydrophobically Associating Water-soluble Polymer (P(AM/NtBA/NaAMPS)) was prepared by single electron transfer living radical polymerization (SET-LRP) with acrylamide (AM), sodium 2-acrylamido-2-methylpropane sulfonate (NaAMPS) and N-tert-butylacrylamide (NtBA) as comonomer, Cu0 powder and Me6-TREN as catalytic system and CCl4 as multifunctional initiator. Effects of the initiation on temperature, hydrophobic monomer dosage, AMPS dosage, initiator dosage, catalyst dosage and monomer concentration on molecule weights are investigated by control variable method. The optimum synthesesis conditions were determined and the solution properties were investigated. The results show that as the acrylamide (AM) content is 93.6% (mol) in total monomer, 2-acrylamide-2-methylprop contents of anesulfonic acid (AMPS) 5%, N-tert-butylacrylamide (NtBA) 1.4%. And as the monomer concentration is 35%, there action temperature is 25.0 ℃, the mass fraction of initiator is 0.4942%, the amount of catalyst is 0.0848%, the deactivation agent is 0.1192%, the maximum molecular weight to the star-shaped hydrophobically associating water-soluble polymer can reach up to 2.67 * 106. The polymer have temperature resistance and salt to tolerance, and the solution property of star-shaped hydrophobically associating water-soluble polymers was similar to the line-shaped polymer. In addition, the effect of CaCl2 on the apparent viscosity of the hydrophobically associating polyacrylamide was more significant than NaCl.

Keywords：single electron transfer living radical polymerization； star shaped hydrophobically N-tert-butyl acrylamide；temperature resistance and salt

Single Electron Transfer Active Radical Polymerization (SET-LRP) [1] is a new method of active radical polymerization. Compared with the previous methods of polymer synthesis, this method has the advantages of being able to carry out at low temperature[2], having less influence on product color, less catalyst dosage[3,4], rapid polymerization rate, and so on. Ultra-high molecular weight polymers with narrow molecular weight distribution can be obtained, and the molecular weight distribution can be well controlled and the perfect functionalized chain ends[5,6] can be retained. The preparation of hydrophobically associating water-soluble polymers by this method not only overcomes the problems of uncontrollable reaction, complex reaction and high cost caused by macromolecule reaction, but also solves a series of problems such as complex post-treatment process and chain transfer reaction caused by a large number of surfactants in micellar polymerization. ET-LRP method has become a research hotspot in the field of living radical polymerization.

Water-soluble hydrophobic associative polymers are water-soluble polymers with a small amount of hydrophobic groups on the macromolecular chain of hydrophilic polymers. In aqueous solution, the hydrophobic groups of polymer aggregate due to hydrophobic action. With the change of the content of hydrophobic monomer and concentration of solution in polymer, the intramolecular and intermolecular association of macromolecular chains can be shown, which makes polymer have unique solution properties[8-10], so it is widely used in the tertiary oil recovery of oilfields. However, most of the studies at home and abroad are long-chain comb-like structures, and there are few studies on star-like hydrophobically associating water-soluble polymers. Compared with traditional linear polymers, star polymers have the characteristics of high solubility, low crystallinity, small hydrodynamic volume and high density functional group distribution[11,12]. By changing the branching degree, the physical and chemical properties of the polymer can be well controlled, which is more conducive to the processing and modification of high molecular weight polymers at lower temperatures[13]. It provides a better advantage for the development of new hydrophobically associative water-soluble polymers with good temperature and salt resistance, and also for star-shaped polymer molecules. The branched structure of hydrophobic associating polymer can increase the intramolecular association and the molecular conformation is relatively contracted. Therefore, it can effectively improve the injectability of hydrophobic associating polymer in theory [14]. At present, there are few reports on the application of SET-LRP method in the synthesis of star hydrophobically associating acrylamide water-soluble polymers, which has broad research prospects. So in this experiment, N-tert-butyl acrylamide (NtBA) was used as hydrophobic monomer, acrylamide (AM) was used as hydrophilic monomer, and AMPS with strong anionic group was introduced to synthesize a star-shaped hydrophobically associative water-soluble polymer, because the molecular chain of the copolymer contained side groups of branched chain structure and strong anion. Ionic groups make the polymer have good water solubility, temperature resistance and salt resistance.

1 Experimental section

1.1 Reagents and Instruments

Acrylamide (Zhejiang Xinyong Chemical Co., Ltd.), chemical purity; N-tert-butyl acrylamide (Shanghai Aladdin Chemical Reagent Factory), 2-acrylamide-2-methylpropionic sulfonic acid (Shanghai Aladdin Chemical Reagent Factory), tri (2-dimethylaminoethyl) amine (Alfaesa (China) Chemical Co., Ltd.). Carbon tetrachloride (Zhengzhou Chemical Reagent Plant 3), copper chloride (China Tianjin Basf Chemical Co., Ltd.), copper powder, sodium chloride, calcium chloride, sodium hydroxide, acetone, anhydrous ethanol: all purchased from Tianjin Damao Chemical Reagent Plant; self-made secondary distilled water. High Purity Nitrogen (Daqing Xuelong Gas Co., Ltd.); Bruker-Tensor 27 Fourier Transform Infrared Spectrometer (Bruker Company, Germany), KBr Press; DZG-6020 Vacuum Dryer; JY-02 Multifunctional Crusher; DK-S24 Constant Warm water bath; Electronic analytical balance; Brinell viscometer; Glass constant temperature water bath; Non-diluting Ubbelohde viscometer, according to GB12005.1-89, inner diameter 0.4 mm.

1.2 SET-LRT of P(AM/NtBA/NaAMPS)

1.2.1P(AM/NtBA/NaAMPS) was synthesized by mixing AMPS into aqueous solution, which was cooled in ice bath and slowly adding 20% sodium hydroxide solution of equal molar ratio to the solution while stirring. The neutralization reaction lasted for 2 hours to obtain NaAMPS solution. A certain amount of N-tert-butyl acrylamide was dissolved in acrylamide aqueous solution under rapid stirring, and then poured into the reaction bottle with magnetic stirrer. Then a certain amount of monomer (NaAMPS), catalyst (Cu), inactivator (CuCl2) was added, and a certain amount of solvent water was added. The reaction bottle was placed in a constant temperature water bath, and the oxygen in the system was removed by adding high purity nitrogen for 15 minutes. Then, in nitrogen atmosphere, a suitable amount of ligand Me6-TREN and initiator CCl4 were added into the micro-sampler, and the reaction bottle was sealed quickly after the polymerization reaction took place. The reaction products were slowly poured into excessive acetone and precipitated with white precipitation. The unreacted Cu0 powder and divalent copper complex were removed by neutral Al2O3 column. The product was soaked in anhydrous ethanol and dried in vacuum drying chamber at 40℃. The conversion rate was calculated and crushed into powder for later use. According to GB12005.1-89, the relative molecular weight was measured by Ubbelohde viscometer. The synthetic reaction was shown in Fig. 1.    

      Figure 1 Synthesisof P(AM/NtBA/NaAMPS)

1.2.2 Polymerization mechanism of P(AM/NtBA/NaAMPS). As shown in Figs 2 and 3, the SET-LRP polymer is essentially a balancing process between active and resting substances. The zero-valent monomer reacts with the halogen-containing initiator CCl4 by redox reaction. The initiator CCl4 obtains electrons and then becomes an ionized self-base intermediate. It is unusual to think that the real self-base generates displaced carbon atoms, and zero-valence reacts with the generated displaced carbon atoms. Carbon and quaternary carbon, and then initiate the polymerization of reaction monomers. Since the final free radicals are Quaternary carbon, the polymer synthesized is star-shaped polymer. CuCl/L produced is decomposed in polar solvents to form active agents Cu0 and chemical agents CuCl2/L, while CuCl2/L passivates the generated free radicals. The reaction makes the free radical combine with Cl atom, and produces CuCl/L and resting seed Pn-X, while the disproportionated Cu0 is connected with catalytic polymerization, thus realizing the feasibility of polymerization [15,16].

Figure 2 Catalytic cycles in SET-LRP

Figure 3 Elementary reactions of Cu(0)-catalyzed SET-LRP

1.3 Determination of Monomer Conversion Rate

In this experiment, the conversion of monomers was measured by weight calculation method. Samples were taken out at a predetermined reaction time (45 minutes). Reaction products were slowly poured into excessive cold acetone and precipitated in white. The unreacted Cu0 powder and bivalent copper complex were removed by neutral Al2O3 column. After repeated washing with anhydrous ethanol, the filtered products were put into vacuum drying chamber. Dry until the sample is of constant weight. The formulas for calculating monomer conversion are as follows:

Conversion (C)= (polymer/monomer mass)*100%

The highest yield of star polymer P(AM/NtBA/NaAMPS) can reach 90%.

1.4 P（AM/NTBA/NAAMPS）Performance testing

1.4.1 Temperature resistance. Firstly, linear P(AM/NtBA/NaAMPS) was synthesized by free radical micelle polymerization. Then, star P(AM/NtBA/NaAMPS) and linear P(AM/NtBA/NaAMPS) were prepared into 15, respectively. The apparent viscosity of the polymer was measured by Brinell viscometer in the solution of 00mg/L at 25-75 ℃.

1.4.2 Salt resistance. Star type P(AM/NtBA/NaAMPS) was dissolved in 1000 mg/L, 3000 mg/L, 5000 mg/L, 7000 mg/L and 9000 mg/L salt solution respectively, and then 1500 mg/L was prepared. The apparent viscosity of polymer solution was measured at 25℃and compared with that of linear P(AM/NtBA/NaAMPS) solution under the same conditions.

2 Results and discussion

2.1Structural characterization of the products

Star hydrophobically associative water-soluble P(AM/NtBA/NaAMPS) was synthesized by the experimental method described in 1.2.1. The structure of star P(AM/NtBA/NaAMPS) was characterized by FT-IR and 1H-NMR. The results are shown in Fig. 4 and Fig. 5.

Figure 4 FT-IR spectrum of Star-shaped-P(AM/NtBA/NaAMPS)

It can be seen from Fig 4 that the peak at 1650 cm-1 is a typical C=O stretching vibration peak in amide I band; a broad peak at 3435 cm-1 belongs to-NH-absorption peak; the peak at 2930 cm-1 is C-H stretching vibration peak of methylene; and the peak at 1448 cm-1 is C-H stretching vibration peak. The characteristic absorption band of - C(CH3)3 at 1385 cm-1 and 1365 cm-1 proves the existence of hydrophilic amide grouP(-CONH2) and hydrophobic tert-butyl-C(CH3)3. In addition, the characteristic peaks of sulfonic groups appeared at 1157 cm-1, and the peaks at 1119 cm-1 and 1069 cm-1 is Skeleton vibration peak of , and the peaks at 546cm-1 is the absorption peaks of C-Cl. According to the structure of the characteristic peaks mentioned above, the synthesized products have the characteristics of target products.

Figure 5 1H-NMR spectrum of Star-shaped-P(AM/NtBA/NaAMPS)

Fig. 5 is a 1H-NMR diagram of star P(AM/NtBA/NaAMPS). The proton peaks of solvent CDCl3 are at δ value of 7.29; the proton peaks of –CH- and- CH2- occur at δ 1.38-1.60 ppm in the polymer main chain; the proton peaks of CH3 in the NtBA branched chain occur at 1.27 ppm, and those of -CH3 in the AMPS branched chain. The sub-peaks occur at 0.90 ppm. The electron cloud density around the proton decreases, the shielding effect weakens and the proton peak moves to the low field due to the influence of the end groups of –CH-and-CH2-on the main chain of the polymer. Therefore, δ value of 1.90 ppm is the proton signal peak of -CH2- affected by Cl-. The proton peak shifts to low field under the influence of Cl terminal group, and δ value 2.06 ppm is the proton signal peak of CH; δ value of 5.78 ppm is the signal peak of -NH2 on AM chain, and 6.17ppmh is the proton peak of –NH-, so it can be seen that all three monomers are aggregated. At the same time, the polymer contains -Cl terminal group, which indicates that the polymerization reaction is active.

Therefore, according to the synthetic results of infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy, star-shaped P(AM/NtBA/NaAMPS) was synthesized as the target product.

2.2 Effect of Reaction Conditions on Polymerization

2.2.1 Initiation temperature affects the polymerization reaction. Firstly, the initial material ratio is fixed as n(AM):n(Cu):n(CuCl2):n(Me6-TERN):n(CCl4)=674.5:0.75:0.5:0.85:1.8.Set the molar ratio of AM with AMPS and NtBA is 93.6%:5%:1.4% and the monomer concentration is 35%. The effect of initiation temperature on the molecular weight of polymer is studied. The results are shown in Table 1.

From Table 1, it can be seen that the relative molecular mass of star polymer P(AM/NtBA/NaAMPS) increases gradually with the increase of initiation temperature. When the temperature reaches 25 ℃, the relative molecular mass reaches the maximum, which can reach 2.67 million. As the temperature continues to rise, the relative molecular weight shows a downward trend, so the optimum initiation temperature for this polymerization is determined to be 25 ℃. This is due to the influence of reaction temperature on the activity of initiator in polymerization. When the temperature is too low, the activity of initiator is low, the number of free radicals is small, and the activity is not high. With the increase of temperature, the rate of free radical formation from Cl atom captured by Cu0 from C-Cl bond is accelerated, the reaction rate constant of chain growth is increased, the monomer conversion rate is increased, and the relative molecular weight is increased. However, the high temperature results in the rapid formation of free radicals in a short time and the increasing concentration of free radicals. Under certain conditions of monomers, the length of the kinetic chain becomes shorter, the reaction rate speeds up, the reaction is too violent, or even explosive polymerization. At the same time, the chain transfer and chain termination reactions between free radicals increase, which ultimately leads to the molecular weight of polymers is not large enough. 。

2.2.2 Effect of Hydrophobic Monomer Content on Polymerization: Firstly, the initial material ratio is fixed as n(AM):n(Cu):n(CuCl2):n(Me6-TERN):n(CCl4) =674.5:0.75:0.5:0.85:1.8. Setting The molar ratio of AMPS content to total monomer content is 5%, monomer concentration is 35%, reaction temperature is 25 ℃. The effect of hydrophobic monomer content on the relative molecular weight of star polymer is studied. The results are shown in Fig. 6.

Figure 6 Effective of the content of hydrophobic monomer on the relative molecular weight

The solubility and relative molecular mass of star hydrophobically associating water-soluble polymer P(AM/NtBA/NaAMPS) are greatly influenced by the content of hydrophobic monomers. When the dosage of hydrophobic monomer NtBA is low, the hydrophobic units in polymer molecular chains are few, which is not conducive to hydrophobic association between molecules, and the molecular weight of polymer is low. With the increase of the ratio of hydrophobic monomer NtBA, the content of hydrophobic units in polymer structure is also increasing, and the relative molecules of star polymer are also increasing. When the molar ratio of hydrophobic monomer NtBA to total monomer reaches 1.4% mol, the relative molecular weight of NtBA reaches its maximum value. If the content of hydrophobic monomer continues to increase, the hydrophobic units increase, resulting in poor solubility of polymer and smaller relative molecular weight. This is due to the excessive content of hydrophobic units in the obtained polymer molecular chains and the increase of side groups containing branched chains, which is not conducive to the polymerization process, resulting in the decrease of polymer molecular weight, poor water solubility and even insolubility in water, thus losing the viscosifying effect on water. Therefore, the molar fraction of hydrophobic monomer NtBA should be 1.4%.

The influence of 2.2.3 AMPS content on the polymerization reaction is the same as the initial material ratio. The molar ratio of NtBA content to the total monomer content is 1.4%, monomer concentration is 35%, reaction temperature is 25 ℃. The influence of AMPS content on the relative molecular weight of polymer is studied. The results are shown in Figure 7.

It can be seen from Fig. 7 that the relative molecular mass of star polymer increases with the increase of AMPS content; when the molar ratio of AMPS reaches 5%, the relative molecular mass of polymer reaches its maximum value; and when the molar ratio of AMPS continues to increase, the relative molecular mass of star polymer decreases gradually. This is because there is a huge side group on the AMPS chain, SO3H, which increases the steric hindrance and enhances the hydrolysis resistance. In addition, the - SO3H group is a strong polar group. Its strong electrostatic repulsion and hydrophilicity make the polymer water-soluble. With the increase of AMPS content, the electrostatic repulsion force produced by ionization in aqueous solution becomes larger, which makes the polymer more extensible in aqueous solution, and the relative molecular weight becomes larger. However, when the content of AMPS is more than 5%, the AMPS structural unit at the end of the molecular chain will prevent the unreacted AMPS monomer from open-chain polymerization due to the strong electrostatic repulsion of AMPS itself. In addition, the larger steric hindrance of AMPS chains makes the monomer polymerization difficult and the molecular weight reduced. Therefore, the appropriate amount of AMPS is 5%.

2.2.4 The influence of initiator dosage on the polymerization reaction was the same as that of initial material ratio. The molar ratio of AM to AMPS and NtBA monomers was 93.6%:5%:1.4%, monomer concentration was 35%, reaction temperature was 25 ℃. The effect of initiator dosage on polymer phase was studied. The effect on molecular mass is shown in Fig. 8.

Figure 7 Effective of the content of AMPS ontherelative molecular weight

Figure 8 Effect of the initiator dosage on there relative molecular weight

It can be seen from the figure that the relative molecular weight of star polymer P(AM/NtBA/NaAMPS) increases gradually with the increase of initiator dosage. When the initiator dosage reaches 77.5 ugL (8.03 *10-4 mol), the relative molecular weight reaches the maximum, and with the increase of initiator dosage, the relative molecular weight of star polymer P(AM/NtBA/NaAMPS) reaches the maximum. Relative molecular weight of the product decreased with the addition of 2. The reason for this phenomenon is that when the dosage of initiator is low, less free radicals are produced in the system, which affects the reaction. With the increase of initiator dosage, the concentration of active species in the system increases, the concentration of free radicals increases, and then the conversion of monomers in unit time increases, and the reaction rate accelerates. However, when the concentration of monomers is constant, the amount of initiator continues to increase, which will make the monomers linked to each active species. When the number of subunits decreases, the relative molecular weight decreases. Therefore, the dosage of initiator should be 8.03 x 10-4 mol.

2.2.5 The molar ratio of AM to AMPS and NtBA was 93.6%:5%:1.4%. The monomer concentration was 35%. The reaction temperature was 25 ℃. The effect of the amount of catalyst copper on the molecular weight of polymer was studied. The results are shown in Figure 9.

It can be seen from the figure that the relative molecular weight of star polymer P(AM/NtBA/NaAMPS) tends to increase with the increase of copper content in the catalyst. When the amount of catalyst reaches 0.0212g, the molecular weight of star polymer P(AM/NtBA/NaAMPS) reaches its maximum value. With the continuous addition of copper powder, the relative molecular weight showed a downward trend. This is because the activation process of SET-LRP is carried out on the surface of copper powder. Increasing the mass of SET-LRP is equivalent to increasing the surface area, accelerating the activation process of the system, increasing the concentration of active free radicals, more reactive chains in the state of active chains, and increasing the molecular weight by continuous polymerization. With the increase of copper powder, the concentration of free radicals produced in the initial stage of polymerization also increased. The in-situ formation of copper (II) was not enough to passivate all free radicals. The side reactions such as chain transfer between free radicals and chain termination increased, which resulted in the low molecular weight. Therefore, the appropriate amount of copper powder is 0.0212g.

Figure 9 Effect of dosage of the copper catalyst to the relative molecular weight

2.2.6 Monomer Concentration Affects Polymerization Initial Material Ratio Same as above. The molar ratio of AM to AMPS and NtBA is 93.6%:5%:1.4% and the reaction temperature is 25 ℃. The effect of monomer concentration on the relative molecular weight of polymer is studied. The results are shown in Fig 10 as follows:

Figure 10 Effectof hemonomer concentration on the relative molecular weight

It can be seen from the figure that the relative molecular mass of star polymer P(AM/NtBA/NaAMPS) increases first and then decreases with the increase of monomer concentration. When the concentration of monomer is 35%, the relative molecular mass of the system reaches its maximum. This is because with the increase of monomer concentration in the reaction system, the contact and collision probability of reactants increase, the time of gel effect becomes shorter, the polymerization rate becomes faster, the chain reaction rate constant increases, and the viscosity and molecular weight of the system increase. As the monomer concentration continues to increase, the heat released from the polymerization reaction is not easy to lose, the chain growth and chain termination rate become larger, the chain growth time becomes shorter, and thus the relative molecular weight decreases. Therefore, the optimum monomer concentration in this experiment is 35%.

2.3 Performance Test of Star Polymer P(AM/NtBA/NaAMPS)

2.3.1The effect of temperature on the apparent viscosity of polymer solution was studied. Star and linear P(AM/NtBA/NaAMPS) solutions of 1500 mg/L were prepared with shear rate of 6s-1. The apparent viscosity of polymer solution was measured at 25 to 75 ℃. The experimental results are shown in Fig. 11.

Figure 11 Polymer apparent viscosity curve of the change temperature

Temperature has two main effects on the apparent viscosity of hydrophobically associating P(AM/NtBA/NaAMPS). One is that increasing temperature increases the entropy of P(AM/NtBA/NaAMPS) solution system and increases the hydrophobic association, which is defined as a "positive effect". The other is that increasing temperature increases the apparent viscosity of P(AM/NtBA/NaAMPS) solution. The thermal movement of hydrophobic groups in polymers is accelerated, and the hydrophobic association between molecules is weakened, which is called "negative effect"[17]. As can be seen from Fig. 11, the thermal resistance of star-shaped polymer P(AM/NtBA/NaAMPS) solution is similar to that of linear polymer, and the apparent viscosity of star-shaped polymer at the same concentration is slightly higher than that of linear polymer. Star-shaped hydrophobic associative polymerization occurs at 25 to 75 ℃. The viscosity retention rate of the polymer is 57.34%, while that of the linear polymer is 53.37%. The apparent viscosity of the two kinds of polymers decreases slightly with the increase of temperature when the temperature is lower than 45 ℃. At this time, the apparent viscosity of the polymer solution changes little when the positive and negative effects are combined. When the temperature is higher than 45 ℃, the negative effect is greater than the positive effect. Finally, the apparent viscosity of the two solutions decreases with the increase of temperature. When the temperature is higher than 55 ℃, the apparent viscosity of P(AM/NtBA/NaAMPS) decreases slowly with the increase of temperature.

2.3.2 Effects of NaCl and CaCl2 Concentrations on the Apparent Viscosity of Polymer Solutions Preparation of Polymer Solutions Containing Different Concentrations of NaCl and CaCl2 at Shear Rate of 6s-1. The variation of NaCl and CaCl2 Concentrations on Star and Linear P(AM/NtBA/NaAMPS) ) The effect of the apparent viscosity of the solution is shown in Fig 12 and 13.

As can be seen from Fig 12 and 13, with the increase of salt concentration, the apparent viscosity of star polymer P(AM/NtBA/NaAMPS) and linear P(AM/NtBA/NaAMPS) solutions gradually decreases and then tends to be flat. This is because both polymers contain polar anionic monomers. When salt is added to the polymer solution, the negative charges on the molecular chain are shielded, the electrostatic repulsion between the polymer ions is weakened, and the molecular chain is curled. However, when the salt concentration in the solution is too high, the intermolecular cooperation will occur. The volume shrinkage of the supramolecular structure formed in the polymer is greatly enhanced, the hydrodynamic volume of the solution is reduced, and the apparent viscosity of the polymer is reduced. At the same time, it can be seen from the two figures that the salt resistance of the two kinds of polymer solutions is similar, but the apparent viscosity of star-shaped P(AM/NtBA/NaAMPS) is slightly higher than that of the linear polymer. This may be due to the better rigidity and orderly molecular structure of star-shaped polymer main chains, and the increase of the apparent viscosity of star-shaped P(AM/NtBA/NaAMPS). The rotational hydraulic radius of the molecular chain is increased, and the probability of curling of the molecular chain is reduced. At the same salt concentration, the apparent viscosity of polymer solution with CaCl2 is lower than that with NaCl. This is because the higher the valence of metal ions, the greater the decrease of_potential, so the effect of calcium ions on the apparent viscosity of polymer is greater than that of sodium ions.

3 Conclusion

(1) Using SET-LRP method, acrylamide (AM), sodium 2-acrylamide-2-methylpropionate sulfonate (NaAMPS) as hydrophilic monomer, N-tert-butyl acrylamide (NtBA) as hydrophobic monomer, Cu0 powder/tri (2-dimethylaminoethyl) amine (Me6-dimethylaminoethyl) as hydrophobic monomer. Star hydrophobically associating water-soluble polymer P(AM/NtBA/NaAMPS) was synthesized by using TREN as catalyst, hydrogen peroxide as solvent, CCl4 as initiator and CuCl2 as passivator. The product was analyzed by infrared spectroscopy and proved to be the target product.

Figure 12 Influence of NaCl solution Concentration on polymer apparent viscosity

Figure 13 Influence of CaCl2 solution concentration on polymer apparent viscosity

(2) The effects of temperature, hydrophobic monomer content, AMPS content, initiator dosage, catalyst copper and monomer concentration on the relative molecular weight of star hydrophobic associative water-soluble polymer P(AM/NtBA/NaAMPS) were investigated by controlling variable method. The optimum synthetic conditions of star hydrophobically associating water-soluble polymer P(AM/NtBA/NaAMPS) were determined as follows: initiation temperature 25 ℃, monomer concentration 35%, initiator mass fraction 0.4942%, catalyst copper mass fraction 0.0848%, passivator mass fraction 0.0848%. When AM, AMPS and NtBA accounted for 93.6%, 5% and 1.4% (molar ratio) of the total monomers respectively, the relative molecular weight of star polymer P(AM/NtBA/NaAMPS) reached the maximum of 2.67 million.

(3) The solution of star hydrophobically associating water-soluble polymer P(AM/NtBA/NaAMPS) synthesized by SET-LRP method has a certain temperature and salt resistance, and its performance is similar to that of linear P(AM/NtBA/NaAMPS) solution and CaC at the same concentration. The effect of L2 on the apparent viscosity of P(AM/NtBA/NaAMPS) is greater than that of NaCl.

Reference:

[1] PercecV, Guliashvili T, Ladislaw J S, et al. J Am Chem Soc, 2006, 128:14156-14165.

[2] Lligadas G, Ladislaw J S, Guliashvili T, etal. J Polym Sci Part A: Polym Chem, 2008, 46 (1): 278-288.

[3] Matyjaszewski K, Pintauer T, Gaynor S. Macromolecules, 2000, 33(4): 1476-1478.

[4] Ydens I, Moins S, Botteman F, et al. E-Polymers, 2004, 39:1-7.

[5] Lligadas G, Percec V. J Polym Sci Part A: Polym Chem, 2007, 45 (20): 4684-4695.

[6] Aksakal R, Resmini M, Becer C R. Polym Chem, 2015, 7 (1): 171-175.

[7] Zhang Huaiping, Xu Kai, Cao Xianfu, et al. Petrochemical Industry, 2006, 35 (7): 695-700.

[8] Lara-Ceniceros T E, Cadenas-Pliego G, Rivera-Vallejo C C, et al. J Polym Res, 2014, 21(7): 1-12.

[9] Yahaya G O, Ahdab A A, Ali S A, et al. Polymer, 2001, 42:3363-3372.

[10] Guo Navy, Hu Xingqi, Wang Liang, et al. Progress in Chemical Industry, 2003, 22 (12): 1312-1315.

[11] Xuanj, Rosen B M, Percec V. J Polym Sci Part A: Polym Chem, 2010, 48: 2716-2721.

[12] Ohno S, Gao H, Cusick B, et al. Macromol Chem Phys, 2009, 210:421-430.

[13] Moschogianni P, Pispas S, Hadjichristidis N.J Polym Sci Part A: Polym Chem, 2001, 39 (5): 650-655.

[14] Wang Fuxiao, Duan Ming, Fang Shenwen, et al. Petrochemical Industry, 2010, 3 (95): 537-541.

[15] Ding W, Lv C, Sun Y, et al. J Polym Sci Part A: Polym Chem, 2010, 49 (2): 432-440.

[16] Ding Wei, Zhao Nana, Liu Kang, et al. Science and Engineering of Polymer Materials, 2015 (5): 9-13.

[17] Jiang Chunyong, Duan Ming, Fang Shenwen, et al. Petrochemical Industry, 2010, 39 (2): 204-208.

This translation was done for the cheater- an translaiton translation agency: [email protected]