Using a Brush Copolymer as Efficient Dispersant for the Preparation of Highly Stabilized Ag Nanoparticles in Aqueous Suspensions
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Abstract Silver (Ag) nanoparticle has extremely high surface energy and it is difficult to find an efficient dispersant to prevent its agglomeration in suspensions. A new brush copolymer, succinic anhydride modified epoxy‐amine poly[(propylene oxide)‐ co ‐(ethylene oxide)]‐grafted polymer (EPOA), which can efficiently disperse concentrated aqueous suspensions of Ag nanoparticles is revealed. The dispersion efficiency of EPOA for the dispersion of a 60 nm‐Ag nanoparticles in aqueous suspension is studied by measuring its sedimentation and rheological behavior, and the results are compared with those of a commercially available dispersant, ammonium poly(acrylic acid) (PAA‐NH 4 ). Interactions between the dispersants and the Ag nanoparticles are characterized by zeta potential and adsorption analyses. Theoretical calculations are conducted to clarify the adsorption and the dominant dispersion stabilization mechanisms of the dispersants. Compared with PAA‐NH 4 , EPOA obtains a higher stable suspension of Ag nanoparticles with less significant sedimentation over 1 month. The dispersion homogeneity of the suspension remains excellent even at an extremely high solid loading of 30–40 wt%. According to adsorption analysis, it is suggested that both EPOA and PAA‐NH 4 adsorb via single‐point attachment through the carboxyl group on the Ag surface. Based on theoretical calculations, the Ag nanoparticles are better stabilized by EPOA via an electrosteric dispersion mechanism.Keywords:
Zeta potential
Dispersion stability
Acrylic acid
Suspension
Silver nanoparticle
The interaction between CaCl 2 and double hydrophilic block copolymer, poly(ethylene oxide) 45- block-poly(acrylic acid) 70, PEO 45- b-PAA 70, was investigated. At a stoichiometric ratio of Ca2+:COO (-) = 0.5, Ca2+ ions were bound to COO (-) groups on PAA segments via electrostatic interaction. Small particles of 4-8 nm in diameter were observed, suggesting the formation of coil-like polymeric globule induced by charge neutralization. At Ca2+:COO (-) >or= 2.5, monodispersed aggregates of average hydrodynamic diameter of 52.0 +/- 7.4 nm were produced. The ISE, ITC, surface tension and fluorescence spectroscopic data confirmed that the formation of these aggregates is not the result of interaction between excess Ca2+ ions and the polymer, but rather it is due to changes in the water activity that triggers the structural rearrangement of Ca2+/PEO 45- b-PAA 70 complex.
Acrylic acid
Stoichiometry
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In various industrial processes such as wet shape forming of ceramics, particles are usually applied in a slurry. In such processes, adding the appropriate amount of dispersant to the slurry is important for the production of better products. The adsorption of dispersant onto the particle surface is an important factor ; hence, many researchers have reported this phenomenon. However, few researchers have studied the effect of adsorption conformation of dispersant on dispersion stability. We investigated the effect of adsorption conformation of ammonium polycarboxylate, an adsorbed anionic polymeric dispersant with a molecular mass of 8000～10000, onto alumina. In this paper, several results of our recent research, such as the effects of additive amount of dispersant, dissolution of ion in the slurry, and effect of time at which dispersant conformation changes on dispersion stability of the slurry, are introduced.
Dispersion stability
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The effects of three dispersants(PVP,Triammonium citrate,β-Alanine) on the stability of ITO suspension prepared by ball milling dispersion were studied.The influences of dispersing time and dispersant content on stability of ITO suspension were investigated.And the roles of the different dispersant and their dispersing mechanism on stability of ITO suspension were also investigated.The results show that the stability and dispersion mechanisms of the three dispersants are electrostatic and steric hindrance,and make ITO suspension keep RSH10% within 15 days under the conditions that the dispersant/ITO powder is 5%(mass ratio) and optimal ball milling dispersion time is 48 h.The sequence of effects of these three dispersants on the stability of ITO suspension is PVPβ-alaninetriammonium citrate,which is in agreement with the sequence of their acidity and alkalinity in the suspension.Among these three dispersants,PVP is the best one for the stability of ITO suspension.
Suspension
Dispersion stability
Alkalinity
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The dispersion behavior of ultrafine graphite in aqueous system was investigated by the sedimentation test. The dispersion effect of 12 kinds of dispersants were studied. By testing the changes of Zeta potential and the viscosity of suspensions with the addition of dispersants, the dispersion mechanism of dispersants was discussed by the calculation of the interaction energies between particles. The results show that traditional surfactants have poor performance on the stability of dispersion, but carboxymethylcellulose and polypropylene acid sodium are the efficient dispersants of graphite. The addition of dispersants can enlarge the absolute value of Zeta potential, increase the stability and decrease the viscosity of the dispersion. The optimum addition of dispersant is 500 mg/L and the suitable pH value is 8.510.5. The calculation results show that the dispersion of hydrophobic graphite does not conform to the DLVO theory. The hydrophobic interaction on the surface of particles controls the dispersion and coagulation of particles and the main effect of dispersants is to increase the electrostatic force and the interspace resistance.
DLVO theory
Zeta potential
Dispersion stability
Apparent viscosity
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Zeta potential
Suspension
Dispersion stability
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원자력발전소의 2차 계통수 중에 존재하는 철산화물(magnetite)은 열전달 튜브의 표면에 침착(fouling)되어 열전달 성능을 떨어뜨리거나 부식을 유발한다. 이와 같은 문제를 방지하기 위해, 원전 2차 계통수 중에 고분자 분산제(polymeric dispersant) 주입을 통해 철산화물의 분산 안정성 향상을 도모하는 연구를 수행하였다. 카르복실기(-COOH, carboxyl group)를 함유한 3종의 음 이온성 고분자(PAA, PMA, PAAMA)를 선정하였으며, 이들에 농도변화(1~1000 ppm)에 의한 마그네타이트 분산 특성을 평가하기 위해 침강시험, 투과율 측정, 입도 측정, 제타전위 측정을 수행하였다. 고분자 분산제는 수용액 중 철산화물 분산안정성에 큰 영향을 미쳤다. 분산제가 주입되면 분산 안정성이 향상되는 경향을 보였으나, 분산제 농도 증가에 따라 마그네타이트의 분산 안정성이 선형적으로 비례하여 증가하지 않았다. 이는 임계 분산제 농도 이상에서는 철산화물 사이의 응집(agglomeration)이 발생하기 때문인 것으로 사료된다. 분산안전성 향상 효과는 분산제-철산화물의 농도비(ppm, 분산제/마그네타이트)가 0.01~0.1 범위에서 현저하였다. 분산제 주입을 통한 철산화물 제거 효과를 최대화하기 위해서는 적용 환경 특성, 철산화물 농도, 분산제 농도 및 철산화물-분산제 농도비의 최적화가 필요한 것으로 판단된다. The iron oxide ($Fe_3O_4$ ) particles in the coolant of the secondary system of a nuclear power plant reduce the heat transfer performance or induce corrosion on the surface of the heat transfer tube. To prevent these problems, we conducted a study to improve the dispersion stability of iron oxide using polymeric dispersant injection in simulated secondary system water. The three kinds of anionic polymers containing carboxyl groups were selected. The dispersion characteristics of the iron oxide particles with the polymeric dispersants were evaluated by performing a settling test and measuring the transmission, the zeta potential, and the hydrodynamic particle size of the colloid solutions. Polymeric dispersants had a significant impact on the iron oxide dispersion stability in an aqueous solution. While the dispersant injection tended to improve the dispersion stability, the dispersion stability of iron oxide did not increase linearly with an increase in the dispersant concentration. This non-linearity is due to the agglomerations between the iron oxide particles above a critical dispersant concentration. The effect of the dispersant on the dispersion stability improvement was significant when the dispersant concentration ratio (ppm, dispersant/magnetite) was in the range of 0.1 to 0.01. This suggests that the optimization of dispersant concentration is required to maximize the iron oxide removal effect with the dispersant injection considering the applied environments, the iron oxide concentration and the concentration ratio of dispersant to iron oxide.
Dispersion stability
Zeta potential
Particle (ecology)
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The effect of various dispersion stabilization parameters on particle size, stability, and self-cleaning activity of titania aqueous dispersion was investigated with a focus on stability during preparation, storage, and introduction of fabric in the dispersion. Effect of parameters such as sonication, high-speed mixing, pH, and addition of ionic and nonionic dispersants was studied. The degree of surface charge on titania influences its stability and depends on the type of pH and dispersant. The stability of titania dispersion with the immersion of cotton, was also found to be a strong function of pH, dispersants and their combination. With the immersion of cotton in the dispersion ξ potential was >40 mV in the pH range of 1–3, and then gradually becomes close to zero in the pH range 4–7, then decreased further with the increase in pH. In the study of combined effect of pH and dispersants, influence of pH on ξ potential was independent in case of ionic dispersants and addition of nonionic dispersant has significant pH dependence. Self-cleaning activity (SCA) of titania-treated cotton fabric was quantitatively assessed by a standard method known as stain degradation assessment (SDA) method. SCA was highest at pH 2 followed by that at pH 10 and 12. In the presence of cationic dispersant, CTAB, ξ potential was >50 mV before and after cotton immersion and high SCA was obtained, however, in the presence of sodium salt of PAA, stable dispersion was obtained, but SCA reduced.
Dispersion stability
Sonication
Surface charge
Zeta potential
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수용액 중에서 poly (acrylic acid)(PAA)와 poly (ethylene oxide)(PEO)간의 수소결합을 통한 고분자 착체형성에 있어서 용매 및 외부조건의 변화가 미치는 영향을 모세관점도계 및 전위차계를 사용하여 조사하였다. 수용액의 pH가 낮을수록 PAA의 해리도의 감소로 인하여 착체형성이 더욱 유리하였으며, 물-알코올 혼합용매계에서는 알코올의 영향으로 착체형성의 극대점이 PAA/PEO=1 : 1에서 2 : 3으로 이동하였으며, 착체형성의 정도 또한 감소하였다. 그리고, 물에 요소 및 무기염의 첨가는 소수성상호작용 및 정전상호작용의 결과로 수소결합을 통한 착체형성에 방해요인이 되었음을 점도측정을 통한 고분자의 수력학적 크기의 변화를 통하여 확인하였다.
Acrylic acid
Poly ethylene
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Dispersant plays an important role in the manufacture and application processes of disperse dyes.The influence of different nonionic dispersants on the dispersion stability of C.I.Disperse Yellow 64 was investigated and the relationship between the molecular structures and properties of dispersant was discussed.The results showed that the stability of dispersion system has a lot to do with the hydrophilic-lipophhilic property and the combining situation of dispersant and dye particles.Appropriate hydrophilic-lipophhilic property and fast combination between hydrophobic part of dispersant and dye particles were helpful to improve the stability of dispersion system.Because the dosage of dispersant was low,the stability of dispersion system at high temperature mainly related to the cloud point of nonionic dispersant and its combination with dye particles.At the same time,excessive nonionic dispersant in the dispersion system could result in low stability at high temperature.
Dispersion stability
Disperse dye
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Aiming at defects such as small pits and scratches on the surface caused by the aggregation of alumina particles during the chemical mechanical polishing (CMP) process of the cemented carbide inserts, the effect of the dispersant types, pH and dispersant concentration on the dispersion stability of the alumina suspension is investigated. It is found that sodium dodecyl sulfate (SDS) is the best dispersant of the six different dispersants, and the suspension has good dispersion stability when the pH value is 11 and the SDS concentration is 3 wt%. Furthermore, based on the DLVO theory, SDS is verified to improve suspension stability at the micro-scale. Finally, the insert CMP experiments are carried out using the polishing slurry with SDS and without dispersant. CMP experiments show that using the polishing slurry with SDS to polish the insert can achieve a better material removal rate (MRR) and lower surface roughness.
Dispersion stability
Cemented carbide
Chemical Mechanical Planarization
Suspension
Sodium dodecyl sulfate
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