Effect of Polymer Surfactant on Emulsion Polymerization of Styrene Under Ultrasonic Irradiation

Effect of Polymer Surfactant on Emulsion Polymerization of Styrene Under Ultrasonic Irradiation ZHANG Jing-Zhi, CAO Ya* (State Key Laboratory of Polymer Materials Engineering, Institute of Polymer Research, Sichuan University, Chengdu 610065, China) The agent is produced, but sodium dodecyl sulfate is broken under ultrasonic irradiation, and free radicals are generated. By studying the reaction kinetics, it is found that the mechanism of emulsion polymerization under ultrasound irradiation is different from that of conventional emulsion polymerization. The polymerization process has only two charges. Segments, ie, acceleration and deceleration periods, there is no constant speed period. Adding CM C-A9 polymer surfactant can achieve higher monomer conversion in a shorter time and lower ultrasonic power.

Conventional emulsion polymerization is one of the earliest methods for preparing polymeric microspheres of a certain size and distribution, and the resulting product is a colloidally stable latex dispersed by an emulsifier. Nowadays, nanotechnology has penetrated into various fields. It is of great significance to prepare polymer microspheres with narrow size distribution. In recent years, ultrasonic irradiation technology has introduced emulsion polymerization. Due to the unique cavitation effect of ultrasonic irradiation, It is possible to initiate the reaction and prepare nano-sized polymer microspheres without the addition of a chemical initiator. This technique has attracted widespread attention. It is known that emulsifiers have a great influence on the emulsion polymerization reaction. Since the general emulsifiers are low-molecular compounds, the lipophilic end is connected to the surface of the polymer micelle by physical adsorption, so that the latex does not tolerate electrolytes and is easy to flocculate, while the amphiphilic polymer, ie, the polymer surfactant, can just To overcome the above drawbacks, ultrasound irradiation was introduced into the emulsion polymerization of styrene, and a novel carboxymethyl cellulose-based block copolymer with hydrophilic and oleophilic long-chain branches was added. It was not only the stability of latex. Agents, but also have emulsification and other functions, have a greater impact on the reaction process and the size of the latex, this article focuses on the impact of this polymer surfactant on the polymerization kinetics.

1 Experimental Section 1.1 Styrene (St): Chemically pure reagent, vacuum distillation before use; sodium dodecyl sulfate (SDS): analytically pure, used directly; carboxymethyl cellulose (CMC): Guangzhou Huaxian South Show Chemical Co., Ltd. product, carboxymethyl degree of substitution of 1.02, purity> 95%; carboxymethyl cellulose and dodecyl alcohol polyoxyethylene acrylate copolymer (CMC-A9, polyoxyethylene chain length of 9) : Self-manufactured in the laboratory, with a molecular weight of 1.69 (105, dodecyl alcohol polyoxyethylene acrylate block content of 10%, a high surface activity (0.5% aqueous solution with a surface tension of 30.4mN/m) Block copolymer 1.2 Polymerization 1500 Ultrasonic Generator (USA), maximum power 1500W, adjustable output power, 600W output power in the experiment, titanium alloy probe.

A certain proportion of St SDS aqueous solution and CMC-A9 aqueous solution were added to a self-designed ultrasonic reactor, N2 was introduced, and the cooling was conducted. A constant temperature (25 t2)*C. The ultrasonic wave was turned on for reaction. After irradiating for a while, the reaction was completed. Fund project: Zhang Jingzhi, funded by the Yangtze River Scholar Young Backbone Teachers Fund of the Ministry of Education: Impact of Polymer Surfactants on Emulsion Polymerization of Styrene under Ultrasonic Irradiation Fig.1: Without SDS, Volume Percentage of Styrene Monomer (h) 1 (%, conversion curve at different concentrations of CMC-A9, the conversion rate of monomer is very low. It is generally considered that under high-frequency irradiation, the polymer broken chain generates free radical initiation reaction, but by Fig. 1 According to the analysis, the efficiency of the free radical initiation reaction produced by CMC-A9 is not high, and the analysis of the infrared spectrum shows that the spectrum of the polymer not added with CMC-A9 is basically the same, and is a spectrum of polystyrene and does not appear. The characteristic peak of CMC-A9 is C=O, so CMC-A9 is not involved in the reaction.Fig.2 is the conversion time curve at different SDS concentrations, the volume percentage of styrene monomer is 10%, and the concentration of CMC-A9 is 0.7g. /L experimental results show that when When the SDS is not added to the system, the polymerization reaction hardly proceeds. With the addition of the SDS concentration, the conversion rate rapidly increases. SDS plays an important role in the initiation of emulsion polymerization by ultrasonic irradiation, and it is mainly responsible for the production of free radicals or the promotion of free radicals. Factors Stoffer et al./dt)=dT/dt:R--reaction rate;--radical concentration;--initial monomer concentration; T-monomer conversion rate; dT/dt may be calculated from the conversion time curve derivation , PS powder and KBr grinding tablets, resolution 2cm \ scanning times 20 times.

Polymer Materials Science and Engineering CMC only has the role of colloids. Classical cavitation theory shows that pressure; Re a cavitation bubble radius; e - liquid surface tension; ph - hydrostatic pressure. Because CMC-A9 can reduce the surface tension of the liquid and thus reduce the outside, making it easier to form cavitation bubbles, the cavitation effect is enhanced.

Fig. 4 shows that the reaction rate curve at different conversion rates is different from that of ordinary emulsion polymerization, and the polymerization process only has two stages. This shows that the nucleation method under ultrasonic irradiation is different from that of ordinary emulsion polymerization. This is due to the fact that under strong shearing and stirring by ultrasonic waves, the monomers are dispersed into small droplets. The added surfactant, especially CMC-A9, stabilizes the small droplets and swells monomer droplets and monomers. There is a dynamic equilibrium in the micelles, the number of monomeric droplets is sufficient to be in and out of micelles, and also occurs in monomeric droplets. On the other hand, due to the unique effect of ultrasonic irradiation, free radicals are mainly generated by the breakage of SDS, and free radicals have been generated during the reaction. Therefore, the initial reaction rate is fast and the monomer consumption is too high. After a certain period of time, the reaction rate begins to decrease (>2.8%). 5 shows that the 303 concentration is 30/2. The effect of different concentrations of CMC-A9 on the conversion rate is shown in the figure. It can be seen that when there is no CMC-A9 in the system, the conversion rate of the monomer is lower, and with the increase of the concentration of CMC-A9, the monomer conversion rate increases, and when the concentration of CMC-A9 is 1.4 g/L, the monomer conversion rate is within 60 minutes. About 85% is achieved. Therefore, CMC-A9 has the effect of increasing the conversion of monomers in a shorter time. Fig.7 is added with 0.7g/LCMC-A91.4g/LCMC-A9 at different ultrasonic output powers. The conversion rate The number of beam bundles In addition to the nucleation of latex particles in addition to the gel curve, we can see from the two graphs that 0.7g/LCMC-A9, Zhang Jingzhi et al.: Polymeric Surfactants for Ultrasonic Irradiation of Styrene Emulsion The influence of the polymerization on the monomer conversion was decreased with the decrease of the ultrasonic power and the concentration of CMC-A9 was 1.4 g/L, and a higher monomer conversion rate was also achieved at a lower ultrasonic power. The increase of CMC-A9 concentration, the less obvious the effect of ultrasonic power on the conversion rate-time curve, namely the conversion rate Do not decrease with power reduction Therefore, in the ultrasonic irradiation of styrene emulsion polymerization, the addition of the high-molecular surfactant CMC-A9 can achieve higher styrene monomer conversion in a shorter time and lower ultrasonic power.