Particle Size and Zeta Potential Analysis of Copolymer Latex


Polystyrene and butadiene can form nanocopolymer latex spheres through the process of emulsion polymerization. These spheres have many industrial applications including cement, paper and other areas of industry.

The surface of the latex, depending on the composition, can take on negative or positive charges which maintain the stability of the latex system. It is therefore essential to measure the zeta potential in order to evaluate the charges, which ultimately reveal the stability of the sample.

. Image credit: Bettersize Instruments Ltd.

the BeNano 90 Zeta (Bettersize Instruments Ltd.) was used in this process to take measurements of sizes and zeta potentials of polystyrene-butadiene copolymers that are dispersed in aqueous environments that derive from the same source but diverge in manufacturing processes.

Instrumentation

A semiconductor laser beam with a wavelength of 671 nm and a power of 50 mW illuminates the sample In the BeNano 90 Zeta, an iber-coupled avalanche photodiode (APD) detector, which is used to collect scattered light signals from 12° for zeta potential measurement and 90° for size measurement.

Experience

In order to obtain size and zeta potential measurements, two copolymer latices were diluted 1000 times in pure water.

In order to study the repeatability of the results and to obtain the standard deviation of the result, each sample was measured at least three times.

Results and discussion

In this experiment, the sizes and zeta potentials of two latex samples were obtained. The size distribution curves of the two samples are shown in Figure 1. As shown in Figure 1, it appears that both samples are at the nanoscale, with only narrow peaks and no large aggregates.

The phase diagrams and trend diagrams of the zeta potential of SLE measurement are displayed in Figure 2 and Figure 3. The frequency shifts of the scattered light due to electrophoresis are represented by the slopes of the phase plots. The clear slopes of the phase plots display strong signal-to-noise ratios of the measurements, as these numbers show.

Figure 1. Particle size distribution curves of sample 1# and sample 2# copolymers.  Image credit: Bettersize Instruments Ltd.

Figure 1. Size distribution curves of sample 1# and sample 2# copolymers. Image credit: Bettersize Instruments Ltd.

Figure 2. Phase diagram and trend diagram of the zeta potential of sample 1#.  Image credit: Bettersize Instruments Ltd.

Picture 2. The phase diagram and trend diagram of sample 1# zeta potential. Image credit: Bettersize Instruments Ltd.

Figure 3. Phase diagram and trend diagram of the zeta potential of sample 2#.  Image credit: Bettersize Instruments Ltd.

Picture 3. The phase diagram and trend diagram of sample 2# zeta potential. Image credit: Bettersize Instruments Ltd.

Table 1 shows several measurement results of two samples, indicating that the difference in size is small. The samples are tightly distributed in size, which is evidenced by the fact that the PDI of both samples was well below 0.05.

Concerning the zeta potentials, the signs are negative and the absolute values ​​are greater than 30 mV. These figures indicate that, in order to maintain the stability of the latex system, a large number of negative charges are carried by the surfaces of the particles to generate strong electrostatic repulsion.

Table 1. Measurement results of two latex samples. Source: Bettersize Instruments Ltd.

To taste Z-average(nm) PD.I Zeta potential (mV)
1# 155.76 0.010 -52.76±1.31
2# 170.31 0.002 -58.90±1.68

conclusion

The size and zeta potential of the two polystyrene-butadiene copolymer latices have been successfully characterized through the use of the BeNano 90 Zeta. From the result, it is clear that the two copolymers are monodisperse in size and are less likely to form aggregates due to the high zeta potentials.

This information has been extracted, reviewed and adapted from materials provided by Bettersize Instruments Ltd.

For more information on this source, please visit Bettersize Instruments Ltd.

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