Block–random copolymer stabilisers for semi-batch emulsion polymerisation

Werner, Arthur; Sanders, Connor A.; Smeltzer, Sandra; George, Sean; Gernandt, Andreas; Reck, Bernd; Cunningham, Michael F.

doi:10.1039/d3py00085k

Cited by 1 publication

(11 citation statements)

References 37 publications

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“…It appears that the BRC aggregate properties, the conformation of the chains on the surface of PS, and the slow adsorption of chains to new interfaces may be responsible for the mechanistic differences observed in emulsion polymerizations stabilized by PS-b-P(S-r-AA). 28,29 This work extends our understanding of the behavior of PSb-P(S-r-AA) in aqueous environments. Investigating the nature of the aggregates as a function of continuous phase conditions is critical for understanding the nucleation and stabilization processes in emulsion polymerization.…”

Section: ■ Conclusionsupporting

confidence: 58%

“…In the context of emulsion polymerization stabilization, the nature of the aggregates and the stabilization of colloidal particles impact the emulsion polymerization process. Previously, our group has observed changes in the mechanism of emulsion polymerizations stabilized by BR1 with changes in pH and Φ . Decreasing the concentration of added NaCl of the emulsion polymerization from 100 to 0 mM, the stable latex particle surface area produced by each BR1 chain, a s , was enhanced by an order of magnitudethe chains became more efficient stabilizers.…”

Section: Resultsmentioning

confidence: 95%

“…Recently, we found that a reduction in the pH leads to significant changes in the emulsion polymerization process. 29 Specifically, as the initial pH (pH i ) decreases from 9.8 to 8.5, the final diameter of latex particles increases from 170 to 350 nm. However, at pH i = 7.9 and 7.4, the latex particle diameter decreases to 90 and 115 nm, respectively.…”

Section: ■ Introductionmentioning

confidence: 99%

“…These observations are in line with recent work with BR1 in stabilizing styrene emulsion polymerizations where a s values increase with pH near the pK a . 29 Moreover, it appears that the pH influence is far more substantial compared to Φ.…”

Section: ■ Introductionmentioning

confidence: 99%

“…As such, fewer coagulation events are expected at low pH as reported previously. 29 Conversely, at high pH conditions, the chains are spread out and compressed in the aggregates and therefore cannot spread out to stabilize new surface area as a latex particle grows. Moreover, it appears at all conditions that adsorption of BR1 chains to a new interface is slow, suggesting that new surface area is not stabilized by adsorption of new chains, leading to coagulation unless the adsorbed chains can spread out.…”

Section: ■ Introductionmentioning

confidence: 99%

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Amphiphilic Block Random Copolymers: Influence of pH and Ionic Strength on Aqueous Solution Properties

Sanders,

Werner,

Smeltzer

et al. 2024

Macromolecules

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Aqueous solution properties of polystyrene-b-poly-(styrene-r-acrylic acid), PS-b-P(S-r-AA), block−random copolymers (BRC) as a function of pH and ionic strength are reported using light scattering and surface tensiometry. Critical aggregation concentrations (CAC) are two orders of magnitude greater than similar PS-b-PAA block copolymers at pH >7.7; however, the CAC approaches that of block copolymers as the pH approaches the pK a of the BRC (pH = 7.0, pK a ∼6.3). Aggregation numbers (N agg ) between 5 and 26 are observed under alkaline conditions, about one to two orders of magnitude lower than those of PS-b-PAA block copolymers. Lowering the pH from 9.5 to 7.0 and increasing the ionic strength from 30 to 1000 mM reduced CAC and increased N agg due to a lower effective charge along the BRC chains. Analysis of the multichain aggregates using a core−corona spherical model showed that the PS-r-PAA blocks are compressed on the surface of the PS core due to the favorable mixing of the PS units. The BRCs are surface active above 0.1 g/L and slow to adsorb to interfaces. Results are related to previous work with emulsion polymerizations stabilized by BRC, suggesting that the structure of the aggregates and the slow adsorption kinetics play significant roles in the emulsion polymerization mechanism.

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Section: ■ Conclusionsupporting

confidence: 58%

Section: Resultsmentioning

confidence: 95%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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