Polyglycerol Surfmers and Surfactants for Direct and Inverse Miniemulsion

Colloid, interface, and foam properties of water-soluble polyglycerol esters solutions

HYPOTHESIS

Polyglycerol esters of fatty acids are generated via the esterification of a polydisperse mixture of polyglycerol with naturally derived fatty acids. The polymerization process of polyglycerol results in the production of various oligomers, ranging from di-, tri-, and higher-order forms, which contribute to the complexity of final products. The combination of complementary experimental techniques and adequate theoretical interpretations can reveal the wide variety of their physicochemical properties.

EXPERIMENTS

The colloid and interface properties of polyglyceryl mono-laurate, mono-stearate, mono-oleate, and a mixture of mono-caprylate and mono-caprate esters solutions were characterized by measurements of the electrolytic conductivity, static and dynamic surface tension, aggregate and micelle sizes and distributions, thin liquid film stability and stratification, and solubility in aqueous and in oil phases. The formation, stability, and bubble size distribution of foams generated from polyglycerol esters aqueous solutions were systematically investigated.

FINDINGS

The low concentrations of double-tail molecules and fatty acids in polyglycerol esters affect considerably their micellar, aggregation, and vesicle formations in aqueous solutions. The theoretical data interpretation of polyglycerol esters isotherms and thin liquid films data provide information on the adsorption energies, excluded areas per molecule, interaction parameters of molecules at interfaces, surface electrostatic potential, and the size of micelles. Polyglyceryl mono-oleate exhibits spontaneous emulsification properties. Short chain length polyglycerol esters have excellent foaming ability but relatively low foam stability. The optimal weight fractions of the short-chain polyglyceryl esters and polyglyceryl mono-stearate mixtures with respect to good foaminess and foam stability upon Ostwald ripening are obtained. The reported physicochemical characterization of the water-soluble polyglycerol esters could be of interest to increase the range of their applicability in practice.

Acetal-Based Functional Epoxide Monomers: Polymerizations and Applications

Protecting group chemistry is essential for various organic transformation and polymerization processes. In particular, conventional anionic ring-opening polymerization (AROP) often requires proper protecting group chemistry because it is typically incompatible with most functional groups due to the highly basic and nucleophilic conditions. In this context, many functional epoxide monomers with proper protecting groups are developed, including the acetal group as a representative example. Since the early introduction of ethoxyethyl glycidyl ether, there is significant development of acetal-based monomers in the polyethers. These monomers are now utilized not only as protecting groups for hydroxyl groups under AROP conditions but also as pH-responsive moieties for biomedical applications, further expanding their utility in the use of functionalized polyethers. Recent progress in this field is outlined from their synthesis, polymerization, and biomedical applications.

Evidence of protein coronas around soft nanoparticles regardless of the chemical nature of the outer surface: structural features and biological consequences

The formation of biomolecular coronas around nanoparticles as soon as they come in contact with biological media is nowadays well accepted. The self-developed biological outer surfaces can affect the targeting capability of the colloidal carriers as well as their cytotoxicity and cellular uptake behavior. In this framework, we explored the structural features and biological consequences of protein coronas around block copolymer assemblies consisting of a common pH-responsive core made by poly[2-(diisopropylamino) ethyl methacrylate] (PDPA) and hydrophilic shells of different chemical natures: zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) or highly hydrophilic poly(ethylene oxide) (PEO) and poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA). We demonstrated the presence of ∼50 nm protein coronas around the nanoparticles regardless of the chemical nature of the polymeric shells. The thickness is understood as the sum of the soft and hard layers and it is the actual interface seen by the cells. Although the soft corona composition is difficult to determine because the proteins are loosely bound to the outer surface of the assemblies, the tightly bound proteins (hard corona) could be identified and quantified. The compositional analysis of the hard corona demonstrated that human serum albumin (HSA), immunoglobulin G (IgG) and fibrinogen are the main components of the protein coronas, and serotransferrin is present particularly in the protein corona of the zwitterionic-stabilized assemblies. The protein coronas substantially reduce the cellular uptake of the colloidal particles due to their increased size and the presence of HSA which is known to reduce nanoparticle-cell adhesion. On the other hand, their existence also reduces the levels of cytotoxicity of the polymeric assemblies, highlighting that protein coronas should not be always understood as artifacts that need to be eliminated due to their positive outputs.

Synthesis, Characterization, Self-Assembly, and Irritation Studies of Polyglyceryl-10 Caprylates

1,4-dioxane should be less than or equal to 10 ppm in finished cosmetic products according to the recommendation of the Scientific Committee on Consumer Safety, but it is often generated as a by-product during the manufacturing process of poly(ethylene glycol) (PEG)-based derivatives. In order to avoid the possible risk caused by 1,4-dioxane, it might be a good choice for preparing cosmetic ingredients by using polyglycerin (PG) instead of PEG as a hydrophilic segment. In the present study, polyglyceryl-10 caprylates were synthesized by the esterification reaction between polyglycerin-10 and caprylic acid. FTIR and 1H NMR were utilized to confirm the chemical structures of the obtained polyglyceryl-10 caprylates. Light transmittance was availed to investigate the water solubility of polyglyceryl-10 caprylates. The self-assembly behavior, size, and size distribution of polyglyceryl-10 caprylates were investigated by dynamic light scattering. The makeup cleansing effect was also evaluated by in vitro and in vivo methods. Irritation was evaluated by hen's egg test-chorioallantoic membrane assay (HET-CAM). Results showed that polyglyceryl-10 monocaprylate could self-assemble into nanoparticles in the water at the concentration range of 2.5-10 wt% with a transparent appearance. The diameter of formed nanoparticles was around 100 nm with a narrow particle size distribution around 0.1 at the concentration of 2.5 wt% or 5 wt%. Polyglyceryl-10 monocaprylate exhibited good removal effect against makeup and excellent removal efficacy against pen eyeliner. The irritation of polyglyceryl-10 monocaprylate evaluated by HET-CAM at the concentration of 4 wt% was moderate irritant (irritation score = 8.4), which was lower than that of PEG-6 caprylic/capric glycerides (severe irritant, irritation score = 14.1). Therefore, polyglyceryl-10 monocaprylate might be a promising cosmetic ingredient for transparent makeup removing water.

Surface-Functionalized Polystyrene Latexes Using Itaconate-Based Surfmers

Itaconic acid was readily transformed to a series of amphiphilic diesters via stepwise esterification of itaconic anhydride; the diesters carry one alkyl (cetyl or octyl) group and either a PEG, glyceryl, or dopamine segment. These diesters were used as surfmers for the preparation of polystyrene (PS) emulsions, with the expectation that the surface of the emulsion particles would carry PEG, glyceryl or dopamine units. NMR spectroscopic studies revealed that the surfmers were covalently incorporated into the polystyrene chains; furthermore, NMR tube polymerization experiments also confirmed that when the PEG surfmer was used, the PEG segments are indeed present on the surface of the emulsion particles. The size of the PEGlyated PS emulsions was readily varied from 35 to 140 nm by changing the mole fraction of surfmer used. In the case of the glyceryl and dopamine carrying surfmers, an octyl unit was used as the hydrophobic segment to ensure appropriate hydrophobic-hydrophilic balance; it was noticed that significantly larger mole fractions of the surfmers were required (15-20 mol %) to generate stable emulsions with particle sizes of about 150 nm. The PS emulsions carrying dopamine units on the surface were found to adhere to glass surfaces; thus suggesting that such "sticky" emulsion particles could be used to functionalize different types of surfaces. Finally, itaconate diesters bearing cetyl and perfluorooctyl segments were also prepared and shown to copolymerize with styrene to generate fluoroalkyl-enriched PS copolymers; these were used to generate hydrophobic coatings, with water contact angles of over 120°. Thus, itaconate-based surfmers are readily accessible alternatives for the preparation of emulsions with tailored size and surface functionality.

Active Ester Containing Surfmer for One-Stage Polymer Nanoparticle Surface Functionalization in Mini-Emulsion Polymerization

Functional surface active monomers (surfmers) are molecules that combine the functionalities of surface activity, polymerizability, and reactive groups. This study presents an improved pathway for the synthesis of the active ester containing surfmer p-(11-acrylamido)undecanoyloxyphenyl dimethylsulfonium methyl sulfate (AUPDS). Further, the preparation of poly(methyl methacrylate) and polystyrene nanoparticles (NPs) by mini-emulsion polymerization using AUPDS is investigated, leading to NPs with active ester groups on their surface. By systematically varying reaction parameters and reagent concentrations, it was found that AUPDS feed concentrations between 2⁻4 mol% yielded narrowly distributed and stable spherical particles with average sizes between 83 and 134 nm for non-cross-linked NPs, and up to 163 nm for cross-linked NPs. By basic hydrolysis of the active ester groups in aqueous dispersion, the positive ζ-potential (ZP) was converted into a negative ZP and charge quantities determined by polyelectrolyte titrations before and after hydrolysis were in the same range, indicating that the active ester groups were indeed accessible in aqueous suspension. Increasing cross-linker amounts over 10 mol% also led to a decrease of ZP of NPs, probably due to internalization of the AUPDS during polymerization. In conclusion, by using optimized reaction conditions, it is possible to prepare active ester functionalized NPs in one stage using AUPDS as a surfmer in mini-emulsion polymerization.