Polyethylene glycol is a high molecular polymer with the chemical formula HO(CH2CH2O)nH. It is non-irritating, has a slightly bitter taste, has good water solubility, and has good compatibility with many organic components. It has excellent lubricity, moisture retention, dispersion and adhesion, and can be used as an antistatic agent and softener in cosmetics, pharmaceuticals, chemical fibers, rubber, plastics, papermaking, paints, electroplating, pesticides, etc. And it is also widely used in metal processing and food processing industries.
Polyethylene glycol and polyethylene glycol fatty acid esters are widely used in the cosmetics and pharmaceutical industries. Because polyethylene glycol has many excellent properties: water solubility, non-volatility, physiological inertness, mildness, lubricity, and moisturizing, softness, and pleasant after-use feeling of the skin. Polyethylene glycol with low relative molecular weight (Mr<2000) is suitable for use as a wetting agent and consistency regulator for creams, lotions, toothpastes, shaving creams, etc. Polyethylene glycol with high relative molecular weight (Mr>2000) is suitable for lipstick, soap, shaving soap, foundation and beauty cosmetics, etc. In cleaning agents, polyethylene glycol is also used as a suspending agent and thickening agent. In the pharmaceutical industry, it is used as a base for ointments, emulsions, ointments, lotions and suppositories.
Polyethylene glycol is widely used in a variety of pharmaceutical preparations, such as injectables, topical preparations, ophthalmic preparations, oral and rectal preparations. Solid grade polyethylene glycol can be added to liquid polyethylene glycol to adjust the viscosity and used for topical ointments; polyethylene glycol can be used in combination with other emulsifiers to increase the stability of the emulsion. In addition, polyethylene glycol is also used as a film coating agent, tablet lubricant, controlled release material, etc.
Phase separation is a ubiquitous phase transition process in nature: that is, each component in a homogeneous mixture spontaneously separates the system into two different regions driven by factors such as activity, viscoelasticity, and temperature. Phase separation occurs in common polymer blends, polymer solutions and colloidal nanoparticle suspensions. Therefore, a deep understanding of the phase separation process involves how to outline an ordered multi-scale self-assembly mechanism from a disordered system.
Some researchers have used rigid cellulose nanocrystal particles and flexible dextran-polyethylene glycol (PEG) binary polymers as model units, and a series of heterogeneous multiphase separation systems were constructed in an all-aqueous system including the liquid-liquid phase separation (LLPS) process of the polymer solution and the liquid crystal phase separation (LCPS) process of the cellulose nanocrystal particles. In the above multi-component polymer-cellulose nanocrystal mixture, the researchers controlled the phase separation behavior of the mixture by adjusting the trade-off between thermodynamics and kinetics in the LLPS and LCPS processes. Cellulose nanocrystals exhibit chiral self-assembly effects within separated aqueous polymer phases or between interfaces. In addition, they further constructed a temperature-concentration dual-response multi-phase separation system using the cellulose nanocrystal-Dextran-PEG ternary system, and obtained the LLPS-LCPS coupled phase transition process, that is, the mixture is uniform and stable at high temperatures. However, phase separation occurs when cooled to room temperature, demonstrating the thermotropic phase behavior in the lyotropic cholesteric liquid crystal matrix.
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Reference
- Thermodynamically controlled multiphase separation of heterogeneous liquid crystal colloids
Nat. Commun., 2023, 14, 5277
