PEG (Polyethylene glycol) has a wide range of applications, including but not limited to drug carriers, cosmetic ingredients, lubricants, dispersants, solubilizers, etc. Its versatility is due to the molecular structure and physicochemical properties of PEG, which can adapt to different application requirements.
PEG has good water solubility and can form a transparent solution in water, which makes PEG solvent widely used in pharmaceutical, cosmetic and personal care products. In addition, PEG can also be dissolved in many commonly used polar organic solvents, such as acetone, alcohol and chlorinated agents. The application of PEG in the biomedical field has proved its good biocompatibility and non-toxicity. It shows low toxicity and immunogenicity both in vivo and in vitro, so it is widely used in medical products such as drug delivery systems and surgical sutures. PEG has good chemical stability and is not easily oxidized or decomposed, which enables it to maintain stable physical and chemical properties under various environments.
Phase separation is a phase transition process that is commonly found in nature: that is, the components in a homogeneous mixture spontaneously separate the system into two different regions driven by factors such as activity, viscoelasticity, and temperature. Phase separation is a long-standing topic that essentially refers to the emergence of order from disorder in heterogeneous systems. It can be triggered by different stimuli and occurs in a variety of natural and synthetic transitions, including purification, compartmentalization, and material exchange. In order to minimize free energy, certain colloids can separate into two coexisting phases to achieve equilibrium. Specifically, dispersions of anisotropic particles undergo phase separation above a critical concentration, known as liquid crystal phase separation (LCPS), which has great potential and a wide range of applications in modern materials science. In another area, liquid-liquid phase separation (LLPS) in homogeneous macromolecular solutions is a prominent phenomenon in biological systems because it plays a leading role in enabling cellular functions and creating delicate structures in organisms.
Common polymer blends, polymer solutions, and colloidal nanoparticle suspensions all undergo phase separation, so a deep understanding of the phase separation process involves how to outline the ordered multiscale self-assembly mechanism from disordered systems. Some people have constructed a series of heterogeneous multiphase separation systems in an all-aqueous system by using rigid cellulose nanocrystal particles and flexible dextran-polyethylene glycol (PEG) binary polymers as model units, including the liquid-liquid phase separation (LLPS) of polymer solutions and the liquid crystal phase separation (LCPS) of cellulose nanocrystal particles.
In the above multi-component polymer-cellulose nanocrystal mixture, the authors controlled the phase separation behavior of the mixture by adjusting the trade-off between thermodynamics and kinetics in the LLPS and LCPS processes, so that the cellulose nanocrystals exhibited a chiral self-assembly effect within the separated aqueous polymer phase or between interfaces. In addition, they used the cellulose nanocrystal-Dextran-PEG ternary system to further construct a "temperature-concentration dual response" multiphase separation system and obtained the LLPS-LCPS coupled phase transition process, that is, the mixture is uniform and stable at high temperature, but phase separation occurs when cooled to room temperature, showing thermotropic phase behavior in the lyotropic cholesteric liquid crystal matrix.
