Polyethylene glycol (PEG) is formed by the stepwise addition polymerization of ethylene oxide and water or ethylene glycol. It has good water solubility and good compatibility with many organic components. Because of its excellent lubricity, moisture retention, and dispersibility, it is widely used in cosmetics, pharmaceuticals, chemical fiber, rubber, plastics, papermaking, paint, electroplating, pesticides, metal processing, and food processing industries. Polypropylene glycol (PPG) is colorless to pale yellow viscous liquid. Lower molecular weight polymers are soluble in water, and higher molecular weight polymers are soluble in oils, many hydrocarbons, and aliphatic alcohols, ketones, and esters. PPG is a solvent for vegetable oils, resins and paraffin, and is also used to prepare alkyd resins, emulsifiers, demulsifiers, lubricants and plasticizers. It is usually obtained by condensation of propylene oxide and propylene glycol in the presence of high pressure or acid catalyst. Polyethylene glycol-polypropylene glycol (PEG-PPG) copolymer is a polymer formed by the polymerization of two monomers, PEG and PPG, and can be used as a detergent, emulsifier, dispersant, solubilizer, lubricant and defoamer.
Figure 1. The structural formula of PEG/PPG copolymer
- Chemical field: SiO2 hollow spheres can be prepared by using triblock copolymer polyethylene glycol-polypropylene glycol-polyethylene glycol (PEG-PPG-PEG) as a template. Take PEG-PPG-PEG/deionized water/benzyl alcohol/absolute ethanol to participate in the reaction at a certain ratio, with Na2SiO3 as the precursor of SiO2, adjust the pH value with NaOH solution, and calcinate to remove the template at 550℃-4h. By changing the ratio of the reactants and the reaction time, it is possible to finally obtain regular mesoporous SiO2 hollow microspheres with a shell thickness of about 80 nm and an average inner diameter of 1000 nm.
Figure 2. SiO2 hollow sphere prepared with triblock copolymer polyethylene glycol-polypropylene glycol-polyethylene glycol (PEG-PPG-PEG) as template
- Industrial field: Polypeptide is a kind of biomaterial with good biocompatibility and biodegradability. Polypeptide membrane can be used as artificial skin, but the polypeptide membrane is relatively rigid and lacks hydrophilicity, which limits its application to a certain extent. PPG has good biocompatibility and biodegradability, is relatively soft and has good compatibility with PEG. Introduce the PPG segment into the polypeptide segment and PEG segment to form the polypeptide-polypropylene glycol block copolymer and PEG-PPG block copolymer, and then mix the two copolymers to form the blend with better compatibility can be used to prepare modified polypeptide membrane. The membrane can greatly improve the hydrophilicity and flexibility of the polypeptide membrane.
- Medical field: PEG-PPG can be used as the polymer molecular chain in polyrotaxane, and polyrotaxane can be widely used as a carrier for biological macromolecule drugs. For example, the formation of polyelectrolyte complex particles by cationic polyrotaxane and genes can avoid the degradation of genes by nucleases, thereby safely delivering genes into cells. It can effectively improve the transfection rate while greatly reducing cytotoxicity, indicating the great potential of polyrotaxane as a non-viral gene-drug carrier. In addition, polyrotaxane can also be combined with many drugs such as anticancer drugs and biomacromolecule drugs for slow release and targeting.
Figure 3. Structure of chain polyrotaxane
- Nakahata, Masaki. (2016) "Self-Healing Materials Formed by Cross-Linked Polyrotaxanes with Reversible Bonds." Chem. 1:766-775.
- Wu J, Mather P.T. (2009) "POSS polymers: Physical properties and biomaterials applications." Polym. Rev. 49:25–63.