Poly(ethylene glycol) (PEG) and its derivatives have found a tremendous variety of applications in food production, cosmetics, and pharmaceutics due to its biocompatibility, chemical inertness and excellent solubility in both organic and aqueous media. Still, the high degree of crystallization and a maximum of two end groups in linear PEG are limiting its potential for further chemical modification and, for example, the loading capacity when used as soluble support for organic synthesis. To overcome these problems, the synthesis of hyperbranched poly(ethylene glycol) (hbPEG) in one step was realized by random copolymerization of ethylene oxide and glycidol.1
Figure 1: Schematic representation of the synthesis strategy for hbPEG.
Poly(propylene glycol) (PPG) is commercially used as a flexible, hydrophobic compound for surfactants and polyurethanes. Random copolymerization of propylene oxide with glycidol as a branching unit results in hyperbranched poly(propylene glycol) (hbPPG), a backbone-thermoresponsive polyether polyol. By varying the comonomer ratio, the number of hydroxyl groups and the critical solution temperature in water can be adjusted.2
Figure 2: Schematic representation of the synthesis strategy for hbPPG and its thermoresponsive behavior.
HbPEG and hbPPG combine the remarkable features of their linear analogues with the unique properties of a hyperbranched polymer having an amorphous structure, low intrinsic viscosities and multiple hydroxyl groups accessible for further functionalization. Hyperbranched poly(alkylene glycol)s themselves or used as building blocks for other structures open the path to new materials with many possible applications.3, 4, 5
|||"Hyperbranched PEG by random copolymerization of ethylene oxide and glycidol" D. Wilms, M. Schömer, F. Wurm, M. I. Hermanns, C. J. Kirkpatrick, H. Frey, Macromol. Rapid Commun. 2010, 31, 1811–1815. DOI: 10.1002/marc.201000329.|
|||"Hyperbranched Poly(propylene oxide): A Multifunctional Backbone-Thermoresponsive Polyether Polyol Copolymer" M. Schömer, J. Seiwert, H. Frey, ACS Macro Lett. 2012, 1, 888–891. DOI: 10.1021/mz300256y.|
|||"Correlations between Ion Conductivity and Polymer Dynamics in Hyperbranched Poly(ethylene oxide) Electrolytes for Lithium-Ion Batteries" S.-I. Lee, M. Schömer, H. Peng, K. A. Page, D. Wilms, H. Frey, C. L. Soles, D. Y. Yoon, Chem. Mater. 2011, 23, 2685–2688. DOI: 10.1021/cm103696g.|
|||"Organobase-Catalyzed Synthesis of Multiarm Star Polylactide With Hyperbranched Poly(ethylene glycol) as the Core" M. Schömer, H. Frey, Macromol. Chem. Phys. 2011, 212, 2478–2486. DOI: 10.1002/macp.201100386.|
|||"Controlled synthesis of multi-arm star polyether-polycarbonate polyols based on propylene oxide and CO2" J. Hilf, P. Schulze, J. Seiwert, H. Frey, Macromol. Rapid Commun. 2014, 35, 198–203. DOI: 10.1002/marc.201300663.|