and a large amount of functional groups with a comparably simple synthesis. The hyperbranched structure of a polymer is characterized by its degree of branching (DB), which can be calculated from the fraction of dendritic (D) and linear (L) units (Equation (1)). [1] = +Control of the branching density of hyperbranched polymers is important both with respect to key properties, such as viscosity, but also with respect to end group functionality. Fundamental work in understanding and quantifying the branching density of hyperbranched polymers was carried out for the AB m -polycondensation approach [1,2] as well as for the self-condensing vinyl polymerization. [3] A review article from 2012 by Higashihara et al. [4] focused on the methodologies to control the DB and summarized recent advances in the synthesis of hyperbranched polymers with a DB of 100% and values between 0% and 100%, mainly by condensation or addition reactions. These methods are based on a concept, in which the rate constants k 1 and k 2 for reaction of the two B-groups of an AB 2 monomer are different. [2] In a theoretical work, it was shown that copolymerizing branching AB m -type monomers with linear AB monomers represents a key strategy to control the degree of branching of hyperbranched polymers. [5] For hyperbranched polyglycerol (hbPG) this translates to the copolymerization of the latent AB 2 monomer glycidol with other epoxides as linear AB comonomers. This has been demonstrated for copolymers of glycidol with ethylene oxide and propylene oxide, leading to hyperbranched materials with glycerol branching points between linear oligo(ethylene glycol) or oligo(propylene glycol) segments. [6,7] In these cases, the DB could be varied between 0.07 and 0.59 with comonomer contents up to 97%. In a recent study, hyperbranched poly(ethylene glycol)-co-(glycerol) copolymers (hbPEGs) have been presented in a broad molecular
PolyglycerolsIn an oxyanionic polymerization, glycidol as a latent AB 2 monomer is copolymerized with the protected linear AB glycidyl ether monomer EEGE (ethoxy ethyl glycidyl ether) to generate hyperbranched polyglycerols with an adjustable degree of branching (DB) after deprotection. The DB for the random copolymers is controlled by the comonomer content (10-92% EEGE).