Synthesis, Characterization, and Viscoelastic Properties of High Molecular Weight Hyperbranched Polyglycerols

Abstract

Very high molecular weight (M n up to 700 000) and narrowly polydispersed (PDI = 1.1−1.4) hyperbranched polyglycerols (HPG) were synthesized by ring-opening multibranching polymerization of glycidol using dioxane as an emulsifying agent. Broader molecular weight distributions with low molecular weight fractions were obtained when diglyme was used as the emulsifying agent. But the low molecular weight fractions could be removed by dialysis. Isolated yields in both the cases were 70−90%. The different result in the case of dioxane may be due to faster cation exchange which leads to low polydispersites. HPGs of various molecular weights were characterized by a GPC system coupled with a multiangle laser light scattering detector and a triple detector array. The intrinsic viscosities were low for these polymers and did not increase with molecular weight. The dimensions of these polymers (R g, R h, R η) and their dependence on molecular weights are described. The hydrodynamic radii were very small with dimensions similar to those of dendrimers. Our results show that these polymers are very compact and have spherical conformations in water with no indications of aggregate formation. The melt viscoelastic properties were also studied. Despite their self-similar structures, depending on the type of solvent used to synthesize them (diglyme vs dioxane), topologically restricted configurations are produced that result in completely different entanglement dynamics.

Preparation and properties of multi-branched poly(D-lactide) derived from polyglycidol and its stereocomplex blends

“…Detailed information on chemical structure of PG can be derived from 13 C NMR Inverse Gated spectra, in which complicated patterns of perfect dentritic (D), linear (L), and terminal (T) units can be identified. The assignments have been applied to 13 C NMR (b), and 13 C NMR DEPT (c) spectra of PG synthesized from tin catalyst the spectra of PG synthesized from anionic polymerization [41][42][43][44]. Similar spectral characteristics are observed in this study, in which a tin catalyst is employed, as shown in a 13 C NMR and a distortionless enhancement by polarization transfer (DEPT) spectra in Figure 1b and 1c, respectively.…”

“…The relative intensity of the high-molecular weight fraction increases with the decrease in the catalyst contents. Although the polydispersity value (~3.4) is significantly high, compared to that obtained from anionic polymerization [41][42][43][44], this synthesis route is considered as an alternative approach when structural perfection may not be a strict requirement for most applications.…”

Hyperbranched Polyglycerol is an Efficacious and Biocompatible Novel Osmotic Agent in a Rodent Model of Peritoneal Dialysis

“…Hyperbranched polyglycerol can be precisely synthesized over a wide range of molecular weights and is chemically stable as a narrow distributed polymer in aqueous solution (11)(12)(13). It is highly hydrophilic and water-soluble (>400 mg/mL), with a very low intrinsic viscosity (4 -7 mL g -1 ), and therefore large amounts of the polymer can easily be dissolved in water (13,14). It also has multiple hydroxyl groups per molecule of polymer and exists at physiologic pH in aqueous solution (14).…”

Hyperbranched aliphatic polyether polyols

“…72 In a very interesting work in this area, Brooks and coworkers added dioxane as an emulsifier in the established SMA procedure, obtaining extremely high molecular weight hbPG (M n up to 700 kg mol À1 ). 73 These materials exhibit the highest molecular weights obtained for synthetic hyperbranched polymers reported to date. To facilitate the synthesis of hbPG for industrial processing, microreactor technology 74 can be used to obtain polymers with molecular weights up to 1500 g mol À1 .…”