Hyperbranched polyglycerol HPG

As a basis for hydrogels, hyperbranched polymers [41] can also be used. These polymers can be connected by click chemistry in miniemulsion droplets in order to obtain hyperbranched polyglycerol (HPG)-based particles. Such materials are of great interest for drug release because they are nontoxic [42, 43] and show similar behavior to poly(ethylene glycol)s. 

An interesting representative of this class is hyperbranched polyglycerol (hPG) due to its high biocompatibility and water solubility (Fig. 5.16). 

FIGURE 5.16 Hyperbranched polyglycerol (hPG) and poly(ethylene imine) (PEI). 

Dimroth et al. [128] succeeded in immobilising a tethered Rh(III)-TsDPEN catalyst on hyperbranched polyglycerol (hPG), which is a suitable support due to its solubility in various solvents, high chemical stability, and weak coordination to... 

Photoswitchable supramolecular dendrimer-like structures were constructed starting from azobenzene-based and CD-based building blocks. For example a bis-azobenzene with a dipyridyl linker trans-Azo dimer) and a p-CD trimer formed an hyperbranched structure whose shape could be controlled by light (Fig. 11). AFM evidenced branched structures of several microns turning to disordered particles upon UV irradiation. Moreover a supramolecular dendrimer was recently built up in water starting from an hydrophilic hyperbranched polyglycerol with a-CD apex (CD-g-HPG) and an hydrophobic hyperbranched poly(3-ethyl-3-oxetane-methanol) with azobenzene apex (AZO-g-HPBO) (Fig. 12). The two components in 1 1 molar ratio selfassembled into a Janus-like dendrimer (JHBP, HPBO-6-HPG) of diameter ca. 5.1 nm, due to inclusion complexation of the azobenzene apex into the CD cavity of the partner... 

SCHEME 8.4 Schematic illustration of the processes involved in the graft copolymerization of DMAEMA from PVDF main chains via AGET-ATRP, preparation of PVDF-g-PDMAEMA membrane by phase inversion, and quaternization of PVDF-g-PDMAEMA membrane by propargyl bromide to produce PVDF-g-PQDMAEMA membrane with pendant aUcyne groups, covalent immobilization of hyperbranched polymer HPG-Nj or PEI-Nj onto the PVDF-g-PQDMAEMA membrane surface via surface alkyne-azide click reaction. PVDF, poly(vinylidene fluoride) DMAEMA, 2-(V, V-dimethylamino)ethyl methacrylate VC = L-ascorbic acid PMDETA = V,V,M,V, A"-pentamethyl diethylene triamine HPG-N3 = az/hyperbranched polyglycerols PEI-N3 = azirfo-polyethylenimine. Reprinted with permission from Reference 114. Copyright 2013 American Chemical Society. 

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