Polyglycerol, hyperbranched

General Procedure for the Stepwise Hydroformylation/Reductive Amination on Allylated Hyperbranched Polyglycerols (PG). Synthesis of Hydroaminomethylated Hyperbranched PG-dendrimers. PG-Allyl, Rh(acac)(CO)2 and XANTPHOS were dissolved in dry toluene and placed in an autoclave. The autoclave was pressurized with CO/H2 (1 1, 30 bar), heated at 70 °C for 5d. After cooling, the amine was added to the crude PG-aldehyde (1H NMR was used to confirm full conversion) and stirred for 1-2 h. After stirring, Rh(acac)(CO)2 was added and the autoclave was pressurized with CO/H2 (1 6, 70 bar) and heated at 85 °C for 2-5 days. After cooling, the solvent was removed in vacuo and the crude mixture was purified by dialysis (benzoylated cellulose tubing) to give the re-... 

Scheme 18 Amination of allylated hyperbranched polyglycerols via hydroaminomethyla-tion... 

Scheme 6.11 Synthesis of hyperbranched polyglycerol polymers with terminal palmitoyl groups.

The same hyperbranched polyglycerol modified with hydrophobic palmitoyl groups was used for a noncovalent encapsulation of hydrophilic platinum Pincer [77]. In a double Michael addition of ethyl cyanoacetate with methyl vinyl ketone, these polymer supports indicated high conversion (81 to 59%) at room temperature in dichloromethane as a solvent. The activity was stiU lower compared with the noncomplexed Pt catalyst. Product catalyst separation was performed by dialysis allowing the recovery of 97% of catalytic material. This is therefore an illustrative example for the possible apphcation of such a polymer/catalyst system in continuous membrane reactors. 

Finally, first attempts were made to extend the concept of soluble hyperbranched polymers to dendronized sohd-phase materials. Recently, the first dendronized sohd phase, accessible in only one reaction step was reported (Fig. 7.4) [36]. The coupling of hyperbranched polyglycerol to Merrifield resin yields a new type of high-loading sohd-phase hybrid material with loading capacities of ca. 3 mmol g and good swelling properties even in protic solvents (see also Section 3.4). 

A first example of a polystyrene dendronized with a hyperbranched polymer was recently reported by Stumbe and Haag [36]. They synthesized a polystyrene-polyglycerol hybrid support (61) by coupling a hyperbranched polyglycerol (15)... 

Fig. 4 Examples (a) PEGylated monolayer (b) Glucose-modified monolayer (c) Surface-attached hyper-branched polyethylene imine and (d) Surface-attached hyperbranched polyglycerols of surface-coatings that resist the nonspecific adsorption of proteins. (Figure reproduced in part with permission from [41])...

Frey and Van Koten et al. [40-42] reported on the noncovalent encapsulation of sulfonated pincer-platinum(II) complexes in readily available amphiphilic nanocapsules based on hyperbranched polyglycerol, possessing a reverse micelle-type architecture. The incorporated platinum(II) complexes showed catalytic activity in a double Michael addition, albeit with decreased activities compared to the free pincer complex. Due to the size of... 

Fig. 13 a Synthesis of dendritic polyglycerol perfluorolkyl ester 18 from hyperbranched polyglycerol 17... 

Scheme 1 Structure of hyperbranched polyglycerol and oxidative coupling reaction of phenylacetylene...

Scheme 2 Synthesis of pertosylated hyperbranched polyglycerol followed by partial substitution of tosyl groups with NCN-pincer platinum(II) carboxylates...

Recently, we used hyperbranched polyglycerol 1 as a high-loading support for boronic acids with application in the palladium-catalyzed Suzuki cross-coupling reaction [79]. Moreover, hyperbranched polyglycerol (1) can... 

Amphiphilic modification of hyperbranched polyglycerol (1) or polyethylene imine) by partial esterification or, respectively, amidation with fatty acids results in macromolecules with a nonpolar shell and a polar core. Metal nanoparticles are stabilized efficiently by these materials, because the polar moieties are responsible for adsorption to the particle surface and the nonpolar region also convey solubility in nonpolar organic solvents [17,94,95]. 

In Sect. 2 of this overview, the NCN-pincer platinum(II) complex was covalently attached to hyperbranched polyglycerol by substitution of tosylate groups to obtain catalyst 4. This NCN-pincer platinum complex may also be noncovalently immobilized on polyglycerols, and the activity/selectivity of these systems in catalytic reactions has been investigated. 

In this context, the chiral hyperbranched polyglycerols (-)-PG [Mn = 3000, with bis(2,3-dihydroxypropyl)undecenylamine as the initiator] and (+)-PG [Mn = 5500, with trimethylolpropane (TMP) as the initiator] were used. Esterification of the hydroxyl groups of these hyperbranched polyglycerols with hydrophobic alkyl chains as palmitoyl chloride, yielded amphiphilic molecular nanocapsules with reverse micelle-type architecture, in which approximately 50% of the hydroxyl groups were functionalized with palmitoyl chains [96-98]. These materials exhibit low polydispersity (Mw/Mn < 2), and the amphiphilic molecular nanocapsules are soluble in nonpolar solvents and irreversibly encapsulate various polar, water-soluble dye molecules in their hydrophilic interior by liquid-liquid extraction [96,98]. 

Sunder, A., Hanselmann, R., Frey, H., and Mulhaupt, R. 1999. Controlled synthesis of hyperbranched polyglycerols by ring-opening multibranching polymerization. Macromolecules, 32, 4240 1246. 

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. 

Kainthan RK, Brooks DE (2007) In vivo biological evaluation of high molecular weight hyperbranched polyglycerols. Biomaterials 28(32) 4779-4787... 

Kainthan RK, Muliawan EB, Hatzikiriakos SG, Brooks DE (2006) Synthesis, characterization, and viscoelastic properties of high molecular weight hyperbranched polyglycerols. Macromolecules 39(22) 7708-7717... 

The hyperbranched polyglycerols were used successfully as copolyols for rigid PU foams and after the alkoxylation of polyglycerols with PO and EO. Higher molecular weight polyether polyols used for elastic PU were obtained [16]. 

Figure 19.3 Hyperbranched polyglycerol with 20 glycidol units (pseudodendrimer) [11-14]...

Recently, Haag and coworkers reported on the synthesis of polystyrene beads dendronised with a hyperbranched polymer [66, 67]. The polystyrene-polyglycerol hybrid support 5 was obtained by grafting of a hyperbranched polyglycerol directly onto a Merrifield resin [67] or alternatively polymerising glycidol directly onto a polyhydroxylated crosslinked polystyrene... 

The dominant contribution of simultaneous chain growth from all the chain ends, controlled by the deprotonation level of the initiator, leads to relatively narrow MWD B 1.1-1.4) while maintaining branching levels typical of random polycondensation reactions (degree of branching a 0.5, Eq. 30.7) [70]. The SCROP technique has also been used to synthesize hyperbranched polyglycerols [70], polyethers [71], and polyamines [72]. 

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