Product Information Polyglycerol

Introduction: Dendritic Polymers

Dendritic polymers are materials with a highly branched structure. They combine unique chemical and physical properties. Due to the large number of endgroups - one at every end of a branch - they are highly functional. The high degree of branching prevents crystallization. The materials are soluble in numerous organic solvents. Furthermore, the high degree of branching renders entanglement of the polymers impossible, which results in low melt and solution viscosity.
Over the past decade, perfect dendrimers have received immense interest from academic as well as industrial researchers. However, commercial applications of these perfectly branched materials are scarce, since the tedious multistep synthesis result in inacceptable costs for most applications.


Schematic comparison between a perfect dendrimer and a hyperbranched polymer with a central core (o) and multiple functional endgroups () in the periphery.

The so-called hyperbranched materials also contain a large number of branches. However, they are not perfectly (i.e. absolutely regularly) branched. In this respect their structure can be compared to a tree, which also contains larger and smaller branches. In contrast to dendrimers, hyperbranched polymers can be prepared conveniently in one-step procedures. However, due to extremely broad molecular weight distributions and undesired side reactions, such polymers were regarded as very ill-defined materials. The simultaneous presence of large fractions of low molecular weight compounds and high molecular weight polymers is inacceptable for most applications.



Hyperbranched Polyglycerol


Synthesis Only recently, a synthetic route enabling the preparation of well-defined hyperbranched polyglycerols was discovered in Freiburg. A proprietary process affords polyglycerols with narrow molecular weight distribution (Mw/Mn < 1.5) and defined molecular weights in the range of 1.000 to 30.000 g/mol.


Currently, the production process is run on a kilogramm scale. There are no basic concerns or prohibitions regarding further scale-up, and the technical realization is in progress




Chemical properties and structure. Hyperbranched polyglycerol possesses an inert polyether scaffold. Each branch ends in a hydroxy-function, which renders hyperbranched polyglycerol a highly functional material, e.g., a molecule with a molecular weight of 5000 g/mol possesses 68 hydroxyl end groups.


Structure of a hyperbranched polyglycerol with 20 monomer units.


The high functionality in combination with the versatile and well-investigated reactivity of hydroxyl-functions is the basis for a variety of derivatives. Partial esterification with fatty acids yields amphiphilic materials, which behave as nanocapsules. Such nanocapsules can, for example, incorporate polar molecules as guests and solubilize them in an apolar environment. Selective modification can be achieved utilizing the reactivity of 1,2-diol units, located preferentially at the periphery of the molecule. Complementary to functionalization by reactions of the large number of hydroxy-groups, a single functionality can also be introduced selectively as the 'core' of the molecule. A number of single core functionalities, such as a vinylic group, amines and thiols, have been incorporated.

As alluded to, by using an appropriate protocoll for their synthesis hyperbranched polyglycerols can be prepared with controlled molecular weights. Molecular weights currently available are in the range of 1.000 up to 30.000 g/mol (true molecular weights, determined by various methods). Molecular weight distributions are narrow, that is the apparent polydispersity Mw/Mn is usually below 1.5 (determined by size exclusion chromatography vs. polypropyleneoxide standards).



Physical properties. Hyperbranched polyglycerol is a clear, viscous liquid. The glass transition temperature is considerably below room temperature, typically around Tg -25 °C. At room temperature it is highly viscous, the viscosity increasing with molecular weight. By simple heating to slightly elevated temperatures (80°C) it behaves like a free-flowing liquid. Hyperbranched polyglycerol is highly soluble in water and also polar organic solvents, such as methanol. By comparison to linear, non-branched polymers solution-viscosity is considerably lower. Polyglycerols are essentially non-volatile at room temperature.


Biocompatibility is one particularly advantageous feature of aliphatic polyether structures, such as polyglycerol. Thus, an essential prerequisite for applications as a delivery agent for biologically active compounds, cosmetics etc. is provided. In containing hydroxy-endgroups and a polyether-backbone, the hyperbranched polyglycerols resemble the well-known linear polyethylene glycols (PEG, PEO) which are approved for a large variety of medical and biomedical applications.




Hyperbranched Polyethylenimine



Dendritic polyethylenimine is a highly functional aliphatic polyamine with a globular structure. It has a degree of branching between 65-75% and relatively narrow polydispersities (ca. 1.3 for PEI-5 and ca. 2.5 for PEI-25). It is a transparent colorless viscous liquid with a low intrinsic viscosity in solution.





Bibliography

Synthesis and Monofunctionalization of hyperbranched polyglycerol

Sunder, A., Hanselmann, R., Frey, H., Mülhaupt, R., Controlled Synthesis of Hyperbranched Polyglycerols by Ring-Opening Multibranching Polymerization, Macromolecules, 1999, 32, 4240-4246.

Sunder, A., Mülhaupt, R., Haag, R., Frey, H., Chiral Hyperbranched Dendron-Analogs, Macromolecules, 2000, 33, 253-254.

Molecular nanocapsules; use as templates

Sunder, A., Krämer, M., Hanselmann, R., Mülhaupt, R., Frey, H., Molecular Nanocapsules Based on Amphiphilic Hyperbranched Polyglycerols, Angew. Chem. 1999, 111, 3758; Int. Ed. Engl. 1999, 38, 3552.

Mecking, S., Thomann, R., Frey, H., Sunder, A., Preparation of Catalytically Active Palladium Nanoclusters in Compartments of Amphiphilic Hyperbranched Polyglycerols, Macromolecules 2000, 33, 3958.

Mecking, S., Schlotterbeck, U., Thomann, R., Soddemann, M., Stieger, M., Richtering, W., Kautz, H., Formation of Metal Nanoparticles in Modified Hyperbranched Polyglycerols and Use as Soluble Separable Catalysts, Polym. Mat. Sci. Eng. 2001, 84, 511 - 512.

Haag, R., Krämer, M., Stumbé, J.-F., Kautz, H., Polymeric Nanocapsules based on Core-Shell-Type Architectures in Hyperbranched Polyglycerols, Poly. Mat. Sci. Eng., 2001, 84, 69.

Krämer, M., Stumbé, J.-F., Türk, H., Krause, S., Komp, A., Delineau, L., Prokohova, S., Kautz, H, Haag, R., pH-Responsive Molecular Nanocarriers Based on Dendritic Core-Shell Architectures, Angew. Chem. 2002, 114, 4426-4431; Angew. Chem. Int. Ed. 2002, 41, 4252-4256.

Garcia-Bernabé, A., Krämer, M., Olah, B., Haag, R., Phase Transfer Properties of Perfluorinated Dendritic Core-Shell Architectures, Chem. Eur. J. 2004, 10, 2822-2830.

Dendritic Polyglycerols as Support for Organic Synthesis

Haag, R., Sunder, A., Hebel, A., Roller, S., Dendritic Aliphatic Polyethers as High-loading Soluble Supports for Carbonyl Compounds and Parallel Membrane Separation Techniques, J. Combinatorial Chem. 2002, 4, 112-119.

Hebel, A., Haag, R., Polyglycerol as High-Loading Support for Boronic Acids with Application in Solution-Phase Suzuki Cross-Couplings, J. Org. Chem. 2002, 67, 9452-9455.

Roller, S., Siegers, C., Haag, R., Dendritic Polyglycerol as High-Loading Support for Parallel Multistep Synthesis of GABA Lactam Analogues, Tetrahedron 2004, 60, 8711-8720.

Derivativization of polyglycerol

Sunder, A.; Quincy, M.-F.; Mülhaupt, R., Frey, H. Hyperverzweigte Polyetherpolyole mit flüssigkristallinen Eigenschaften, Angew. Chem., 1999, 111, 3107; Angew. Chem. Int. Ed. Engl. 1999, 38, 2928.

Sunder, A.; Mülhaupt, R. Frey, H. Polyether-Polyols Based on Hyperbranched Polyglycerol: Polarity Design by Block Copolymerization with Propylene Oxide; Macromolecules, 2000, 33, 309.

Knischka, R.; Lutz, P. J.; Sunder, A.; Mülhaupt, R.; Frey, H. Functional PEO-Multiarm Star Polymers: Core-First Synthesis Using Hyperbranched Polyglycerol Initiators, Macromolecules, 2000, 33, 315.

Sunder, A.; Bauer, T.; Mülhaupt, R.; Frey, H. Synthesis and Thermal Behavior of Esterified Aliphatic Hyperbranched Polyether Polyols, Macromolecules, 2000, 33, 1330.

Burgath, A.; Sunder, A.; Mülhaupt, R.; Neuner, I.; Frey, H.; PCL-Multiarm star polymers based on polyglycerol; Macromol. Chem. Phys., 2000, 201, 792.

Maier, S.; Sunder, A.; Frey, H.; Mülhaupt, R. Synthesis of Poly(methylacrylate) Multi-arm Star Polymers on the Basis of Hyperbranched Polyglycerol Core, Macromol. Rapid Commun. 2000, 21, 226.

Haag, R.; Stumbé, J.-F.; Sunder, A.; Frey, H.; Hebel, A. An Approach to Core-Shell-Type Architectures in Hyperbranched Polyglycerols by Selective Chemical Differentiation; Macromolecules, 2000, 33, 8158-8166.


Protein resistant surface modifications

Siegers, C., Bisalski, M., Haag, R. Protein Resistant Self-Assembled Monolayers of Dendritic Polyglycerol Derivatives on Gold, Chem. Eur. J. 2004, 10, 2831-2838.


Dendritic Polyglycerol Sulfates as Potent Heparin Analogs

Türk, H., Haag, R., Alban, S. Dendritic Polyglycerol Sulfates as New Heparin Analogues and Potent Inhibitors of the Complement System, Bioconjugate Chem. 2004, 15, 162-167

Polyglycerol copolymers

Sunder, A.; Türk, H.; Haag, R.; Frey, H. Copolymers of glycidol and glycidyl ethers: design of branched polyether-polyols by combination of latent cyclic AB2 and ABR monomers, Macromolecules 2000, 33, 7682.

Polyglycerol-dendrimers and Pseudodendrimers

Haag, R.; Sunder, A.; Stumbé, J.-F. An approach to glycerol dendrimers and pseudo-dendritic polyglycerols, J. Am. Chem. Soc., 2000, 122, 2954-2955.

Stumbé, J. F.; Sunder, A.; Haag, R., Pseudo-Dendrimers as an Alternative to Perfect Dendrimers: A General Concept, Poly. Mat. Sci. Eng. 2001, 84, 1023-1024.

Dendritic Polyethylenimines for Gene Transfections

Krämer, M., Stumbé, J.-F., Grimm, G., Krüger, U., Kaufmann, B., Weber, M., Haag, R., Dendritic Polyamines: A Simple Access to new Materials with Defined Tree-like Structures for Application in Non-Viral Gene Delivery, ChemBioChem 2004, 5, 1081-1087.

Metal particle synthesis, catalysis and membrane separation

Mecking, S., Thomann, R., Frey, H., Sunder, A., Preparation of Catalytically Active Palladium Nanoclusters in Compartments of Amphiphilic Hyperbranched Polyglycerols. Macromolecules 2000, 33, 3958 - 3960.

Aymonier, C., Schlotterbeck, U., Antonietti, L., Zacharias, P., Thomann, R., Tiller, J.C., Mecking, S., Hybrids of Silver Nanoparticles with Amphiphilic Hyperbranched Macromolecules Exhibiting Antimicrobial Properties. Chem. Commun. 2002, 3018 - 3019.

Sablong, R., Schlotterbeck, U., Vogt, D., Mecking, S. Catalysis with Soluble Hybrids of Highly Branched Macromolecules with Palladium Nanoparticles in a Continuously Operated Membrane Reactor. Adv. Synth. Catal. 2003, 345, 333 - 336.

Garamus, V.M., Maksimova, T.V., Richtering, W., Kautz, H., Frey, H., Schlotterbeck, U., Mecking, S. Hyperbranched Polymers: Structure of Hyperbranched Polyglycerol and Amphiphilic Polyglycerolesters in Dilute Aqueous and Non-aqueous Solution. Macromolecules 2004, 37, 8394 – 8399.


Reviews

Sunder, A.; Heinemann, J.; Frey, H. Controlling the growth of polymer trees: concepts and perspectives for hyperbranched polymers, Chem. Eur. J. 2000, 6, 2499.

Sunder, H.; Mülhaupt, R.; Haag, R.; Frey, H. Hyperbranched Polyether Polyols: A Modular Approach to New Materials with Complex Polymer Architectures, Adv. Mater. 2000, 12, 235.

Haag, R., Dendrimers and Hyperbranched Polymers as High-Loading Supports for Organic Synthesis, Chem. Eur. J. 2001, 7, 327-335.

Frey, H.; Haag, R. Dendritic Polyglycerol: A New Versatile Biocompatible Material, Rev. Mol. Biotech. 2002, 90, 257-267