| PROPERTIES |
Carbon-13 NMR spectroscopy, matrix-assisted laser desorption ionization time-of-flight mass specstroscopy, vapor pressure osmometry, & GPC are used to determine the MW & polydispersities of the polyglycerols The degree of branching (DB) of these structures is calculated from Carbon 13 NMR data using mathematical expression previously derived by the team. For a linear structure DB = 0, whereas for perfect dendrimers it is 1. The values for the present hyperbranched polyglycerols, which incorporate both branched & linear units is 0.53-0.59. The polymers have a very compact structure compared with linear polymers because of the high degree of branching. The high number of -OH make the polymer water soluble, on one hand, &, on the other hand, allow for a variety of functionalization, for example, for the formation of esters, urethanes |
| SYNTHESIS |
The group reports the use of strategy termed "ANIONIC RING-OPENING MULTIBRANCHING POLYMN" for the controlled synthesis of hyperbranched polyglycerol from glycidol. The group demonstrated that branched polyglycerols can be prepd on a large scale using GLYCIDOL which is a commercial monomer. They perform the synthesis on a 50-g scale The strategy leads to polydispersities < 1.5 & mostly < 1.25. It represents the first case of a controlled process for the synthesis of hyperbranched polymers Glycidol is a highly reactive hydroxy epoxide. As a monomer, it can be classified a latent AB2 type, where A & B are complementary reactive groups that link when polymerized. Polymn of glycidol using present strategy leads to a hyperbranched polyether scaffold with numerous hydroxyl end groups that are located not only at the surface of the polymer but also, unlike DENDRIMER scaffolds throughout the structure. The polymers are known as POLY GLYCEROLS A partially deprotonated triol is used as an anionic alkoxide initiator for the anionic polymn. The initiator reacts with a glycidol monomer to form a monofunctional local core unit in the hyperbranched polymer. In the subsequent propagation steps, the alkoxide initiator reacts with the unsubstituted end of the epoxide ring to generate further anionic alkoxide end groups thart are in dynamic equilibrium with the OH end groups. The low polydispersities are achieved by adding the monomer slowly. The method leads to complete incorporation of the alkoxide initiator into the hyperbranched polymer. The degree of polymn is controlled by varying the ratio of initiator & monomer. The strategy enables the control of concn of active sites - the alkoxides - in the polymn, leading to simultaneous growth of all chain ends & thus control the MW & considerable narrowing the polydispersity |
| UPDATE | 09.99 |
| USES |
Biomedical applications - for example, for controlled drug release, targeting & diagnostics Catalysis |
| AUTHOR | This data is not available for free |
| LITERATURE REF. | This data is not available for free |
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