Polymerization of long chain alkyl glycidyl ethers: a platform for micellar gels with tailor-made melting points. Issue 44 (22nd October 2018)

• Record Type: Journal Article
• Authors: Verkoyen, Patrick; Johann, Tobias; Blankenburg, Jan; Czysch, Christian; Frey, Holger
• Is Part Of: Polymer chemistry. Volume 9:Issue 44(2018)
• Page Start: 5327
• Page End: 5338
• Publication Date: 2018-10-22
• Subjects: Polymers -- Periodicals; Macromolecules -- Periodicals; Polymerization -- Periodicals; 547.705
• DOI: 10.1039/c8py01312h
• Languages: English
• ISSNs: 1759-9954

Abstract

Abstract : Controlled polymerization of long-chain alkyl glycidyl ethers (AlkGE) under anionic ring opening conditions is enabled by the addition of 18-crown-6. Capitalizing on this strategy, highly amphiphilic block copolymers are prepared that form hydrogels with adjustable melting points. Abstract : Controlled polymerization of long-chain alkyl glycidyl ethers (AlkGE) under anionic ring opening polymerization conditions is enabled by the addition of a crown ether (18-crown-6, K + ). Homopolymers with molecular weights in the range of 4000 to 9000 g mol −1 and side chain melting temperatures of 14 °C (C12 -AlkGE) and 43 °C (C16 -AlkGE), respectively were synthesized. Furthermore, a series of amphiphilic ABA polyether triblock copolymers with polyethylene glycol (PEG) as the hydrophilic central block ( M n = 6k, 10k, and 20k g mol −1 ) with total molecular weights in the range of 7000 to 28 000 g mol −1 and narrow dispersity (1.12 to 1.34) were prepared. Separate melting endotherms of the triblock copolymers were observed for these double-crystalline materials. Due to self-assembly of the hydrophobic alkyl chains, the addition of water or water/ethanol mixtures to the triblock copolymers leads to the formation of micellar, one-component hydrogels. By varying the repeating units of the hydrophobic PAlkGE blocks, a tunable hydrophobic effect can be achieved. Variation of the alkyl chain length enables tailoring of the melting temperatures of the PAlkGE-blocks both in bulk and hydrogels. Thermal and rheological investigation of ethanol/water gels revealed temperature-dependent mechanical behavior, indicating a transition from crystalline to flexible micellar hydrophobic domains in the range of 12 °C to 31 °C. The amphiphilic polyether triblock copolymers enable the preparation of guest-loaded thermo-responsive gels and hydrogels and bear promise for pharmaceutical applications, e.g. as drug release systems.