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Magnetic and Temperature‐Sensitive Release Gels from Supramolecular Polymers
Author(s) -
Binder W. H.,
Petraru L.,
Roth T.,
Groh P. W.,
Pálfi V.,
Keki S.,
Ivan B.
Publication year - 2007
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200601084
Subject(s) - materials science , polymer , ethylene glycol , hydrodynamic radius , chemical engineering , dynamic light scattering , nucleation , supramolecular chemistry , ethylene oxide , superparamagnetism , lower critical solution temperature , radius of gyration , supramolecular polymers , magnetic nanoparticles , polymer chemistry , dynamic mechanical analysis , peg ratio , nanoparticle , molecule , nanotechnology , magnetization , composite material , organic chemistry , copolymer , chemistry , magnetic field , engineering , quantum mechanics , physics , finance , economics
Abstract Supramolecular gels consisting of trivalent polyisobutylene and bivalent poly(ethylene oxide) are generated. Strong hydrogen bonding interactions, affixed to the end‐group moieties of the respective polymers (binding constant K assn = 10 5 M –1 ), serve as molecular glue, leading to the formation of weak gels. Two different gels were prepared: one, with a short telechelic poly(ethylene glycol) (PEG) segment (gel A), and one with a longer PEG segment (number‐average molecular weight M n = 2000 g mol –1 ) (gel B). Both gels show a significant increase in viscosity upon mixing of the two polymeric components, with a lag time of several minutes, indicative of nucleation mechanisms as the formation principle. However, only gel A displays classical gel‐like behavior, with a loss modulus G ′ larger than the storage modulus G ″ after formation. Both gels display microphase‐separated behavior with a spacing between 4–5 nm as probed via small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) measurements. The incorporation of magnetic nanoparticles (Fe 2 O 3 ; radius r = 3.5 nm) is successfully achieved, generating new magnetic gels with strongly thermoresponsive properties, displaying a strong temperature‐dependent release profile of included dye molecules. Magnetic measurements indicate a superparamagnetic behavior of the incorporated nanoparticles, prospecting the application as magneto‐sensitive delivery gels for pharmaceutical purposes.