PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 16229513

Biomimetic stimulus-responsive star diblock gelators.

Yuting Li·Yiqing Tang·Ravin Narain·Andrew L Lewis·Steven P Armes
View original source ↗Export metadata ↓

Abstract

Novel biomimetic gelators with star diblock copolymer architectures have been synthesized by atom-transfer radical polymerization (ATRP). Two types of trifunctional ATRP initiator were used to polymerize 2-(methacryloyloxy)ethyl phosphorylcholine [MPC] at 20 degrees C, followed by sequential monomer addition of various tertiary amine methacrylates or mixtures thereof. Poor living character was achieved using an amide-based trifunctional initiator, but the analogous triester initiator gave reasonably well-defined thermo-responsive and pH-responsive star diblock copolymers. The most effective thermo-responsive gelators were obtained by the statistical terpolymerization of 2-(dimethylamino)ethyl methacrylate [DMA], 2-(diethylamino)ethyl methacrylate [DEA], and a monomethoxy-capped poly(propylene oxide) methacrylate [PPOMA], whereas pH-responsive gelators were prepared using 2-(diisopropylamino)ethyl methacrylate [DPA] as the second monomer. Star diblock copolymer gelators that were both thermo-responsive and pH-responsive were obtained by the statistical copolymerization of DMA with DPA. Copolymer compositions were assessed by 1H NMR spectroscopy, and the molecular weight distributions of the three-arm star MPC homopolymer precursors were assessed by aqueous gel permeation chromatography. Static light scattering was used to obtain weight-average molecular weights of selected star diblock copolymers and rheological measurements and variable-temperature 1H NMR were used to probe the onset of gelation.

Explore related subjects

BiomimeticsCatalysisChromatographyGelsHydrogen-Ion ConcentrationLightMagnetic Resonance SpectroscopyMethacrylatesNylonsPhosphorylcholinePolymersPolymethacrylic AcidsRheologyTime FactorsJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Yuting Li, Yiqing Tang, Ravin Narain, Andrew L Lewis, Steven P Armes. 2005-10-25. Biomimetic stimulus-responsive star diblock gelators.. https://doi.org/10.1021/la050356u

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Dissecting the general physicochemical properties of noncovalent interactions involving tyrosine side chain as a second-shell ligand in biomolecular metal-binding site mimetics: an experimental study combining fluorescence, 13C NMR spectroscopy and ESI mass spectrometry.

Detailed physicochemical features inherent in the dynamic cation-pi interactions of aromatic amino acid side chains in the secondary coordination spheres around metal ions were extracted and mapped by intrinsic tyrosine fluorescence titration experiments with two homologous, artificially engineered metal-binding scaffolds which mimic metal-binding sites in metalloproteins. A newly formulated method for the treatment of fluorescence titration data allows straightforward assessment of both the magnitudes and properties of metal-chelation-assisted cation-aromatic interactions (K2) underlying a proposed two-step metallosupramolecular association process. The unprecedented linear platform-motif correlations between the two contrasting scaffolds in their changes in tyrosine fluorescence on binding of 3d metal cations help to elucidate the properties of general cation-arene recognition corresponding to the metal-responsive characteristics of the second-shell Tyr residue surrounding the metal-binding sites in the supramolecular context, and thereby define a new noncovalent design principle for metal-ion recognition in aqueous solution. As supported by NMR spectroscopic and ESI-MS analyses and molecular mechanics force field calculations, the systematic study exemplifies the concept of using steady-state tyrosine fluorescence as a powerful tool for comprehensive descriptions of cation-pi interactions in the extended environment of a metal-binding site. We established that the physicochemical properties pertaining to indirect metal-arene interactions are highly dependent on the electronic properties of the metal ions. This work suggests that second-shell cation-pi interactions may play more diverse roles, including modulation of structure, reactivity, and function of metal-binding sites, than the previously well-established direct cation-pi interactions involving hard cations (e.g., alkali metal ions). Moreover, such a study will continue to complement theoretical predications and/or the early experimental investigations in organic solvents.

Biomimetics↗