Stimuli-Responsive Tertiary Amine Functional PEGs Based on N,N-Dialkylglycidylamines

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• 作者：Jana Herzberger ; Dennis Kurzbach ; Mathias Werre ; Karl Fischer ; Dariush Hinderberger ; Holger Frey
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：November 25, 2014
• 年：2014
• 卷：47
• 期：22
• 页码：7679-7690
• 全文大小：562K
• ISSN：1520-5835

文摘

Amine-functional poly(ethylene glycol) (PEG) copolymers have been prepared that exhibit thermo- and pH- responsive behavior in aqueous solution. Three novel tertiary di(n-alkyl)glycidylamine monomers have been introduced for anionic ring-opening copolymerization (AROcP) with ethylene oxide (EO): N,N-di(n-butyl)glycidylamine (DButGA), N,N-di(n-hexyl)glycidylamine (DHexGA), and N,N-di(n-octyl)glycidylamine (DOctGA). Via controlled AROcP we synthesized well-defined (M_w/M_n = 1.05鈥?.14), water-soluble block- and gradient-type PEG copolymers, containing up to 25 mol % of the respective dialkylglycidylamine comonomer. Molecular weights ranged from 4900 to 12鈥?00 g mol^鈥?. Detailed in-situ ¹H NMR kinetics and ¹³C triad analyses elucidate the microstructures of the copolymers and the relative reactivity of the novel comonomers. Notably, the n-alkyl chain length had no significant influence on the relative reactivity of the glycidylamine comonomers. Calculated reactivity ratios ranged from r_EO = 1.84, r_DButGA = 0.49 to r_EO = 1.78, r_DOctGA = 0.42, manifesting the formation of gradient copolymers. Thermo- and pH-responsive properties of these copolymers are precisely tunable by the comonomer ratio, and cloud points in aqueous solution can be adjusted between 21 and 93 掳C. Electron paramagnetic resonance (EPR) spectroscopic studies with TEMPO as a spin probe were conducted to elucidate host鈥揼uest interactions of the copolymers. Unexpectedly, the n-alkyl chain length of the different glycidylamine comonomers only influences the inverse phase transition of the gradient copolymers, but not of the block copolymers on the nanoscale. Self-assembly of the block- and gradient-type copolymers in aqueous alkaline solution by both static and dynamic light scattering has also been investigated after confirming the existence of pure unimers in methanol.