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

Abstract

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 = 1.05–1.14), water-soluble block- and gradient-type PEG copolymers, containing up to 25 mol % of the respective dialkylglycidylamine comonomer. Molecular weights ranged from 4900 to 12 000 g mol–1. 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 °C. Electron paramagnetic resonance (EPR) spectroscopic studies with TEMPO as a spin probe were conducted to elucidate host–guest 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.

Oxidation-Responsive and “Clickable” Poly(ethylene glycol) via Copolymerization of 2-(Methylthio)ethyl Glycidyl Ether

“…This trend is most distinct for the random PEG-ran-PMTEGE copolymers and is frequently observed for multi-functional PEGs. [27][28][29] EO/MTEGE ratios were also calculated from 1 H NMR spectra comparing the signal of the methyl group (-SCH 3 ) at 2.15 ppm to the polyether backbone signal at 3.4-3.8 ppm (Figure 2 and S7). Overall, ratios were varied from 3-24 mol%, yielding water-soluble polymers while preserving PEG's outstanding properties, and increasing its functionality ( Table 1).…”

“…Random PEG-ran-PMTEGE copolymers with MTEGE ratios of 5-24 mol% are water soluble at room temperature, but turbid solutions are observed when samples are heated to a specific temperature. This so called "thermoresponsiveness" is a common feature of multi-functional PEGs, that bear hydrophobic units distributed along the polymer backbone, rendering them attractive for drug delivery applications 28,35. PEG itself is fully water-soluble up to ~ 100 °C, due to the specific bond distance of its oxygen atoms, which allows for beneficial hydrogen bonding with water 36.…”

Optical properties of amphiphilic copolymer-based self-assemblies

“…The stimuli-responsive property is defined as the ability of the system undergoing sharp responses to chemical changes or environmental changes such as pH, temperature, light, and redox [82][83][84][85]. Among the available stimulis, light has attracted special attention since it can be localized in time and space, and triggered from outside of the system [86].…”

Capitalizing on Protecting Groups to Influence Vinyl Catechol Monomer Reactivity and Monomer Gradient in Carbanionic Copolymerization

“…In the current work we examined a variety of novel catechol‐based vinyl monomers with systematically varied acetal protecting groups, employing linear, branched, or cyclic ketones to generate the acetal structures. Fundamental properties of the polymers can be changed in this manner . However, the main focus of this work is placed on the influence of the protecting group structure on carbanionic copolymerization kinetics and the resulting copolymer structure.…”