Thermo‐Responsive Nanogels Based on Poly[NIPAAm‐graft‐(2‐alkyl‐2‐oxazoline)]s Crosslinked in the Micellar State

Abstract

Graft copolymers with thermo‐sensitive PNIPAAm backbone and hydrophilic PEtOxa graft chains demonstrated typical amphiphilic behavior. For specific compositions stable micelle‐like aggregates were formed depending on the temperature. Applying long polyoxazoline side chains ($\overline {DP} $ > 120), stable reversible micelle‐like aggregates with hydrodynamic radii of 30–40 nm could be obtained between 33 and 55 °C. These graft copolymers have been successfully crosslinked by electron‐beam irradiation in the micellar state yielding core/shell type nanogels with thermo‐reversible swelling behavior. The temperature dependent volume change of the new thermo‐responsive nanogels due to the phase transition of the PNIPAAm core has been verified by DLS.magnified image

New Thermo‐Sensitive Graft Copolymers Based on a Poly(N‐isopropylacrylamide) Backbone and Functional Polyoxazoline Grafts with Random and Diblock Structure

“…Recently [14,15] we reported on the synthesis and characterization of new graft copolymers based on a polyNIPAAm main chain and poly(2-methyl-2-oxazoline) (polyMeOxa) or polyEtOxa grafts with varying number and length of the graft arms synthesized through the ''grafting from'' method. For this, the ''living'' cationic polymerization of the MeOxa or EtOxa was initiated through a statistic copolymer of NIPAAm and chloromethylstyrene (CMS).…”

“…At a balanced relation of both components the graft copolymers forms stable aggregates over a wide temperature range. [14,15] For extending this approach, now additional COOH groups had been incorporated in the polyEtOxa graft arms. Based on the living character of oxazoline polymerization in a first step side chains based on random and diblock copolymers of EtOxa and 2-(2-methoxycarbonylethyl)-2-oxazoline (MEtOxa) were synthesized with varying comonomer content.…”

Design Strategies for Functionalized Poly(2-oxazoline)s and Derived Materials

“…In solution, core-shell nanogels with micellar shape and reproducible thermo-and pH-dependent swelling behavior formed, which could be stabilized by electron-beam crosslinking. Grafting of pEtOx from the copolymer composed of N-isopropylacrylamide and chloromethylstyrene yielded thermoresponsive nanogels (in solution) that responded with volume changes to temperature changes [106].…”

Synthesis and characterization of new pH- and thermo-responsive hydrogels based on N-isopropylacrylamide and 2-oxazolines

“…[18] The iodomethylstyrene initiates the polymerization of MEtOxa and MeOxa, and because the reactivity of these monomers is similar [21][22][23] finally a statistical copolymer of these monomers is formed which contains a vinyl group at the one chain end (starting group) and a OH group at the other chain end, because the polymerization has been terminated by KOH in methanol. [32] The structure of MM was confirmed by 1 H NMR spectroscopy.…”

“…[10,11] Some polyoxazolines, as polymethyloxazoline, have hydrophilic character while others, as for example polynonyloxazoline, have hydrophobic character. In recent years, our research group has developed, based on NiPAAm and 2-oxazolines, different polymer structures soluble in water and sensitive to temperature and pH, [20][21][22][23] which formed stable and reversible micelles, and the formation of double-responsive nanogels by irradiation with electrons was demonstrated.…”