Hydrophilic arborescent polymers by radical polymerization

Höhner, Julian Robin; Möller, Martin (Thesis advisor); Pich, Andrij (Thesis advisor)

Aachen : RWTH Aachen University (2022)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2022

Abstract

In this thesis, water soluble hydrophilic arborescent polymers and arborescent copolymers are synthesized. Water soluble hydrophilic arborescent polymers of up to G3 are achieved in a grafting-from reaction scheme relying on copper mediated reversible deactivation radical polymerization (Cu-mediated RDRP). Living polymerization conditions and the reaction scheme allow the prediction of molecular weight. Arborescent poly((N-isopropyl acrylamide)-co-(hydroxyethyl acrylate)) (poly(NIPAM-co-HEA)) with molecular weights >106 g mol 1 are synthesized. The dendritic macromolecules display molecular weight distributions Ɖ smaller than 1.36. The reaction cascade found is adjusted and extended in terms of polymerization control for the synthesis of thermo-responsive water soluble arborescent poly((ethylene glycole methyl ether acrylate)-stat-(hydroxyethyl acrylate)) (poly(EGMEA-stat-HEA)). The synthesis features (i) statistical copolymerization of comonomers, (ii) quantitative initiation efficiency, (iii) low Ɖ, and (iv) highest end-group functionality (EGF). The poly(EGMEA-stat-HEA) polymers are soluble in water cooled with an ice bath. The reaction scheme allows to control the distance between branches by stoichiometry of comonomers and the quantitative exchange of end-groups. Dissipative particle dynamics (DPD) simulations show the solution behavior of rigid spheres. At liquid/liquid interface and on mica surface arborescent poly(EGMEA-stat-HEA) display their flexible nature and spread to an almost 2D disc-like conformation with sub nanometer height (<1 nm) at solid/air interface. Additionally, lowering of the interfacial tension of the toluene/water interface is found to be independent of the polymer’s generation. Two different approaches towards double-hydrophilic arborescent copolymers are presented. One relying on the grafting-onto strategy. Poly(ethylene glycols) and polyacrylamides with thiol end-groups each are reacted with arborescent poly(EGMEA-stat-HEA) substrates in a thio-bromo substitution resulting in double-hydrophilic arborescent copolymers in an easy synthesis. The other strategy features grafting oligo(ethylene glycol) methyl ether acrylate (OEGMEA) from arborescent poly(EGMEA-stat-HEA) substrate yielding generation three poly(EGMEA-stat-HEA)-graft-poly(OEGMEA). These display disc-like conformations at the solid/air interface in atomic force microscopy (AFM) and reveal the branched architecture in both height and phase images.

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