Photocrosslinkable Star Polymers via RAFT-Copolymerizations with N-Ethylacrylate-3,4-dimethylmaleimide

Abstract

This paper describes the Z-RAFT-star copolymerization of n-butyl acrylate (BA) and N-isopropyl acrylamide (NIPAm), respectively, with N-ethylacrylate-3,4-dimethylmaleimide (1.1), a monomer carrying a UV-reactive unit that undergoes photocrosslinking. Addition of 1.1 slows down the polymerization rate both for BA and for NIPAm polymerization. Double star formation due to radical attack to the 3,4-dimethylmaleimide moiety was found in the case of BA. Dead polymer formation, presumably due to aminolysis as side-reaction, was pronounced in the NIPAm system. These two effects broadened the molar mass distributions, but did not impede the formation of functional star polymers. The composition of the copolymers as well as the reactivity ratios for the applied comonomers were determined via NMR spectroscopy (BA-co-1.1 r 1.1 = 2.24 r BA = 0.95; NIPAm-co-1.1 r 1.1 = 0.96 r NIPAm = 0.05). In both cases, the comonomer is consumed preferably in the beginning of the polymerization, thus forming gradient copolymer stars with the UV-reactive units being located in the outer sphere.

Tailoring Confinement: Nano-Carrier Synthesis via Z-RAFT Star Polymerization

“…To this end, we developed and carefully explored the synthesis of star polymers from Z-RAFT star polymerization carrying cross-linkable DMI groups in an earlier publication entitled "Photocrosslinkable Star Polymers via RAFT-Copolymerizations with N-Ethylacrylate-3,4-dimethylmaleimide" [42]. In addition to kinetic findings-which are not relevant here-the following key outcomes from this earlier study are essential for the present work:…”

“…The next step of the nano-carrier synthesis according to Figure 2 is the generation of the diblock copolymer star using the previously synthesized polymers as macroRAFT agents [42]. The final carrier should be amphiphilic, therefore, the second block's hydrophilicity has to be contrary to the first block.…”

“…DMI-based monomers-as also thoroughly investigated by Kuckling et al [29,[39][40][41]-were employed in the present study: For the shell formation of the star polymers N-ethylacrylate-3,4-dimethylmaleimide (1.1) (see Figure 3) was used in this project as the cross-linkable comonomer. In a recent publication, which presented preliminary research to this present paper, we carefully investigated the Z-RAFT-star copolymerization of n-butyl acrylate (BA) and N-isopropyl acrylamide (NIPAam), respectively, with 1.1 [42]. It was found that addition of 1.1 slows down the polymerization rate both for BA and for NIPAm polymerization.…”

Let There Be Light: Photo‐Cross‐Linked Block Copolymer Nanoparticles

“…To fully realize the potential of photo‐cross‐linkable polymeric nanomaterials, it is advantageous to develop new routes to well‐defined block copolymers capable of controlled self‐assembly. In this manner, various nanosized morphologies can be obtained by supramolecular self‐assembly of individual components in solution and subsequent covalent “locking” by light‐induced stabilization …”

“…In this manner, various nanosized morphologies can be obtained by supramolecular self-assembly of individual components in solution and subsequent covalent "locking" by light-induced stabilization. [ 32,44 ] We have an interest in the preparation of well-defi ned core-shell nanoparticles by cross-linking of a single reactive block in AB diblock copolymers. [45][46][47] Herein, we expand on that interest by focusing on block copolymers that can be induced to form well-defi ned nanoparticles by irradiation with light.…”