# Red-Light-Induced PET-RAFT Polymerization to Afford (Meth)acrylamide-Based Poly(N‑oxide) and Other Hydrophilic Polymers Featuring Neutral, Cationic, and Zwitterionic Groups as Solubilizing Side Chains

## TL;DR

This paper introduces a new light-based method to create specific water-loving polymers with potential uses in medicine.

## Contribution

A novel visible-light-induced PET-RAFT polymerization method for synthesizing (meth)acrylamide-based poly(N-oxide) polymers with high control and oxygen tolerance.

## Key findings

- The method produces polymers with narrow molecular weight distributions and high end-group fidelity.
- The polymerization is effective under oxygen and at various scales without losing control.
- The approach works for other hydrophilic monomers with neutral, zwitterionic, and cationic side chains.

## Abstract

Amine-oxide-containing polymers, poly­(N-oxide),
have emerged as an alternative to poly­(ethylene glycol) (PEG) for
imparting biofouling resistance and enabling drug delivery applications.
Poly­(N-oxide) can be obtained by thermally initiated
controlled free radical polymerization and postpolymerization modification
of the corresponding tertiary amine-containing polymers. However,
unexpected side reactions between (meth)­acrylamide-based N-oxide monomers and chain transfer agents commonly used in thermally
initiated reversible addition–fragmentation chain transfer
(RAFT) polymerization present challenges for achieving controlled
polymerization. Herein, this study exploits visible-light-induced
photoelectron transfer (PET)-RAFT polymerization of N-oxide-containing (meth)­acrylamides by using two types of zinc­(II)
porphyrin derivatives. This approach affords well-defined (meth)­acrylamide-
and methacrylate-based N-oxide polymers with narrow
molecular weight distributions even at a catalyst loading of less
than 100 ppm. Successful one-pot chain- extension experiments confirm
the good end-group fidelity. The optimized reaction condition can
afford well-defined polymers with M
n up
to 126 kDa. This method enables polymerization under complete oxygen
tolerance, with excellent temporal control and the ability to conduct
polymerization from low volume to large scale without diminishing
the control over polymerization. In addition, such a method is also
applicable to other hydrophilic methacrylate monomers featuring neutral
oligo­(ethylene glycol), zwitterionic sulfobetaine, and phosphocholine,
as well as cationic quaternary ammonium groups as side chains.