Poly(meth)acrylamides are highly interesting polymers that re more hydrophilic than the corresponding poly(meth)acrylates due to the presence of the amide groups. Hence, various hydrophilic poly(meth)acyrlamides are commonly used as (responsive) biomaterials, including poly(N-2-hydroxypropylmethacrylamide) and poly(N-isopropylacrylamide).

The amidation of polymers with non-activated ester side chains provides potential for creating higher added value poly(meth)acrylamide materials through the introduction of more complex amide side-chains,¹ which would be much more expensive, complicated and sometimes even impossible through direct polymerization of the corresponding monomers. However, despite that polymers with methyl ester side chains, such as poly(methyl acrylate) and poly(methyl methacrylate) (PMMA) are widely available, the non-activated side chain ester groups have low reactivity for transesterification or amidation.

In this lecture, the recent progress from our group in this area will be discussed. First of all, we developed a 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) catalyzed procedure allowing efficient full or partial amidation of the side chains of poly(methyl acrylate), allowing accurate control over the introduction of functional side chains, such as allyl or cyclohexenyl groups that allowed crosslinking into polymer networks.² Moreover, we discovered that the amidation is strongly accelerated when a secondary hydrogen bond donating or accepting group is present on the utilized primary amine-containing reagent.³ Furthermore, efficient introduction of secondary amine groups will be discussed through amidation with N-ethyl-ethylenediamine, whereby selective amidation of the primary amine occurred.⁴

These results from our group provide a sound basis for future development of functional polyacrylamide based materials through amidation of poly(methyl acrylate) and also provide a first step towards future development of protocols for amidation and upcycling of the bulk polymer PMMA, as is ongoing in our laboratories. The amidation of PMMA is, however, much more challenging due to the enhanced sterical hindrance of the polymer backbone.

References:

1. J. F. R. Van Guyse, Y. Bernhard, A. Podevyn, R. Hoogenboom, Angew. Chem. Int. Ed. 2023, 62, e202303841.
2. J. F. R. Van Guyse, J. Verjans, S. Vandewalle, K. De Bruycker, F. E. Du Prez, R. Hoogenboom, Macromolecules 2019, 52, 5102-5109.
3. J. F. R. Van Guyse, M. N. Leiske, J. Verjans, Y. Bernhard, R. Hoogenboom, Angew. Chem. Int. Ed. 2022, 61, e202201781.
4. Y. Bernhard, J. F. R. Van Guyse, M. Purino, R. Hoogenboom, Eur. Polym. J. 2023, 192, 112077.