Synthesis of Polymers From Bio‐Based Methacrylates Comprising Aromatic or Aliphatic Structures Using NIR‐Mediated ATRP

NIR-mediated ATRP is used for the synthesis of polymethacrylates from the bio-based monomers 4-(4-methacryloyloxyphenyl)butan-2-one and methyl 9-hydroxy-10-(methacryloyloxy) octadecanoate / methyl 9-(methacryloyloxy)-10-hydroxy octadecanoate. According to the NIR-mediated ATRP protocol, excitation is carried out at 790 nm in the presence of copper(II)bromide tris(2-pyridylmethyl)amine complex as deactivator and a heptamethine cyanine comprising a barbiturate group in the meso-position operating as sensitizer. The homopolymers obtained are compared with similarly made poly(methyl methacrylate) regarding yield, molecular weight, dispersity, and glass transition temperature. Furthermore, block copolymers made from methyl methacrylate and the bio-based monomers are included in this comparison. Dispersity is broader in the case of the bio-based polymethacrylates compared to poly(methyl methacrylate), indicating a higher contribution of chain termination during NIR-mediated ATRP using the bio-based methacrylates. Notably, all macroinitiators are chain extendable. In addition, the block copolymers synthesized from the bio-based methacrylates significantly differ regarding their solubility, that is caused by the distinct structural features in the ester part of these monomers. Results obtained from GPC investigation of tetrahydrofuran soluble copolymers are included in the discussion. These results show that the initiation efficiency is lower for the methyl 9-hydroxy-10-(methacryloyloxy) octadecanoate / methyl 9-(methacryloyloxy)-10-hydroxy octadecanoate isomer mixture compared to methyl methacrylate.