Free radical polymerization of dimethyl amino ethyl methacrylate initiated by poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) macroazo initiator: Thermal and physicochemical characterization

Authors: HAZER, BAKI - Bülent Ecevit University; TASCI, FULYA - Mehmet Akif Ersoy University; MODJINOU, TINA - University Of Paris; LANGLOIS, VALERIE - University Of Paris; Ashby, Richard - Rick

Submitted to: Journal of Polymers and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2023
Publication Date: 4/7/2023
Citation: Hazer, B., Tasci, F., Modjinou, T., Langlois, V., Ashby, R.D. 2023. Free radical polymerization of dimethyl amino ethyl methacrylate initiated by poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) macroazo initiator: Thermal and physicochemical characterization. Journal of Polymers and the Environment. https://doi.org/10.1007/s10924-023-02857-3.
DOI: https://doi.org/10.1007/s10924-023-02857-3

Interpretive Summary: Efforts to realize a more bio-based economy and to mitigate the plastic disposal problem, biodegradable plastic substitutes have been developed and are showing increased promise for wide-spread use. Polyesters derived from microbial sources have been a primary focus owing to their renewability, degradability, and their ability to reduce greenhouse gas emissions. Unfortunately, these microbial polyesters (typically referred to as polyhydroxyalkanoates (PHA) based on their chemical structure) can only be synthesized based on the genetic capability of the producing organism. As such, many of these microbial polyesters can benefit from chemical modification to improve their properties such that they can serve as bio-based substitutes for petroleum-based materials. In this study, a specific type of PHA biopolymer (poly-3-hydroxybutyrate-co-3-hydroxyhexanoate) was chemically modified to make it more reactive and then chemically combined with another functional chemical intermediate (dimethyl aminoethyl methacrylate) to produce a new bio-based polymer with both hydrophobic (water repelling) and hydrophilic (readily dissolves in water) chemical groups (amphiphile). This type of chemical reaction can be used to prepare many different types of copolymeric materials to obtain a very versatile range of PHA derivatives designed for a wide range of diverse applications.

Technical Abstract: A novel macro intermediate based on poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) was synthesized for use in the copolymerization with dimethyl amino ethyl methacrylate (DMAEMA). Methyl amino ethanol was reacted with PHBHHx to prepare a dihydroxy terminated polyester. The hydroxyl ends of the obtained PHBHHx derivatives were capped with 4,4’-azobis cyanopentanoic acid to obtain the PHBHHx macroazo initiator (PHBHHx-AI) for free radical copolymerization of DMAEMA at 70 degrees C. A smooth increase in DMAEMA units in the obtained block copolymer by the polymerization time was observed. The overall rate constants for free radical polymerization of DMAEMA initiated by PHBHHx-AI was k = 2.33x10-4 Lmol-1s-1. Block copolymers were characterized using the 1H NMR, FTIR, DSC and TGA techniques.