Grafting 1-dodecene onto inherently isotactic biologically-derived poly(3-hydroxybutyrate) to induce tacticity change

Biologically-derived, perfectly isotactic poly(3-hydroxybutyrate) (P[(R)-3HB]) is a biodegradable polymer with properties that make it a promising biodegradable substitute for petroleum-based plastics. However, its inherent brittleness and narrow thermal processing window still constrain its potential applications. To address this, we attempt the first deliberate modification of the tacticity of this material, representing a paradigm shift in the conceptual framework of strategies to broaden the industrial applications of commercially available P[(R)-3HB]. Tacticity modification was achieved through peroxide-based alkene (1-dodecene) grafting. Extensive nuclear magnetic resonance (NMR) spectroscopy, including ¹H NMR, HMBC NMR, HSQC NMR, 2D DOSY NMR, and proton decoupled ¹³C NMR were conducted to confirm and quantify alkene grafting and the subsequent disruption in tacticity based on the portion of atactic diads/triads formed. It was found that, at grafting levels of up to 9.6 mol% of monomer units, an atactic portion of up to 1.9 % was achieved. The melting temperature of the resulting P3HB materials dropped by 30 °C compared to P[(R)-3HB], likely as a result of the side-chain disrupting crystallinity. This work is the first to demonstrate that deliberate tacticity modification of commercially available P[(R)-3HB] through solvent-based alkene grafting is practically achievable.