Exploring different thermoplastics from lignocellulosic building blocks and monomers

The need to replace conventional fossil-based plastics is becoming more imperative. As climate change is more visibly affecting our society, employing non-sustainable resources to produce plastics is aggravating the problem. Moreover, these long-lasting, non-recycled wastes end up in our oceans, creating an intrinsic environmental pollution problem. Researching new biobased building blocks to enable the production of plastics with better properties than conventional plastics has been a long and evolving process. Such bioadvantage strategy usually f ocuses on designing rigid monomers to
improve the thermal and mechanical properties of the polymers. Another possibility is to introduce polar functions to obtain better physical properties. This thesis focuses on the design of several new lignocellulosic monomers and building blocks to produce thermoplastics. The two strategies mentioned (rigidity and polarity) were explored and are reported here.
In Paper I, isosorbide-based methacrylate monomers with varying pendant alkanoyl chains were synthesized, and subsequently polymerized. The resulting polymers showed thermal properties depending on the length of the pendant alkanoyl chain. Shorter chains yielded amorphous materials,
while longer chains af f orded semi-crystalline polymers, even showing liquid crystalline behavior in some cases. In Paper II, a rigid spirocyclic diol derived from citric acid was synthesized and used to produce polycarbonates of different molecular weights. The thermal properties of the higher molecular
weight were significantly better. In Paper III, the spirocyclic diol from Paper II was, alongside two other spirocyclic diols derived from citric acid, (meth)acrylated to obtain rigid di(meth)acrylate monomers of different structures. These monomers were polymerized by thiol-Michael polymerization with dithiols of various rigidity, affording a library of polymers. Their thermal properties were successfully correlated to their chemical structure. Additionally, the ketals units were successfully cleaved in a mixture of aqueous acid and acetone, opening the way for potential chemical recycling. In Paper IV, besides using rigid structures, polar groups such as nitrile functions were introduced in lignin-inspired polymers, leading to polymers and copolymers with improved thermal properties, as well as solvent resistance. In Paper V, using a similar strategy, a bis-vanillin monomer containing nitrile functions was employed to produce polyesters with improved thermal properties.