New Polymers from Biomass-Derived Hydroxycinnamic Acid Derivatives

Polymers play a central role in shaping our world across various fields, but their heavy reliance on petrochemicals poses climate change, environmental and health risks. To address and alleviate these issues, transitioning to sustainable polymers, sourced from renewable materials such as lignocellulosic biomass, is crucial. Over 100 million tons of lignin is generated annually from the pulp and paper industry, often incinerated as waste. This leads to a growing interest within research communities to explore the valorization of lignin. One promising approach involves depolymerization of lignin under various conditions to produce valuable aromatic building blocks. Apart from lignin, hemicellulose, vegetable oils and fruits serve as another valuable biological sources for different building blocks. Among these building blocks, hydroxycinnamic acid derivatives are particularly interesting, primarily because of their accessibility from a variety of biological sources. The focus of this Thesis is to exploit the chemistry of hydroxycinnamic acid derivatives for the synthesis of different classes of polymers.In Chapter 1, an in-depth overview is provided that discusses the varied biological sources of hydroxycinnamic acid derivatives, including lignin, hemicellulose, and vegetable oils. This chapter details the incorporation of these fundamental building blocks within biopolymers and provides a comprehensive overview of their isolation processes. Furthermore, a systematic review of the existing literature is presented with a nuanced understanding of the diverse polymers derived from hydroxycinnamic acids.Chapter 2 explores the synthesis of a novel poly(ether carbonate) from hydroxycinnamic acid derivatives. Hydroxycinnamic acid derivatives will be used to generate symmetric diols, which serve as monomers for the synthesis of diverse poly(ether carbonate)s. The resulting polymers undergo successful depolymerization using protic salts, demonstrating the viability of a chemical recycling method. This process of polymerization and depolymerization is executed for four cycles, showcasing the robustness of the chemical recycling approach.Chapter 3 investigates the synthesis of a series of new class of poly(ether ester urea)s. The monomers used in this part are prepared from the symmetric diols obtained in Chapter 2, which are converted into diamines, which are used for the synthesis of poly(ether ester urea)s. Unlike the traditional synthesis of poly(ester urea)s, which typically involves the use of toxic reagents such as triphosgene derivatives, our approach utilized the environmentally friendly carbonate source, dimethyl carbonate. The impact of various parameters was systematically investigated including temperature, catalyst and reaction time on molecular weight. While optimized conditions demonstrate successful polymer production of these polymers, further refinement is essential for achieving higher molecular weight polymers.In Chapter 4, the synthesis of poly(ether carbonate)s using biomass-derived diester derivatives and biobased 1,6-hexanediol is reported. The chemical recycling of the resulting polymers is explored. The chemically recycled diester derivatives were investigated into two different ways: firstly, these building blocks were repolymerized under the same polymerization conditions; secondly, the diester derivatives were reduced to diols, which are then utilized for synthesizing another class of poly(ether ester)s.