In the context of the defossilisation of the chemical industry, our team has been investigating the incorporation of monosaccharides into synthetic polymer backbones. The goal of this research is to create renewable materials with attractive sustainability attributes (e.g., degradability, chemical recyclability), and which are tuneable thanks to the functionalisation potential of sugar moieties.

This talk will present our recent work on the development of monomers from pentose sugars such as xylose, as well as from deoxyribonucleosides, and their polymerisation using techniques such as ring-opening co-polymerisation (ROCOP) [1], acyclic metathesis polymerisation (ADMET) [2], or thiol-ene polymerisation [3].
The derivatisation of xylose with potassium thiocyanate will also be introduced as a versatile synthetic handle to further fine-tune polymer properties [4].

Finally, some preliminary results on the applications of those synthetic carbohydrate polymers will be shown, including as solid polymer electrolytes, and pharmaceutical amorphous solid dispersions [5].

Polysaccharides are naturally occurring polymers with derivatives that are often both biodegradable and biocompatible. The pendant groups present, along with the general polymer architecture, strongly influence the properties of the polysaccharide, such that some polysaccharides are readily water-soluble (e.g. starch) whilst others are highly hydrophobic (e.g. chitin). With an increasing importance placed on utilising sustainable raw materials, polysaccharide-containing block copolymers have become a particular focus as renewable alternatives for surfactants, drug delivery vehicles and other applications.[1]
Due to the presence of the many pendant functional groups, polysaccharide-containing block copolymers are typically synthesised either by a “grafting to” or “grafting from” approach.[2] The preparation of linear block copolymers poses more challenges, as the reducing chain-end of a polysaccharide is largely inaccessible. Regioselective functionalisation is possible when the polysaccharide is in an open-chain aldehyde form, rather than a ring-closed hemiacetal, such that reactions like imine formation and reductive amination can occur. Reductive amination with harsh reducing agents has previously been used to synthesise amphiphilic block copolymers from hydrophilic polysaccharides such as xyloglucan and dextran, in combination with post-polymerisation coupling, click chemistry and/or reversible addition fragmentation chain transfer (RAFT) polymerisation.[3,4]
Here, a low molecular weight dextran (Mn ~ 6000) has been functionalised at the reducing chain-end, under mild reaction conditions. This modification of the polysaccharide enables the preparation of a macromolecular chain transfer agent (macroCTA) to facilitate chain extension via RAFT polymerisation.

Plastics are ubiquitous in society and have been posited as a key part of the green revolution due to their potential to replace metal components in certain industries.1 However, the persistence of plastics in the environment is a major problem. Recent legislation (such as EU fertilising products regulation 2019) requires a high degree of biodegradability from polymers used in certain sectors.2 It is therefore increasingly important to develop a holistic understanding of emerging polymers to better tailor them to different sectors.

Our group focuses on developing sustainable polymers, utilising sugars as a feedstock due to their cheap, abundant and highly functionalisable nature.3 The ring opening polymerisation of a xylose-derived oxetane monomer into a xylose-derived polyether was reported in 2021 with high thermal stability and crystallinity.3 Recently ring opening copolymerisation of the xylose-derived oxetane monomer with isothiocyanates and cyclic anhydrides has been reported with applications in metal adsorption and drug formulations.4, 5 This presentation will detail efforts to further the develop these polymers by improving their processability through block copolymerisation, increasing their functionality and testing degradability. Block copolymerisation with macroinitiators such as PEG has allowed access to polymers with high thermal degradability and film forming properties with improved mechanical performance over the initial polyether.

Climate change and population growth threaten global food security and water resources. Efficient solutions for sustainable water use in agriculture are essential. Hydrogels, which absorb and release water, are promising as soil conditioners to increase crop productivity [1]. In this work a novel method was developed to produce biodegradable cellulose hydrogels for agriculture by repurposing cellulose solvent salts as nitrogen fertilizers, which is an alternative to petroleum-based SAPs for agriculture applications.

Allylic cellulose derivatives were obtained by homogenous modification in NaOH/urea solvent system. The recyclability of the washing solvent used in synthesis (methyl ethyl ketone-MEK) was evaluated over five cycles. Resultant solutions were neutralized with nitric acid, resulting in sodium nitrate, as nitrogen-based fertilizer, which benefits from urea presence, the most used nitrogen fertilizer [2]. Hydrogels were prepared by UV-FRP, crosslinking allylic cellulose in the presence of salts. The influence of crosslinking density on hydrogel properties was studied. EDS analysis confirmed the distribution of nitrogen and sodium into cellulose structure (Fig.1-A). The hydrogels showed a 2500% swelling capacity, as well as pH and salt resistance. Fertilizers release in soil tests showed a delayed release compared to the salts’ diffusion (Fig.1-B). Biodegradability tests showed significant degradation within 30 days, with 40 wt.% remaining (Fig.1-C).

This environmentally sustainable approach aligns with sustainability goals and shows the potential of allylic cellulose derivatives for the development of eco-friendly hydrogels for an increasing range of applications [3]. Ongoing studies aim to improve hydrogels properties by incorporating additional polymers into the hydrogel network.

Biobased copoly(ester amide)s of 2,5-furandicarboxylic acid (Figure 1) were synthesized and processed into films to test their suitability for food packaging application (1).
Polymer films were subjected to WAXS, DSC, SEM and water contact angle analyses. Functional properties (such as mechanical response and gas permeability) and biodegradation mechanism and rate were studied and correlated with chemical structure and composition.
The prepared films were also treated with food simulants.
The experimental results show copolymerization: i) improves mechanical resistance to deformation and elongation at break (up to 600%); ii) decreases oxygen transmission rate under different temperatures and humidity degrees, being comparable to those of commercial PET and polyamides in mild conditions (23 °C, 0% RH) and keeping better than commercial polyolefins in tropical conditions and after aggressive treatment with food simulants.
The experimental results also show it is possible to tune the degradation pathway, and the corresponding rate, by properly varying composition: higher percentages of amido groups enhance biodegradation via bulk hydrolysis mechanism (even if there is the preferential cleavage of ester bonds), while low percentages increase surface erosion as the main mechanism of degradation.
The combination of the excellent mechanical and gas barrier properties, and their resistance to humid conditions show that copoly(ester amide)s could be eligible for the production of monolayer food packaging, for the protection of oxidation-sensitive food products rather than carbonated beverages, substituting multilayer polymeric systems which are challenging to recycle.

Polymers are the material of choice in packaging applications due to their light weight, low cost and high performance. They are used for a short period of time and afterwards they are disposed. Since they are not designed for recyclability or degradability, they contribute to the problem of plastic waste accumulating in the environment. Great efforts have been done to develop biodegradable and/or recyclable polymers. However, their physical performance, including the thermal stability, mechanical and transport properties are not comparable to the polymers employed nowadays in the market which prevents their use in the packaging sector.
Taking into account these issues in this work we develop a new sustainable polymer system that can be obtained from renewable resources with outstanding mechanical and barrier properties. Those properties are comparable to petroleum based and non-recyclable polymers and are better than biodegradable polymers.