Fiona Louise Hatton

Maiyong Zhu, Gerard Lligadas, Fiona L. Hatton, Garret Miyake and Antoine Buchard introduce the Green Chemistry , Polymer Chemistry and RSC Sustainability themed collection ‘Make polymers sustainable, why and how?’.

The increasing utilization of single-use plastics in the food sector poses serious environmental challenges. A circular economy approach, i.e., reusing packaging before recycling, offers a promising solution but raises concerns about cross-contamination between food products. This study investigates how repeated use and cleaning affect the surface topography of plastic food packaging and, in turn, how these changes influence cleaning efficiency and assessment. Recycled polyethylene terephthalate (rPET) trays were subjected to 20 industrial wash cycles with and without detergent concentration of 0.3% v/v at the following temperatures: 55 °C wash, 70 °C rinse. Surface roughness was measured using mechanical and optical techniques. Additionally, trays were roughened with sandpaper of varying grit sizes to simulate mechanical wear during consumer use. Cleanability was assessed using UV fluorescence imaging and adenosine triphosphate (ATP) assays. Results showed no significant increase in surface roughness after 20 wash cycles. However, artificially roughened surfaces retained more food residue, complicating cleaning. The application of UV fluorescence imaging proved more effective than ATP assays in detecting food residues on textured surfaces. These findings support the use of advanced imaging for evaluating the hygiene of reusable packaging and highlight key considerations for implementing circular reuse systems in food packaging.

The positive temperature coefficient (PTC) effect observed in conductive polymer composites (CPCs) holds significant promise due to its wide materials selection and ability to offer enhanced sensitivity. However, traditional CPCs have relatively high PTC switching temperatures (typically above 100 °C) and are often unsuitable for bodily healthcare devices. This study introduces a novel approach leveraging the synergistic effect of an eco‐friendly fatty acid, namely lauric acid (LA), with flexible styrene‐ethylene‐butylene‐styrene (SEBS) thermoplastic elastomer (TPE) as a matrix and graphene nanoplatelets (GNPs) as a conductive filler. The composite film demonstrates exceptional temperature responsiveness at body‐relevant temperatures (35–40 °C) with a PTC intensity reaching an unprecedented 4 orders of magnitude, set apart by its fine‐tuning ability across a remarkable detecting temperature interval (Maximum temperature coefficient of resistance (TCR): 471.4% °C⁻¹). This advancement is facilitated through a carefully engineered morphology, wherein the distribution of LA significantly influences the conductive network's reformation within the composite, with the in‐situ optical microscope used to reveal the reformation of the conductive network structure. The flexible composite demonstrates significant potential for body temperature sensing, self‐regulating heating, and passive cooling, paving the way for future developments in eco‐friendly, highly sensitive, and flexible sensors in wearable health monitoring and thermotherapy.

Polymeric materials based on fatty acids (FAs) have a combination of characteristics (alkene groups, hydrophobicity, tuneable T_g) that give them great potential as renewable, high value materials. Here, we investigate the base catalysed transesterification of four different plant oils (high oleic sunflower, olive, hydrogenated coconut and hydrogenated rapeseed) with N-hydroxyethyl acrylamide. By conducting kinetics experiments, investigating potential side reactions and improving isolation of the target products, we were able to identify reactive impurities (radical inhibitors, unintended co-monomers) that were found to remain in the impure brine washed plant oil-based monomers (POBM). Kinetics experiments were then performed to investigate the RAFT polymerisation of these monomers. It was found that the more sustainable brine washing process was viable for the controlled radical polymerisation of the higher k_{p app} (saturated) monomers, however column purification was necessary for good control of unsaturated monomers. Polymers with values of M_n between 3,000 and 12,000 gmol^-1 were synthesised and dependent on the FA source exhibited either amorphous or semi-crystalline behaviour (T_g values between -1 and 33 °C, T_m values between 48 and 66 °C). This work demonstrates the first example of RAFT polymerisation of acrylamide monomers derived from plant oils by a one step direct transesterifcation, opening the door for novel well-defined, functional bio-based polymers.

We report the RAFT solution polymerisation of bio-based monomer γ-methyl-α-methylene-γ-butyrolactone in DMSO and the more sustainable solvent Cyrene.

Size-dependent adsorption of Cu²⁺ ions onto polystyrene nanoparticles in aquatic environments: influence of UV-ageing, temperature and salt ions in the medium.

Essential oils have been identified as effective natural compounds to prevent bacterial infections and thus are widely proposed as bioactive agents for biomedical applications. Across the literature, various essential oils have been incorporated into electrospun fibres to produce materials with, among others, antibacterial, anti-inflammatory and antioxidant activity. However, limited research has been conducted so far on the effect of these chemical products on the physical characteristics of the resulting composite fibres for extended periods of time. Within this work, electrospun fibres of poly(lactic acid) (PLA) were loaded with the essential oil limonene, and the impact of storage conditions and duration (up to 12 weeks) on the thermal degradation, glass transition temperature and mechanical response of the fibrous mats were investigated. It was found that the concentration of the encapsulated limonene changed over time and thus the properties of the PLA–limonene fibres evolved, particularly in the first two weeks of storage (independently from storage conditions). The amount of limonene retained within the fibres, even 4 weeks after fibre generation, was effective to successfully inhibit the growth of model microorganisms Escherichia coli, Staphylococcus aureus and Bacillus subtilis. The results of this work demonstrate the importance of evaluating physical properties during the ageing of electrospun fibres encapsulating essential oils, in order to predict performance modification when the composite fibres are used as constituents of medical devices.

The agri-food supply chain uses plastic food packaging alongside many other types of packaging materials

This work demonstrates for the first-time biobased, temperature-responsive diblock copolymer nanoparticles synthesized by reversible addition-fragmentation chain-transfer (RAFT) aqueous emulsion polymerization-induced self-assembly (PISA). Here, monomers derived from green solvents of the lactic acid portfolio, N,N-dimethyl lactamide acrylate (DMLA) and ethyl lactate acrylate (ELA), were used. First, DMLA was polymerized by RAFT aqueous solution polymerization to produce a hydrophilic PDMLA macromolecular chain transfer agent (macro-CTA), which was chain extended with ELA in water to form amphiphilic PDMLA-b-PELA diblock copolymer nanoparticles by RAFT aqueous emulsion polymerization. PDMLA_x homopolymers were synthesized targeting degrees of polymerization, DP_x from 25 to 400, with relatively narrow molecular weight dispersities (Đ < 1.30). The PDMLA₆₄-b-PELA_y diblock copolymers (DP_y = 10-400) achieved dispersities, Đ, between 1.18 and 1.54 with two distinct glass transition temperatures (T_g) identified by differential scanning calorimetry (DSC). T_g(1) (7.4 to 15.7 °C) representative of PELA and T_g(2) (69.1 to 79.7 °C) of PDMLA. Dynamic light scattering (DLS) studies gave particle z-average diameters between 11 and 74 nm (PDI = 0.04 to 0.20). Atomic force microscopy (AFM) showed evidence of spherical particles when dispersions were dried at ∼5 °C and film formation when dried at room temperature. Many of these polymers exhibited a reversible lower critical solution temperature (LCST) in water with a concomitant increase in z-average diameter for the PDMLA-b-PELA diblock copolymer nanoparticles.

Single use plastic packaging and its environmental impacts have received much attention over the last few years from governments, businesses and consumers. One option to reduce plastic packaging waste and its associated environmental impacts is to shift towards circular business models, supplying reusable packaging options that are used many times before being recycled. One technical barrier to the implementation of plastic food packaging reuse is the need to effectively clean the packs and provide cleaning assurance to prevent the possibility of product crossover. This research investigated the feasibility of using Ultraviolet Fluorescence imaging to optically detect residual food fouling and thus assuring cleanliness in the case example of margarine spread tubs. Processing of obtained images was carried out using MATLAB® applying Otsu’s thresholding method. It was established that for the current setup the minimum detectable quantity of fouling was of the order 10^–4 g/mm². The assessment process was correlated against that of Adenosine Triphosphate assay, an industry-standard process for assessing the cleanliness of food contact surfaces. The implications of the investigated technique overcome one barrier to plastic food packaging reuse on an industrial scale. Fast and reliable fouling evaluation of every pack will underpin business and consumer trust in such a circular material flow. The established technique has the potential to form part of the wider reuse system for polymer packaging. Implications on optical detection optimization, packaging design, and suitability for automation are discussed alongside wider food supply chain considerations.