Structure, dynamics and barrier performance relationship in furan-based polyesters

World plastic production has reached impressive values and is going to further increase in the coming years [1]. Indeed, plastics cover up to 50% of primary food packaging, thanks to their low price, lightness, easiness of production and processability, modulation of properties and durability. This massive consumption is accompanied by a consistent waste generation, mainly disposed in landfills [1], with very high carbon footprint. In order to reduce environmental impact, the use of bioplastics can be considered as a sustainable alternative to traditional fossil-based plastics. The great and growing interest in sustainability is so driving the development of biobased materials, i.e. obtainable from renewable sources, which could be or not biodegradable and that are characterized by minimum waste production, transport efficiency and controlled after-use disposal and/or recycling, being this last considered by European Commission the best option [2]. In the particular case of food packaging application, high barrier properties and proper mechanical response are fundamental requisites, and not many biopolymers could be employed for this scope. Conversely, the most used commercial products are multilayer and formed by different materials, preventing thus the recycling of the product. In this context, polyesters synthesized from 2,5-furan dicarboxylic acid can be considered very interesting candidates since combine biobased nature with outstanding barrier properties and very good mechanical behavior. Such characteristics render them particularly promising as monomaterials for food packaging applications, in view of their possible recycling. In the present work, poly(pentamethylene furanoate) PPeF (Figure 1) a new furan-based polyester, has been synthesized and characterized. Despite being an amorphous and rubbery polymer at room temperature, PPeF can be processed in form of film. This last shows exceptional barrier and mechanical response in view of an application in flexible food packaging. With the aim of shedding light on the origin of solid-state properties of this polymer, a study combining calorimetric, diffractometric and spectroscopic techniques has been carried out.