Metal-free synthesis of novel biobased dihydroxyl-terminated aliphatic polyesters as building blocks for thermoplastic polyurethanes

Investigations into the characterization, degradation, and applications of biodegradable polymers by mass spectrometry

Biodegradable polymers have been getting more and more attention because of their contribution to the plastic pollution environmental issues and to move towards a circular economy. Nevertheless, biodegradable materials still exhibit various disadvantages restraining a widespread use in the market. Therefore, additional research efforts are required to improve their performance. Mass spectrometry (MS) affords a relevant contribution to optimize biodegradable polymer synthesis, to confirm macromolecular structures, to examine along the time the progress of degradation processes and highlight advantages and drawbacks in the extensive applications. This review aims to provide an overview of the MS investigations carried out to support the synthesis of biodegradable polymers, with helpful information on undesirable products or polymerization mechanism, to understand deterioration pathways by the structure of degradation products and to follow drug release and pharmacokinetic. Additionally, it summarizes MS studies addressed on environmental and health issues related to the extensive use of plastic materials, that is, potential migration of additives or microplastics identification and quantification. The paper is focused on the most significant studies relating to synthetic and microbial biodegradable polymers published in the last 15 years, not including agro-polymers such as proteins and polysaccharides.

Flexible biomimetic block copolymer composite for temperature and long-wave infrared sensing

Biological compounds often provide clues to advance material designs. Replicating their molecular structure and functional motifs in artificial materials offers a blueprint for unprecedented functionalities. Here, we report a flexible biomimetic thermal sensing (BTS) polymer that is designed to emulate the ion transport dynamics of a plant cell wall component, pectin. Using a simple yet versatile synthetic procedure, we engineer the physicochemical properties of the polymer by inserting elastic fragments in a block copolymer architecture, making it flexible and stretchable. The thermal response of our flexible polymer outperforms current state-of-the-art temperature sensing materials, including vanadium oxide, by up to two orders of magnitude. Thermal sensors fabricated from these composites exhibit a sensitivity that exceeds 10 mK and operate stably between 15° and 55°C, even under repeated mechanical deformations. We demonstrate the use of our flexible BTS polymer in two-dimensional arrays for spatiotemporal temperature mapping and broadband infrared photodetection.

Biodegradable Polyester Synthesis in Renewed Aqueous Polycondensation Media: The Core of the New Greener Polymer-5B Technology

An innovative enzymatic polycondensation of dicarboxylic acids and dialcohols in aqueous polymerization media using free and immobilized lipases was developed. Various parameters (type of lipases, temperature, pH, stirring type and rate, and monomer carbon chain length) of the polycondensation in an oil-in-water (o/w) miniemulsion (>80% in water) were evaluated. The best results for polycondensation were achieved with an equimolar monomer concentration (0.5 M) of octanedioic acid and 1,8-octanediol in the miniemulsion and water, both at initial pH 5.0 with immobilized Pseudozyma antarctica lipase B (PBLI). The synthesized poly(octamethylene suberate) (POS) in the miniemulsion is characterized by a molecular weight of 7800 g mol−1 and a conversion of 98% at 45 °C after 48 h of polycondensation in batch operation mode. A comparative study of polycondensation using different operation modes (batch and fed-batch), stirring type, and biocatalyst reutilization in the miniemulsion, water, and an organic solvent (cyclohexane:tetrahydrofuran 5:1 v/v) was performed. Regarding the polymer molecular weight and conversion (%), batch operation mode was more appropriate for the synthesis of POS in the miniemulsion and water, and fed-batch operation mode showed better results for polycondensation in the organic solvent. The miniemulsion and water used as polymerization media showed promising potential for enzymatic polycondensation since they presented no enzyme inhibition for high monomer concentrations and excellent POS synthesis reproducibility. The PBLI biocatalyst presented high reutilization capability over seven cycles (conversion > 90%) and high stability equivalent to 72 h at 60 °C on polycondensation in the miniemulsion and water. The benefits of polycondensation in aqueous media using an o/w miniemulsion or water are the origin of the new concept strategy of the green process with a green product that constitutes the core of the new greener polymer-5B technology.

Copolymerization of Natural Camphor-Derived Rigid Diol with Various Dicarboxylic Acids: Access to Biobased Polyesters with Various Properties

In this work, alicyclic (1R,3S)-1,2,2-trimethylcyclopentane-1,3-dimethanol (TCDM), derived from natural camphor, was copolymerized with linear α,ω-diacids, terephthalic acid (TPA), and 2,5-furandicarboxylic acid (FDCA), affording a series of polyesters with functional properties. 2D NMR spectroscopy revealed that the stereoconfiguration of TCDM was preserved after polymerization. The TCDM polyester based on TPA showed high thermostability, high T_g value (115 °C), high modulus (1.3 GPa), and high ultimate strength (29.8 MPa). The TCDM polyester based on 1,4-succinic acid exhibited excellent ductility and resilience. Lastly, the rigidity analysis based on van Krevelen's group contribution method, coupled with the comparisons between TCDM- and sugar-based polyesters, confirmed that TCDM is a highly reactive and rigid diol. Results indicate that TCDM polyesters are suitable for a wide range of applications, including hot-filled containers and transparent packaging materials. This work addresses some critical needs for high performance biopolymers such as achieving high T_g values, high thermostability, and high transparency.

Mass Spectrometry of Polyurethanes

This review covers the applications of mass spectrometry (MS) and its hyphenated techniques to characterize polyurethane (PU) synthetic polymers and their respective hard and soft segments. PUs are commonly composed of hard segments including methylene bisphenyl diisocyanate (MDI) and toluene diisocyanate (TDI), and soft segments including polyester and polyether polyols. This literature review highlights MS techniques such as electrospray ionization (ESI), matrix assisted laser/desorption ionization (MALDI), ion mobility-mass spectrometry (IM-MS), and computational methods that have been used for the characterization of this polymer system. Here we review specific case studies where MS techniques have elucidated unique features pertaining to the makeup and structural integrity of complex PU materials and PU precursors.

Reducing off-Flavour in Commercially Available Polyhydroxyalkanoate Materials by Autooxidation through Compounding with Organoclays

Polyhydroxyalkanoates (PHAs) are nowadays considered competent candidates to replace traditional plastics in several market sectors. However, commercial PHA materials exhibit unsatisfactory smells that can negatively affect the quality of the final product. The cause of this typical rancid odour is attributed to oxidized cell membrane glycolipids, coming from Gram-negative production strains, which remain frequently attached to PHAs granules after the extraction stage. The aim of this research is the development of customised PHA bio-nano-composites for industrial applications containing organomodified nanoclays with high adsorbance properties able to capture volatile compounds responsible for the displeasing fragrance. To this end, a methodology for the detection and identification of the key volatiles released due to oxidative degradation of PHAs has been established using a headspace solid-phase microextraction technique. We report the development of nine bio-nano-composite materials based on three types of commercial PHA matrices loaded with three species of nanoclays which represent a different polar behaviour. It has been demonstrated that although the reached outcoming effect depends on the volatile nature, natural sepiolite might result in the most versatile candidate for any the PHA matrices selected.

Green and selective polycondensation methods toward linear sorbitol-based polyesters: enzymatic versus organic and metal-based catalysis

Renewable polyesters derived from a sugar alcohol (i.e., sorbitol) were synthesized by solvent-free polycondensation. The aim was to prepare linear polyesters with pendant hydroxyl groups along the polymer backbone. The performance of the sustainable biocatalyst SPRIN liposorb CALB [an immobilized form of Candida antarctica lipase B (CALB); SPRIN technologies] and the organo-base catalyst 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD) were compared with two metal-based catalysts: dibutyl tin oxide (DBTO) and scandium trifluoromethanesulfonate [also known as scandium triflate, Sc(OTf)3 ]. For the four catalytic systems, the efficiency and selectivity for the incorporation of sorbitol were studied, mainly using (13) C and (31) P NMR spectroscopies, whereas side reactions, such as ether formation and dehydration of sorbitol, were evaluated using MALDI-TOF-MS. Especially the biocatalyst SPRIN liposorb CALB succeeded in incorporating sorbitol in a selective way without side reactions, leading to close-to-linear polyesters. By using a renewable hydroxyl-reactive curing agent based on l-lysine, transparent and glossy poly(ester urethane) networks were successfully synthesized offering a tangible example of bio-based coatings.