Eugenol: A Promising Building Block for Synthesis of Radically Polymerizable Monomers

Eugenol, a natural phenol currently mainly obtained from clove oil, is an interesting aromatic building block for the synthesis of novel biobased monomers. It can also be obtained from lignin depolymerization, becoming a promising building block due to lignin availability as biomass feedstock. The synthesis of eight monomers derived from eugenol containing polymerizable functional groups is achieved. The (meth)acrylation of eugenol, isoeugenol, and dihydroeugenol is performed and the solution homopolymerization of these biobased monomers is studied. Moreover, aiming to prepare functional polymers, the introduction of epoxy and cyclic carbonate groups is executed via modification of the allylic double bond present in eugenol derived methacrylate. Thus, a novel platform of versatile biobased monomers derived from eugenol is presented, opening the opportunity to use them in a wide range of polymerization processes and applications

Photoinduced polymerization of eugenol-derived methacrylates

Biobased monomers have been used to replace their petroleum counterparts in the synthesis of polymers that are aimed at different applications. However, environmentally friendly polymerization processes are also essential to guarantee greener materials. Thus, photoinduced polymerization, which is low-energy consuming and solvent-free, rises as a suitable option. In this work, eugenol-, isoeugenol-, and dihydroeugenol-derived methacrylates are employed in radical photopolymerization to produce biobased polymers. The polymerization is monitored in the absence and presence of a photoinitiator and under air or protected from air, using Real-Time Fourier Transform Infrared Spectroscopy. The polymerization rate of the methacrylate double bonds was affected by the presence and reactivity of the allyl and propenyl groups in the eugenol- and isoeugenol-derived methacrylates, respectively. These groups are involved in radical addition, degradative chain transfer, and termination reactions, yielding crosslinked polymers. The materials, in the form of films, are characterized by differential scanning calorimetry, thermogravimetric, and contact angle analyses

Smart soils track the formation of pH gradients across the rhizosphere

Aims Our understanding of the rhizosphere is limited by the lack of techniques for in situ live microscopy. Current techniques are either destructive or unsuitable for observing chemical changes within the pore space. To address this limitation, we have developed artificial substrates, termed smart soils, that enable the acquisition and 3D reconstruction of chemical sensors attached to soil particles. Methods The transparency of smart soils was achieved using polymer particles with refractive index matching that of water. The surface of the particles was modified both to retain water and act as a local sensor to report on pore space pH via fluorescence emissions. Multispectral signals were acquired from the particles using a light sheet microscope, and machine learning algorithms predicted the changes and spatial distribution in pH at the surface of the smart soil particles. Results The technique was able to predict pH live and in situ within ± 0.5 units of the true pH value. pH distribution could be reconstructed across a volume of several cubic centimetres around plant roots at 10 μm resolution. Using smart soils of different composition, we revealed how root exudation and pore structure create variability in chemical properties. Conclusion Smart soils captured the pH gradients forming around a growing plant root. Future developments of the technology could include the fine tuning of soil physicochemical properties, the addition of chemical sensors and improved data processing. Hence, this technology could play a critical role in advancing our understanding of complex rhizosphere processes

Zwitterionic Poly(amino acid methacrylate) Brushes

A new cysteine-based methacrylic monomer (CysMA) was conveniently synthesized via selective thia-Michael addition of a commercially available methacrylate-acrylate precursor in aqueous solution without recourse to protecting group chemistry. Poly(cysteine methacrylate) (PCysMA) brushes were grown from the surface of silicon wafers by atom-transfer radical polymerization. Brush thicknesses of ca. 27 nm were achieved within 270 min at 20 °C. Each CysMA residue comprises a primary amine and a carboxylic acid. Surface zeta potential and atomic force microscopy (AFM) studies of the pH-responsive PCysMA brushes confirm that they are highly extended either below pH 2 or above pH 9.5, since they possess either cationic or anionic character, respectively. At intermediate pH, PCysMA brushes are zwitterionic. At physiological pH, they exhibit excellent resistance to biofouling and negligible cytotoxicity. PCysMA brushes undergo photodegradation: AFM topographical imaging indicates significant mass loss from the brush layer, while XPS studies confirm that exposure to UV radiation produces surface aldehyde sites that can be subsequently derivatized with amines. UV exposure using a photomask yielded sharp, well-defined micropatterned PCysMA brushes functionalized with aldehyde groups that enable conjugation to green fluorescent protein (GFP). Nanopatterned PCysMA brushes were obtained using interference lithography, and confocal microscopy again confirmed the selective conjugation of GFP. Finally, PCysMA undergoes complex base-catalyzed degradation in alkaline solution, leading to the elimination of several small molecules. However, good long-term chemical stability was observed when PCysMA brushes were immersed in aqueous solution at physiological pH

Polymerization-Induced Self-Assembly of Block Copolymer Nano-objects via RAFT Aqueous Dispersion Polymerization

In this Perspective, we discuss the recent development of polymerization-induced self-assembly mediated by reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization. This approach has quickly become a powerful and versatile technique for the synthesis of a wide range of bespoke organic diblock copolymer nano-objects of controllable size, morphology, and surface functionality. Given its potential scalability, such environmentally-friendly formulations are expected to offer many potential applications, such as novel Pickering emulsifiers, efficient microencapsulation vehicles, and sterilizable thermo-responsive hydrogels for the cost-effective long-term storage of mammalian cells

Polymerization-Induced Self-Assembly of Galactose-Functionalized Biocompatible Diblock Copolymers for Intracellular Delivery

Recent advances in polymer science are enabling substantial progress in nanobiotechnology, particularly in the design of new tools for enhanced understanding of cell biology and for smart drug delivery formulations. Herein, a range of novel galactosylated diblock copolymer nano-objects is prepared directly in concentrated aqueous solution via reversible addition−fragmentation chain transfer polymerization using polymerization-induced self-assembly. The resulting nanospheres, worm-like micelles, or vesicles interact in vitro with galectins as judged by a turbidity assay. In addition, galactosylated vesicles are highly biocompatible and allow intracellular delivery of an encapsulated molecular cargo

Radical polymerization of biobased monomers in aqueous dispersed media

This review highlights the design and synthesis of biobased monomers from renewable resources for the preparation of latexes in aqueous dispersed media. Biobased polymers have been widely studied and are still a hot topic as environmental concerns and regulations require the use of green chemistry principles as guidelines for the synthesis of new polymer materials. Consideration should equally be given to green polymerization processes such as industrially relevant aqueous emulsion and suspension polymerizations. However, the synthesis and polymerization of biobased monomers through polymerization in aqueous dispersed media have not been sufficiently explored. Hence, constraints and opportunities arising from previous research work in this area will be presented focusing on aqueous (mini)emulsion and suspension polymerizations