This opinion paper offers a scientific view on the current debate of the place of biodegradable plastics as part of the solution to deal with the growing plastic pollution in the world's soil, aquatic, and marine compartments. Based on the current scientific literature, we focus on the current limits to prove plastic biodegradability and to assess the toxicity of commercially used biobased and biodegradable plastics in natural environments. We also discuss the relevance of biodegradable plastics for selected applications with respect to their use and end of life. In particular, we underlined that there is no universal biodegradability of plastics in any ecosystem, that considering the environment as a waste treatment system is not acceptable, and that the use of compostable plastics requires adaptation of existing organic waste collection and treatment channels.

The elasticity of disordered and polydisperse polymer networks is a fundamental problem of soft matter physics that is still open. Here, we self-assemble polymer networks via simulations of a mixture of bivalent and tri- or tetravalent patchy particles, which result in an exponential strand length distribution analogous to that of experimental randomly cross-linked systems. After assembly, the network connectivity and topology are frozen and the resulting system is characterized. We find that the fractal structure of the network depends on the number density at which the assembly has been carried out, but that systems with the same mean valence and same assembly density have the same structural properties. Moreover, we compute the long-time limit of the mean-squared displacement, also known as the (squared) localization length, of the cross-links and of the middle monomers of the strands, showing that the dynamics of long strands is well described by the tube model. Finally, we find a relation connecting these two localization lengths at high density and connect the cross-link localization length to the shear modulus of the system.

We pressure tune the hydrogen bond in Fe-O-H⋅⋅⋅O-P structural segments of mixed-valence barbosalite (Fe 2+ Fe 3+ 2)(PO4)2(OH)2. Infrared spectroscopy evidences changes in softening of O-H stretch modes and excessive profile broadening onset below 10 GPa. Single-crystal X-ray diffraction shows pseudo-symmetrization of the original monoclinic unit cell concurs with these changes in the O-H vibrational mode. These are considered compelling indicators of proton delocalization onset below 10 GPa as hydrogen bonds are strengthened under pressure. Subsequently in the range 10−30 GPa, Fe Mössbauer spectroscopy discerns Fe 2+ ⇔ Fe 3+ valence fluctuations at proximate cations of the hydrogen bonds. When the original crystal potential at an Fe 2+ site is perturbed by proton delocalization at a ligand, electron exchange is induced along Fe 2+ →L→Fe 3+ pathways (ligand L = O or (OH)-of shared octahedral faces). Thus, (Fe 2+ Fe 3+ 2)(PO4)2(OH)2 under pressure exemplifies the interplay between proton (THz) and electron (MHz) dynamics on two disparate time scales in the same condensed phase.