Mechanically triggered heterolytic unzipping of a low-ceiling-temperature polymer

Abstract

Biological systems rely on recyclable materials resources such as amino acids, carbohydrates and nucleic acids. When biomaterials are damaged as a result of aging or stress, tissues undergo repair by a depolymerization-repolymerization sequence of remodelling. Integration of this concept into synthetic materials systems may lead to devices with extended lifetimes. Here, we show that a metastable polymer, end-capped poly(o-phthalaldehyde), undergoes mechanically initiated depolymerization to revert the material to monomers. Trapping experiments and steered molecular dynamics simulations are consistent with a heterolytic scission mechanism. The obtained monomer was repolymerized by a chemical initiator, effectively completing a depolymerization-repolymerization cycle. By emulating remodelling of biomaterials, this model system suggests the possibility of smart materials where aging or mechanical damage triggers depolymerization, and orthogonal conditions regenerate the polymer when and where necessary.

Tuning hardness in calcite by incorporation of amino acids

“…To determine the form of the relationship between H and Fc, we first estimate the dislocation line tension  from  = Gb for the material), we find ≈ 9 nN, which is significantly greater than the force required to break a covalent bond (estimated as 1.5 to 4 nN [21][22][23] ), which in turn indicates that the angle  at which the dislocation will cut the molecule will be low (≤ 13˚). Under these conditions, the critical resolved shear stress (c) required for the dislocations cut the particles can be estimated from Using this relationship, and the von Mises criterion to relate Y to c, the hardness is related to the critical resolved shear stress by H ≈ 4.8c.…”

“…Determination of the hardening mechanism of occluded organic additives has proven far more challenging. While species ranging from small molecules 15,16 to peptides 17 , proteins 18,19 , nanoparticles 9,20,21 and fibers 22,23 , have been incorporated in calcite, the effect of these inclusions on mechanical properties is not yet known. Occlusion of 200 nm latex particles within calcite single crystals was shown to reduce their hardness 8 , while the incorporation of polymeric micelles having sizes comparable to those of the protein occlusions in biominerals was shown to increase hardness 9 .…”

Depolymerization Pathways for Branching Lignin Spirodienone Units Revealed with ab Initio Steered Molecular Dynamics

“…Inspired in part by recent experimental and computational efforts in efficient mechanistic study of mechanochemical depolymerization [61][62][63][64][65][66][67] , we recently developed 59 an alternative approach for depolymerization pathway discovery by employing ab initio steered molecular dynamics (AISMD). This technique allows us to both directly predict the results of mechanical lignin depolymerization (e.g., by ball milling 25 ) and, more importantly, to follow the dynamical processes that occur following bond cleavage beyond what can be observed from homolytic bond dissociation energy (BDE) studies.…”

The Role of Mass and Length in the Sonochemistry of Polymers

“…The model uses an approach similar to that proposed by Glynn et al 25 for linear polymers and extended to star polymers by Peterson and Boydston, 27 which has been abundantly used in the literature. 36 Our modeling strategy, however, differs slightly because it permits to obtain the time evolution of the polymer chain length distribution and not simply its evolution in terms of the number of scission events. The detailed equations are reported in the Supporting Information.…”