Reactive extrusion (REX) is an important processing and production technique with applications in the field of polymer synthesis, modification and recycling. A full REX design demands a multi-scale approach recognizing...
Although progress in surface-initiated reversible deactivation radical polymerization (SI-RDRP) has already enabled the production of increasingly novel and advanced polymer structures on solid surfaces, fundamental kinetic questions remain regarding the impact of reaction conditions on the molecular properties of synthesized tethered chains. In the current work, we put forward a matrix-based kinetic Monte Carlo (kMC) model, which is based on an implicit SI-RDRP reaction scheme and continuous three-dimensional (3D) representations, capable of following the temporal evolution of the molecular properties of individual free and surface-tethered polymer chains. This is uniquely possible for variable surface curvature (nanoparticle radii from 4.5 to 32 nm; 353 K; monomer: methyl methacrylate), also including the comparison with the limiting case of a flat surface and addressing various (average) RDRP initiator surface coverages. For the tethered chains, we emphasize the prediction of the variation of the molecular height, monomer occupancy, and radius of gyration and also focus on the simulation of the chain length distribution (CLD) to enable a comparison with solution RDRP results. It is shown that confinement effects on the surface lead to the formation of heterogeneous polymer layers with a marked bimodality in the number CLD. This bimodality is, however, wiped out in experimental analysis based on log-molar mass distributions. It is also shown that an increase in the size of the spherical particles and, hence, a decrease in their curvature results in a deterioration of the control over molecular properties, leading to behavior more similar to that of flat surfaces. Average molecular heights and monomer occupancies can vary with a factor of 2. The impact of the targeted chain length is shown to be of lower importance.
In this work, a bivariate kinetic Monte Carlo (kMC) model is constructed to study autoxidation, which is the degradation of polymers in the presence of oxygen. The use of computational...
The three-dimensional configurational arrangement of natural and synthetic network materials determines their application range. Control of the real time incorporation of each building block, hence, all functional groups is desired so that we can regulate macroscopic properties from the molecular level onwards. Here we interconnect kinetic Monte Carlo simulations from the field of chemical kinetics and molecular dynamic simulations from the field of physics. We visualize for (in)organic network material synthesis how the initial building blocks interact timewise and spatially, accounting for variations in inter- and intramolecular chemical reactivity, diffusivity, segmental compositions, branch/network point locations, and defects. We use the kinetic and three-dimensional structural information to construct structure-property relationships based on molecular descriptors such as the molecular pore size or dangling chain distribution, differentiating between ideal and non-ideal structural elements. The generic nature is illustrated by constructing such relationships for the synthesis of organosilica, epoxy-amine and Diels-Alder based networks.
Polylactic acid (PLA) is an important polymer for the replacement of oil-based polymers in the biomedical field as well as for degradable single use polymeric materials. To fully exploit the...
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