Depolymerization of vinyl polymers into monomers is energy-intensive due to the high thermal and chemical stability of the backbone. Depolymerizations of methacrylic polymers are typically conducted above the ceiling temperature and thermal degradation temperature to degrade polymers by bond scission. This work investigates the catalyzed depolymerization of a Clcapped poly(poly(dimethylsiloxane) methacrylate) (P-(PDMS 11 MA-Cl)) polymer mediated by an atom transfer radical polymerization catalyst: copper(II) chloride/tris(2-pyridylmethyl)amine (CuCl 2 /TPMA) at 170 °C. The depolymerization yield, rate, and selectivity were improved by increasing the ratio of [TPMA]/[CuCl 2 ]. Electron transfer from the ligand contributed to the Cu(I) activator (re)generation at high temperature (T > 130 °C), as proven by ultraviolet−visible spectroscopy. The bottlebrush could be partially depolymerized and repolymerized over a few cycles.
The
vulcanization of rubber is a chemical process to improve the
mechanical properties by cross-linking unsaturated polymer chains.
Zinc oxide (ZnO) acts as an activator, boosting the rubbers’
sulfur vulcanization. Maintaining the level of ZnO content in the
rubber compounds as low as possible is desirable, not only for economic
reasons but also to reduce the environmental footprint of the process.
In this contribution, octylamine (OA) capped ZnO nanoparticles (5
nm diameter), prepared through a thermal decomposition method, were
demonstrated to be efficient activators for the sulfur vulcanization
of natural rubber, enabling the reduction of the required amount of
ZnO as compared to commercial systems. The effect of different ZnO
activators (OA capped ZnO/commercial indirect process ZnO) on the
curing characteristics, cross-linking densities, and mechanical performance,
as well as the thermal behavior of rubber compounds, were investigated.
Compared to the commercial indirect process ZnO, OA capped ZnO nanoparticles
not only effectively enhanced the curing efficiency of natural rubber
but also improved the mechanical performance of the composites after
vulcanization. This was interpreted
as, by applying the OA capped ZnO nanoparticles, the ZnO levels in
rubber compounding were significantly reduced under the industrial
vulcanization condition (151 °C, 30 min).
Elucidation of the mutual influence of composition and architecture of polymer canopies on the assembly and mechanical properties of brush particle-based materials holds the promise of advancing the understanding of the governing parameters controlling interactions in hybrid materials and the development of novel functional materials. In this work, the elastic properties of three series of brush particle systems were investigated, differentiated by grafting density as dense, intermediate, and sparse brush systems. Dense and intermediate systems displayed uniform microstructures; the degree of order (measured using Voronoi cell area analysis) increased with grafting density. For dense and intermediate brush particle systems, instrumented indentation analysis revealed an increase of the elastic modulus with the degree of polymerization of tethered chains, in contrast to effective medium predictions. Furthermore, the contribution of ligands to particle interactions increased with decreasing grafting density. The results indicated that the response behavior of particle brush films in tensile-type deformations depends on dispersion interactions between ligands of adjacent brush particles. The more pronounced brush interdigitation in the case of intermediate graft densities enhanced the dispersion interactions between brush particles and hence the modulus of films. A reversed trend in modulus was observed in films of sparse brush particles that also featured the formation of string-like superstructures. Here, the elastic modulus was substantially increased for low-molecular ligands and continuously decreased with increasing degree of polymerization of tethered chains along with a transition from stringlike to uniform morphologies. Independent of grafting density, the elastic modulus of the pristine polymer was recovered in the limit of a high degree of polymerization of polymer ligands.
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