Radical step-growth photopolymerization of dithiol−diene monomer miniemulsion is shown to be a highly efficient, robust, and versatile route to generate film-forming linear poly(thioether) latexes. At extremely fast rates, the process results in high-molecular-weight polysulfide products, exhibiting both semicrystalline and oxidation-responsive properties. Four key issues are addressed as regards the practical implementation of this novel UV-driven waterborne technology: the preparation of a photolatent and colloidally stable thiol−ene monomer miniemulsion, the identification of key experimental parameters controlling reaction kinetics and polymer microstructure, the characterization of film semicrystallinity, and the application of poly(thioether ester) latexes as dual-stimuli-responsive nanocarriers sensitive to both oxidation and hydrolysis.
A laboratory experiment for the determination of the crosslinking density of silicone elastomers is described on the basis of swelling experiments and mechanical tests. In the experiment, the macroscopic swelling and mechanical behaviors of the elastomers were discussed as a function of the cross-linking density, which can be easily controlled by varying the base-to-curing-agent ratio during elastomer synthesis. The crosslinking density and the average molecular weight between cross-links were calculated from the swelling degree at equilibrium through the Flory− Rehner theory and from a simple mechanical model. The results have shown a good convergence of the average molecular weight between crosslinks calculated from the two methods, respectively. On a more general note, the suggested experiments and the associated results offered numerous opportunities for discussions on macromolecular architectures, interactions between polymers and solvents, and mechanical properties of elastomeric materials.
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