Recently, new methods have been developed for the utilization of elemental sulfur as a feedstock for novel polymeric materials. One promising method is the inverse vulcanization, which is used to prepare polymeric structures derived from sulfur and divinyl comonomers. However, the mechanical and electrical properties of the products are virtually unexplored. Hence, in the present study, we synthesized a 200 g scale of amorphous, hydrophobic as well as translucent, hyperbranched polymeric sulfur networks that provide a high thermal resistance (>220 °C). The polymeric material properties of these sulfur copolymers can be controlled significantly by varying the monomers as well as the feed content. The investigated comonomers are divinylbenzene (DVB) and 1,3-diisopropenylbenzene (DIB). Plastomers with low elastic content and high shape retention containing 12.5%–30% DVB as well as low viscose waxy plastomers with a high flow behavior containing a high DVB content of 30%–35% were obtained. Copolymers with 15%–30% DIB act, on the one hand, as thermoplastics and, on the other hand, as vitreous thermosets with a DIB of 30%–35%. Results of the thermogravimetric analysis (TGA), the dynamic scanning calorimetry (DSC) and mechanical characterization, such as stress–strain experiments and dynamic mechanical thermal analysis, are discussed with the outcome that they support the assumption of a polymeric cross-linked network structure in the form of hyper-branched polymers.
A series of uniform, macroporous poly(styrene-co-divinylbenzene) microspheres with diameters ranging from 6.6 0.6 to 8.6 0.2 mm was prepared in a multistep procedure involving precipitation polymerization synthesis of polystyrene seed particles, swelling of seed particles with plasticiser and porogen, and polymerization of styrene–divinylbenzene (S–DVB) inside the seed particles. Particles prepared with varying DVB feed ratios had comparable diameters (as evidenced by scanning electron microscopy) with specific surface areas increasing with DVB content from 11 to 467 m2 g1 (measured by nitrogen adsorption). Residual double bonds were converted into azide functionality (through HBr addition and bromo-azide substitution) or alkyne functionality (Br2 addition followed by double elimination) which allowed for CuAAC-click chemistry conjugation with reagents carrying the respective complimentary alkyne or azide functional groups including the fluorescent dye derivatives 7-nitro-4-(prop-2-ynylamino)benzofuran (NBD-alkyne) and Rhodamine B hexylazide synthesised for this purpose. Efficiency of chemical transformations was determined using a combination of CHN and IC elemental analyses, solid state NMR spectroscopy, FT-IR spectroscopy, Raman spectroscopy, and confocal scanning fluorescence microscopy. Although the respective second steps in each modification route (substitution and elimination) suffered from lower yields (35%), porous particles with azide loadings of up to 0.71 mmol g1 and alkyne loadings of up to 0.78 mmol g1 were prepared. Confocal laser scanning microscopy on Rhodamine B-labelled microspheres indicated functionalization throughout the particles featuring a core–shell structure with higher functionalization in the outer layer of particles. Results are expected to contribute to the development of advanced, well-defined, macroporous particles with high, chemically accessible surface areas
UV-Irradiation of azide-functional microspheres for several minutes is shown to result in efficient crosslinking based on nitrene chemistry and to spare a controllable amount of azide functionality which is amenable to click-modification through CuAAC.
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