Up to now, rubber materials have been used in a wide range of applications, from automotive parts to special-design engineering pieces, as well as in the pharmaceutical, food, electronics, and military industries, among others. Since the discovery of the vulcanization of natural rubber (NR) in 1838, the continuous demand for this material has intensified the quest for a synthetic substitute with similar properties. In this regard, synthetic polyisoprene rubber (IR) emerged as an attractive alternative. However, despite the efforts made, some properties of natural rubber have been difficult to match (i.e., superior mechanical properties) due not only to its high content of cis-1,4-polyisoprene but also because its structure is considered a naturally occurring nanocomposite. In this sense, cutting-edge research has proposed the synthesis of nanocomposites with synthetic rubber, obtaining the same properties as natural rubber. This review focuses on the synthesis, structure, and properties of natural and synthetic rubber, with a special interest in the synthesis of IR nanocomposites, giving the reader a comprehensive reference on how to achieve a mimic of NR.

Biobased hydroxyl-terminated polybutadiene (HTPB) was successfully synthesized in a one-pot reaction via metathesis degradation of industrial rubbers. Thus, polybutadiene (PB) and poly(styrene-butadiene-styrene) (SBS) were degraded via metathesis with high yields (>94%), using the fatty alcohol 10-undecen-1-ol as a chain transfer agent (CTA) and the second-generation Grubbs–Hoveyda catalyst. The identification of the hydroxyl groups (-OH) and the formation of biobased HTPB were verified by FT-IR and NMR. Likewise, the molecular weight and properties of the HTPB were controlled by changing the molar ratio of rubber to CTA ([C=C]/CTA) from 1:1 to 100:1, considering a constant molar ratio of the catalyst ([C=C]/Ru = 500:1). The number average molecular weight (M_n) ranged between 583 and 6580 g/mol and the decomposition temperatures between 134 and 220 °C. Moreover, the catalyst optimization study showed that at catalyst loadings as low as [C=C]/Ru = 5000:1, the theoretical molecular weight is in good agreement with the experimental molecular weight and the expected diols and polyols are formed. At higher ratios than those, the difference between theoretical and experimental molecular weight is wide, and there is no control over HTPB. Therefore, the rubber/CTA molar ratio and the amount of catalyst play an important role in PB degradation and HTPB synthesis. Biobased HTPB can be used to synthesize engineering design polymers, intermediates, fine chemicals, and in the polyurethane industry, and contribute to the development of environmentally friendly raw materials.

This work reports on the synthesis of a series of new sulfonated fluorine-containing aromatic polyamides with increasing degree of sulfonation (DS). The chemical structure of the resulting polymers was confirmed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance (¹H NMR) which evidenced the presence of amide and sulfonic groups in the proposed concentrations. Afterwards, we carried out a comparative study of heavy metal ion adsorption in membranes based on these aromatic polyamides. The main purpose was to determine the adsorption capacity of the prepared polymer membranes toward Pb²⁺ and Hg²⁺ in aqueous media at 30°C and pH neutral. The adsorption kinetics was evaluated with the pseudo-first-order and pseudo-second-order models. The adsorption kinetics in all the polyamide membranes followed the pseudo-second-order rate law for both heavy metal ions. It is observed that the adsorption capacities of all the polyamides toward Pb²⁺ ions are higher than those of the Hg²⁺ ions, and these capacities increase as the DS increases. The equilibrium adsorption amounts, q_e, were 11.87 mg/g for Pb²⁺ and 5.17 mg/g for Hg²⁺ ions for the highest sulfonated polymer.