Narrow Results

The novel cyclic trithiocarbonate was synthesized by dialkylation of trithiocarbonate anion with 2,2′-bis(bromomethyl)biphenyl in a two-phase system using an onium salt as a phase-transfer agent. Styrene polymerization was carried out in the presence of cyclic trithiocarbonate (CTTC). CTTC undergoes ring opening-polymerization and the incorporated trithiocarbonate moiety derived from CTTC performs as the reversible addition-fragmentation chain transfer (RAFT) agent. Through this mechanism, multiblock polystyrenes containing various narrow polydispersity blocks can be prepared.

Two multi-nuclear titanium complexes [Ti(η⁵–Cp*)Cl(μ–O)]₃(1) and [(η⁵–Cp*TiCl)(μ–O)₂(η⁵–Cp*Ti)₂(μ–O)(μ–O)₂]₂Ti (Cp* = C₅Me₅)(2) have been investigated as the precatalysts for syndiospecific polymerization of styrene. In the presence of modified methylaluminoxane (MMAO) as a cocatalyst, complexes 1 and 2 display much higher catalytic activities towards styrene polymerization, and produce the higher molecular weight polystyrenes with higher syndiotacticities and melting temperatures (T_m) than the mother complex Cp*TiCl₃ does when the polymerization temperature is above 70°C and the Al/Ti molar ratio is in the low range especially.

The monomer reactivity ratios of free radical copolymerization of styrene and methyl methacrylate in carbon dioxide at vapor-liquid equilibrium state (vlCO₂) at 65°C and under 7.5–8.5 MPa were measured. The experimental results showed that, in comparison with the data in bulk copolymerization, the monomer reactivity ratio of St in vlCO₂ increased acompanied by a somewhat decrease in that of MMA. Further analysis of the sequence distributions of these copolymers by ¹H-NMR spectra indicated that there was a significant bootstrap effect in this system. The local monomer concentrations in the proximity of growing free radicals, rather than the true reactivity of monomers or free radicals, were altered by the presence of vlCO₂, leading to the change in monomer reactivity ratios.

Emulsion copolymerization of styrene and ethylene catalyzed by a series of neutral nickel(II) complexes was carried out in an aqueous system to give high-molecular-weight copolymers. The copolymers and emulsions were characterized by an array of techniques including NMR, GPC, TEM, WAXD and DSC. The results indicate that the copolymers obtained are mostly block copolymers of polyethylene with random insertion of styrene units, and their M_w is in the range of 10⁵–10⁶. By enhancing the electron withdrawing of the substituents on the phenoxy ring, the ethylene contents in the copolymers varied from 0 to 52%. The molecular weight distribution of the copolymers was bimodal. With reducing the steric effect of substituents on the aniline ring, the solid contents of the emulsions decreased. The polydispersity of the copolymer varied from 11.1 to 2.8, and the ethylene content in the copolymer was below 10%. The homopolymer of styrene was obtained when the substitutent on the aniline ring was hydrogen.

The aerobic oxidative cleavage of styrene C=C double bonds catalyzed by simple manganese porphyrin is reported. Under the catalysis of chloro(tetraphenylporphinato)manganese, the oxidative cleavage of the carbon-carbon double bond of the styrene with air yields benzaldehyde. Our results show that the oxidative cleavage and the epoxidation of the styrene double bond are the competition reactions in the styrene-manganese porphyrin-air system. The reaction temperature decided the product distribution. Under the conditions of 0.4 MPa air and 30 ppm of chloro(tetraphenylporphinato)manganese, the styrene conversion was 20.0% and the selectivity of benzaldehyde and styrene oxide was 81.7% and 12.7% respectively when the reaction temperature was 110°C. Styrene conversion was 92.5% and the selectivity of benzaldehyde and styrene oxide was 48.1% and 41.2% respectively when the reaction temperature was 120°C.

Today, fossil carbon provides us with fuels (energy), polymers (packaging, insulating and building materials, household utensils, glues, coatings, textiles, 3D-printing inks, furnitures, vehicle parts, toys, electronic and medical devices, etc.) and biologically active substances (drugs (Chapter 9), flavorings, fragrances, food additives, plant protection products, etc.). In this chapter we discover the modern materials of our civilization which are very often polymers derived from oil. They are referred to as “plastics” (annual world production: 380 × 10⁶ tons). Their production consumes 8% of the crude oil extracted (ca. 5 billion tons per year). An increasing part of the plastics originates from renewable resources (less than 10% today, see Section 11.10, bio-sourced plastics). Plastics make life easy for us, but at the underestimated cost of damage to our environment (Figure 8.1) and our health. They contaminate the hydrosphere and the agricultural soil. The atmosphere is also contaminated by microplastics…

This chapter aims to illustrate the research that was conducted in Portugal or in collaboration with Portuguese research groups in the 2011–2022 period on the oxidative conversion of volatile organic compounds (VOCs) to useful building blocks. It concerns the selective oxidation under mild catalytic oxidations of some VOCs (toluene, xylene, ethylbenzene, styrene and n-hexane), which are hazardous to human health and the environment. Both homogeneous and heterogeneous catalysts are discussed.

Core-shell nanoparticles (CSN) with polystyrene (PSt)/organophilic montmorillonite (OMMT) as core and poly (butyl acrylate) (PBA) as shell were prepared through seed emulsion polymerization. The structural characteristics of CSN were examined through scanning electron microscopy and transmission electron microscopy. CSN was spherical, with an evident core-shell structure. The thermal property and rheological behavior of the polypropylene (PP)/ethylene-vinyl acetate (EVA) copolymer composite system filled with different proportions of CSN were systematically investigated by using a thermogravimetric analyzer and an RT-2000 high-pressure capillary rheometer. Results showed that temperatures corresponding to the maximum weight-loss rate and the end of weight loss for PP-EVA/CSN were higher than those of single PP-EVA and CSN when the mass fraction of CSN was 5 wt%. CSN can also improve the thermal performance of PP-EVA. The prepared composites that belonged to non-Newtonian pseudoplastic fluid and the processibility were similar to those of PP-EVA. Shear stress, apparent viscosity decreased as CSN was added; thus, CSN unlikely caused damage to the processing fluidity of PP-EVA, instead, processibility is likely improved.