Macromolecular Chemistry and Physics最新文献

Narrowly dispersed nanoparticles with a diameter below 200 nm were synthesized by oxidative polymerization of aniline in aqueous solutions of branched polyvinyl alcohol, since it is challenging in the presence of linear polyvinyl alcohol. According to IR spectroscopy data, the obtained particles consist of polyaniline and branched polyvinyl alcohol chains interacting through hydrogen bonding. The detected thermotropic change in the order of the catalytic stage of aniline polymerization in aqueous solutions of branched polyvinyl alcohol at 5°C–15°C is due to the reaction's heterogeneous autocatalytic nature. The rate constant growth in the catalytic stage with an increase in the molecular weight and concentration of branched polyvinyl alcohol is shown. On the contrary, the rate constant of the non-catalytic stage of the aniline polymerization decreases with a rise in the stabilizer concentration. The obtained results are explained by the formation of hydrogen bonds between the hydroxyl groups of the polyvinyl alcohol and the monomer, as well as by shielding the surface of dispersed phase particles containing the catalytically active oxidized units of polyaniline chain with a macromolecular stabilizer. Thus, by varying the molecular weight of branched polyvinyl alcohol, it is possible to control the particle size and the rate of aniline dispersion polymerization.

This study explores the synthesis of biochar from kraft lignin, followed by its modification with epichlorohydrin and triethylamine, and its integration into a poly(ester amide urethane) matrix along with bentonite nanoclay particles to produce a polymer nanocomposite via a feasible approach. The comprehensive resulting nanocomposite exhibited remarkable mechanical features, displaying a toughness of 87.45 MJ/m³ and a 160% increase in tensile strength compared to the pristine poly(ester amide urethane) matrix. Furthermore, substantial improvement in thermal properties was observed, with T_g of the nanocomposite reaching 84.56°C, indicating enhanced thermal stability. Notably, the nanocomposite also exhibited inherent biodegradability, reinforcing its environmental sustainability. Beyond its mechanical and thermal performance, the nanocomposite demonstrated significant efficacy as an adsorbent, effectively removing heavy metal ions, viz., Pb(II), Zn(II), and Cu(II) from aqueous solutions, with removal efficiencies of 80.38%, 76.06%, and 70.80%, respectively. Kinetic analyses indicated that the adsorption process closely adhered to the pseudo-second order (PSO) model, while the Langmuir adsorption isotherm provided insights into the sorptive behavior. The nanocomposite also exhibited excellent regeneration potential over five cycles, underscoring its economic feasibility and long-term sustainability as an adsorbent. This study highlights the considerable promise of biochar-based polymer nanocomposites in advancing material properties and environmental remediation applications.

A series of honokiol-based epoxy-siloxane (SHEs) was synthesized through Pt-catalyzed hydrosilylation reactions from honokiol epoxy (HOEP) and terminal hydrogen-containing silicone oils (HS). The SHEs integrate flexible silicone segments, rigid biphenyl skeletons, and curable epoxy groups distributed on both sides of the main chain, just like a fishbone, resulting in an optimal balance of performance. The SHEs exhibit excellent compatibility with conventional epoxy resins. It was found that the SHEs can significantly increase the performance of epoxy resin in terms of the toughness, water resistance, thermal stability, and dielectric properties. SHEs universally enhance the toughness of epoxy resins cured with various hardeners while largely retaining tensile strength. Notably, with rigid hardener such as cycloaliphatic anhydrides or aromatic amines, the epoxy resins toughened by SHEs showed excellent properties: the elongation at break surges to 17.23% without sacrificing tensile strength, accompanied by an impact strength of 32.52 kJ m⁻², with negligible glass transition temperature (T_g) reduction, high hydrophobicity (the water contact angle is more than 90°). The results demonstrated the feasibility of introducing biobased material honokiol into polysiloxanes to prepare a new high-efficiency toughener for commercial epoxy resins (DGEBA).

Poly(phenylene sulfide) (PPS) produced by the sodium sulfide method contains ionized end groups such as sodium mercaptide (-SNa) and sodium 4-(methylamino)butanoate​ (-SMAB), which can be exchanged to proton or other cations by ion-exchange process. Depending on the type of cation and the extent of replacement, PPS performances can vary significantly. In this study, PPS samples with different extents of sodium ionization are prepared by adjusting the pH of PPS aqueous dispersion, then the melt stability is systematically investigated by capillary rheometer. It is found that neutral PPS possesses the best melt stability, while melt viscosity increases with the pH. Moreover, molecular weights before and after melt stability test are compared, neutral and alkaline PPS demonstrate similar minor decrease in molecular weight, while acidic PPS suffers severe degradation. Furtherly, electron paramagnetic resonance spectroscopy (EPR), rotational rheometer, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) are applied to reveal the mechanism behind. Loss of ionized end groups weakens ionic interactions in alkaline PPS, which accounts for reduction of melt viscosity, while protonated end groups in acidic PPS accelerate the formation of free radicals, leading to severe degradation of PPS chains.