Macromolecular Chemistry and Physics最新文献

This study reports the pair distribution function (PDF) analysis of combined wide- and small-angle X-ray scattering (WAXS/SAXS) profiles of poly(styrene sulfonic acid) (PSSA) grafted poly(ethylene-co-tetrafluoroethylene) polymer electrolyte membranes (ETFE-PEMs) within a wide grafting degree (GD) of 0%–117%. The PDF analysis of WAXS profiles (from Cu-Kα₁ radiation) provides a measure in size of the crystallite domains (5.1–8.7 nm). The extension of the PDF analysis for only SAXS profiles shows the distances of crystallite layers of 25.1–32 nm. In particular, SAXS-PDF analysis is effective in showing the existence of newly generated graft domains with distances ≈60–64 nm, which can not be determined previously by the conventional SAXS analysis. The high similarity in local and higher-order structures observed for polystyrene grafted ETFE films and ETFE-PEMs suggests that the hierarchical structures including the spatial arrangement of large amorphous contents in the membranes can be determined at the graft polymerization step. Note that the presence of newly generated PSSA graft domains at large dimension can explain well the comparable or higher proton conductivity of ETFE-PEMs as compared with commercial Nafion membrane.

Semi-interpenetrating polymer networks (semi-IPNs), composed of two or more polymers, forming intertwined network-architectures, represent a significant type of polymer combination in modern industry, especially in automotive and medical devices. Diverse synthesis techniques and plentiful raw materials highlight semi-IPNs in providing facile modifications of properties to meet specific needs. An initiator-free synthesis of semi-interpenetrating polymer networks via Bergman cyclization (BC) is reported here, acting as a trigger to embed a second polymer via its reactive enediyne (EDY) moiety, then embedded into the first network. (Z)-oct-4-ene-2,6-diyne-1,8-diol (diol-EDY) is targeted as the precursor of the second polymer, swollen into the first polyurethane network (PU), followed by a radical polymerization induced by the radicals formed by the BC. The formation of the semi-IPN is monitored via electron paramagnetic resonance (EPR) spectroscopy, infrared-spectroscopy (FT-IR), and thermal methods (DSC), proving the activation of the EDY-moiety and its subsequent polymerization to form the second polymer. Stress−strain characterization and cyclic stress−strain investigations, together with TGA and DTG analysis, illustrate improved mechanical properties and thermal stability of the formed semi-IPN compared to the initial PU-network. The method presented here is a novel and broadly applicable approach to generate semi-IPNs, triggered by the EDY-activation via Bergman cyclization.

A family of ten amino-containing bis(arylimino)acenaphthene-nickel (II) bromide complexes varied in the electronic properties of para-substituents (R = Me, ⁱPr, ^tBu, OMe, Cl, F, NO₂) as well as two amino-free comparators (R = Me, Cl) are synthesized in good yield from their corresponding unsymmetrical N,N’-ligands. All organic compounds are well characterized by different analysis techniques. On activation with Me₂AlCl, all nickel complexes exhibit moderate to high activities with a maximum activity up to 14.19 × 10⁶ g (PE) mol⁻¹ (Ni) h⁻¹ and deliver narrow dispersed polyethylene (PDI: 1.85–2.65) with adjustable molecular weight values (M_w: 5.27–18.49 × 10⁵ g mol⁻¹). The presence of remote fluoro- group and (4-amino-3,5-dimethylphenyl)(phenyl)methyl group has their own unique influence on activity due to their different electronic and steric properties. Nevertheless, the latter with higher steric hindrance results in better thermal stability of the current catalytic system. Moreover, all polyethylene is highly branched and exhibits typical characteristics of thermoplastic elastomers, especially good mechanical properties (εb up to 1175%) and elastic recovery rate (up to 86%).

Resveratrol and 2-thiophenemethylamine have been employed in the synthesis of a novel tri-functional benzoxazine (RES-th) to develop the bio-benzoxazine monomer. The chemical structure of the synthesized monomer is confirmed by various characterization technics. The polymerization behavior is monitored by in situ Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The in situ FTIR results reveal distinct reaction mechanisms for the three oxazine rings presented in RES-th, with both ether and phenolic Mannich bridge structures observed in the products. The activation energy values of RES-th are calculated to be 119.05, 120.97, and 119.44 kJ mol⁻¹ by Kissinger, Ozawa, and Starink methods, respectively, which are all based on the heat flow curves at various heating temperatures. The thermal stability and flame retardancy of the resulting polybenzoxazine (poly(RES-th)) are investigated by thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC). The values of T_d5 and T_d10 of polybenzoxazine are found to be 356 °C and 399 °C, respectively, with a char yield of 66.3% at 800 °C. The prepared polybenzoxazine also demonstrates nonflammability characteristics with the values of heat release capacity (HRC) and total heat release rate (THR) of 18.65 J (g K)⁻¹ and 2.69 kJ g⁻¹, respectively. These findings suggest that the thermoset, poly(RES-th), is a promising candidate for fire-resistant applications.

Recyclability of polyurethane materials is significant to relieve environmental problems caused by damaged polymers. Inspired by plenty of self-healing properties based on dynamic covalent bonds. A high mechanical strength and thermally reversible polyurethane adhesive are acquired through co-polymerization of poly-1,4-butylene adipate glycol (PBA), soybean oil-based polyol (MESO), and toluene diisocyanate (TDI) whose linear polymer chains are constructed by Diels–Alder reaction between furfuryl alcohol (FA) and bismaleimide (BMI), named DAPU. Further, the obtained polyurethane adhesives show great recyclability, mechanical performance (Whose tensile strength can reach 91.7 MPa), and appropriate self-healing ability through the thermally reversible Diels–Alder covalent bonds and hydrogen bonds between urethane groups, which may pave a way for further development of recyclable materials.

Front Cover: In article 2400042, Ulrich A. Handge and co-workers analyze the effect of crosslinking of a low-density polyethylene (LDPE) on viscoelastic and tribological properties. Wear can be effectively reduced already at a low peroxide concentration of 1 phr. By extending the peroxide concentration up to 20 phr, the coefficient of friction of LDPE against steel is strongly increased because of the large contact area.

Ideas concerning the conceptual existence of macromolecular and colloidal systems found their inception at the beginning of the last century. The experimental technology developed to discover and characterize those systems can be associated with seminal pioneers laying the foundations for microscopic, hydrodynamic, and light scattering approaches. In this perspective, we focus our attention on the origins of the discovery and characterization of macromolecular and colloidal systems with selected examples from the beginnings to the present. This perspective attempts to directly interconnect the design of new macromolecular as well as colloidal systems and the simultaneous development of using advanced characterization techniques for design verification. While not claiming a complete coverage of the entire field of modern polymer science, our selected examples concern the field of life science and the recently and rapidly developing area of energy materials.

Fluorescent hydrogel as an advanced material has been used for anti-counterfeiting, probe detection, and optical devices. A facile strategy to prepare fluorescent hydrogel is developed by carboxymethyl cellulose (CMC) with Europium(III) and polyvinyl alcohol (PVA). The hydrogel forms a physical cross-linking network under mild reaction conditions without using volatile organic chemicals. The addition of CMC-Eu(III) improves the mechanical properties of the hydrogel. At 15% CMC-Eu(III), the hydrogel reaches its maximum tensile and compressive stress, which are 47.25 ± 10.35 and 10.14 ± 1.90 kPa, respectively. Meanwhile, the hydrogels exhibit a ⁵D₀→⁷F₂ characteristic emission peak assigned to Eu³⁺, which emits stable red fluorescence under 254 nm ultraviolet (UV) light. When this hydrogel is applied to paper, the paper showed hidden fluorescent dots under UV light. This additive also enhances the mechanical properties of the paper, which reveals the multifunctionality of this fluorescent hydrogel for anti-counterfeiting and reinforcement.