Macromolecular Chemistry and Physics最新文献

The production and application of poly(butylene succinate) (PBS) still face challenges such as high production costs, insufficient toughness, and slow biodegradation. This study utilizes the ring-opening condensation polymerization method to prepare PBS copolyesters using succinic anhydride (SAA) and 1,4-butanediol (BDO) as raw materials, with 20 moL% different lengths of linear-chain diols as third monomers (carbon numbers are 3, 5, 6, 8, 9,10, and 12). Both PBS and its copolyesters exhibit high weight average molecular weights (18.8 × 10⁴–26.1 × 10⁴ g moL⁻¹), much higher than those obtained through the traditional conventional direct esterification method. Incorporating the third monomer reduces the glass transition temperature (T_g), crystallinity, and melting point (T_m) of the copolyesters. As the chain length of the third monomer increases, the copolyesters show improved toughness, with the elongation at break and notch impact strength of poly(butylene succinate-ran-dodecylene succinate) (P(BS-ran-DoS)) increasing from 374.1% and 5.6 KJ m⁻² of PBS to 723.2% and 64.8 KJ m⁻², respectively. The degradation rate of the copolyesters modified with short-chain diols increases significantly, and as the chain length of the third monomer increases, the degradation rate of the copolyesters slows down. Therefore, the selection of the third monomer can be used to adjust the properties of the polymer.

Lamellae forming polystyrene-b-poly-2-vinylpyridine diblock copolymer melts are investigated with linear shear rheology and Fourier transformation rheology (FT rheology) to quantify their nonlinear behavior under oscillatory shear via mechanical higher harmonic contributions such as I_3/1(ω₁, γ₀). The determination of the zero-shear nonlinearity ($��{}^3�Q_0��\left(�\omega �\right)��\equiv �{\lim }_{�{\gamma }_0�\to �0�}�I_{�3�/�1�}�/�{\gamma }_0^2�$) by a variation of γ₀ is hindered by the increasing domain alignment at increasing γ₀. Thus, an approach for determining ³Q₀(T) by a variation of the temperature is developed and used. This approach allows obtaining insights on the nonlinear behavior directly at temperature-dependent phase transitions, such as at the order-disorder transition temperature T_ODT of block copolymers. The maximum of ³Q₀ is found to be close to T_ODT. The nonlinearity originating from the connection of the unequal polymer blocks is shown to dominate the overall nonlinearity, and the maximum of ³Q₀(T) correlates to  domain alignment for T < T_ODT.

Polymerization-induced phase separation takes place when a miscible component of the monomer becomes immiscible as the polymer is formed. One example is the polymerization of methyl methacrylate (MMA) in the presence of poly(ethylene glycol) (PEG). Depending on the initial conditions, microscopic structures, including porous structures, co-continuous monolith structures, and particle aggregation structures, are obtained. In this study, the phase separation process is analyzed using an optical microscope and fluorescence microscope. The nucleation or spinodal decomposition in the initial stage, subsequent growth in the microscopic domains, and eventual fixation of the structure are observed. The observed images are analyzed using image analysis software. The particle number and the particle size as a function of reaction time are evaluated. Conversion and molecular weight distribution as a function of reaction time are also analyzed.

L-lactide (LA) is polymerized with ethyl L-lactate or trifluoroethanol as initiators (LA/In = 30/1), and the resulting poly(L-lactide) esters are acetylated with acetic anhydride. The acetylated PLA esters are mixed with SnOct₂, dibutyltin bis(4-chlorophenoxide), or dibutyltin bis(pentafluorophenoxide) in solution and crystallized at 120 °C. The doped crystals are annealed at 140 °C or at 160 °C for 7, 14, and 28 days, and the chemical modifications that occurred in the solid state are monitored by matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectrometry, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC) measurements. All catalysts promoted polycondensation, while no significant formation of cycles is observed. However, in the presence of SnOct₂, disproportionation of chains occurred upon annealing at 120 or 140 °C, and crystallites consisting of extended chains with M_n values ≈3500 – 3600 and low dispersities (Ð < 1.5) are formed.

This article provides reports on the method of surface functionalization modification of graphene nanosheets (GNPs) and aluminum nitride (AlN) through polydopamine and silane coupling agents, respectively. This modification achieves excellent dielectric performance of polyvinylidene fluoride (PVDF) composites by ensuring the uniform dispersion of fillers within the matrix. The synergistic effect between surface-modified GNPs and AlN is conducive to increasing polar PVDF crystals and promoting interface polarization. The prepared PVDF/GNPs/AlN composites exhibit a dielectric constant as high as 45 with a dielectric loss of only 0.044. Meanwhile, the enhanced interface compatibility of composite materials, to a certain extent, reduces interface thermal resistance and forms an effective thermal conduction network, which enhances the heat dissipation capability of electronic devices and presents potential application in the dielectric energy storage.

The development of high-strength and multiple self-healing polymer materials remains a major challenge. In this study, a hybrid self-healable polymer using the combination of intrinsic and extrinsic self-healing is demonstrated. The epoxy resin microcapsules with dynamic disulfide bonded shells are successfully prepared through an interfacial polymerization method, which are then added into the intrinsically self-healable epoxy resin substrate also containing disulfide bonds. The unique combination structure enables the polymer composites to exhibit high mechanical strength and excellent multiple self-healing efficiency. On the one hand, the Young's modulus and tensile strength of the material are enhanced due to the reinforcement effect of the fillers. On the other hand, the extrinsic self-healing strategy of the microcapsules, which released repair agents, can support the intrinsic repairing substrate to improve the self-healing ability of the material. More interestingly, the design of the disulfide bond structure of the microcapsule shell contributes to the high self-healing capability of the material during multiple self-healing processes.

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%).