Macromolecular Chemistry and Physics最新文献

The synthesis and characterization of poly(vinylidene fluoride) (PVDF)-based block copolymers using a metal-free light-catalyzed atom transfer radical polymerization (ATRP) approach are described. A PVDF macroinitiator with C─Br bonds at both ends of the chain is synthesized, and an organic photoredox catalyst (OPRC) is used to control the process. The metal-free process expands the possibilities for the synthesis and application of PVDF-based block copolymers, as it allows the use of monomers that is previously incompatible with classical ATRP due to their interaction with metal catalysts. The synthesized block copolymers are characterized structurally and thermally as powder materials and in thin films. Fourier-transform infrared spectroscopy (FT-IR) analysis revealed that the crystalline phase of PVDF changes when thin films are formed. Specifically, the disappearance of the FT-IR peaks related to the gamma phase and the presence of characteristic peaks related to the alpha and beta phases indicate that film formation rearranged the PVDF chains, leading to changes in their crystalline phases. These PVDF-based block copolymers have unique properties, including high thermal stability, chemical resistance, and piezoelectricity, making them potential candidates for use in various fields, such as biomedical engineering, energy storage, and electronic devices.

This study presents the exploration of sequence-defined polyurethanes (PUs) as a new class of heteropolymers capable of precise conformational control. Utilizing molecular dynamics simulations, the folding behavior of polyurethane chains is investigated of varying lengths (11, 20, and 50 monomers) in both vacuum and aqueous environments. The simulations reveal that the heterogeneous chains systematically refold to approach the designed target structures better than non-designed chains or chains with artificially disrupted hydrogen-bond networks. The subsequent synthesis of an optimized 11-mer sequence (P1) is achieved through solid-phase chemistry, with thorough characterization via NMR, MS, and SEC confirming the accuracy of the predicted sequence and its controlled chain length. Solubility tests showed favorable results across multiple solvents, highlighting the versatility of the designed polymer. This research underscores the potential of sequence-defined polyurethanes to emulate the structural and functional attributes of biological macromolecules, opening new pathways for their application in catalysis, drug delivery, and advanced material design. The findings illustrate a promising direction for the development of synthetic polymers with tailored properties, emphasizing the transformative impact of sequence control in polymer chemistry.

Organic–inorganic composite photochromic coatings receive significant attention in energy utilization and conservation due to their easy application and rapid photoresponse. However, their high sensitivity to moisture limits practical applications. This study fabricates organic–inorganic composite functional coatings using a simple one-pot method, producing materials with excellent photoresponsive, water resistance, and thermal insulation. Unmodified phosphotungstic acid serves as the inorganic photochromic filler, while methacrylate derivatives act as the polymer matrix, resulting in coatings with high initial transparency (over 85%). After 5 min of UV exposure, the samples shift to nearly non-transmittable states in the visible range and maintain color depth through 14 coloring-erasing cycles. Unlike polyvinylpyrrolidone substrates, which absorb moisture and soften quickly, this coating has a static water contact angle of up to 91.7°, showing excellent water resistance. Additionally, the composite material provides effective heat insulation in simulated chamber experiments, lowering the temperature by 15 °C compared to untreated chambers. In summary, this composite coating, with its excellent thermal insulation, rapid light responsiveness, stable cycling performance, and outstanding waterproof capabilities, proves highly suitable for applications such as smart windows, information storage, and building energy efficiency.

The introduction of long and flexible polyether chains in epoxy resins is an effective method to improve their toughness. However, using the hydrophilicity/hydrophobicity of polyether chains to tune their moisture resistance has been overlooked currently. In this work, two types of polyether-based diglycidyl ethers with hydrophilic poly(oxyethylene) (DGEPOE) and relatively hydrophobic poly(oxybutylene) segments (DGEPOB) are synthesized and then binary-cured with commercial diglycidyl ether of bisphenol A (DGEBA), respectively, yielding the corresponding DGEPOE:DGEBA-m:ns and DGEPOB:DGEBA-m:ns based on various ratios. For comparison, pure DGEPOEr, DGEPOBr, and DGEBAr resins are also prepared. Results show that the equilibrium water uptake of DGEPOB:DGEBA-m:ns is at least less than one-fifth of that of DGEPOE:DGEBA-m:ns; meanwhile, the diffusion coefficients of water molecules in DGEPOB:DGEBA-m:ns are also 1–2 orders of magnitude lower than those in DGEPOE:DGEBA-m:ns, demonstrating that the incorporation of hydrophobic POB chains can significantly reduce the hygroscopicity of resins. Moreover, DGEPOB:DGEBA-m:ns not only exhibit superior flexibility and ductility relative to pure DGEBAr, but display exceptional strength and toughness in comparison with pure DGEPOBr. These findings suggest that tuning the hydrophilicity/hydrophobicity of building units of epoxy monomers offers a promising strategy for developing high-performance epoxy materials, especially suitable for humid environments.

Digital light processing (DLP) is emerging as a powerful tool for fabricating tissue engineering (TE) scaffolds, particularly for vascular TE and the development of representative in vitro vascular wall models. For the latter, biomaterials should mimick the biological and mechanical properties of native blood vessels. To fabricate tubular constructs, the DLP-printing process is optimized by exploiting acrylate-endcapped urethane-based (AUP) polymers as the presence of the acrylate end groups render them suitable for DLP printing and desirable mechanical properties arise from the urethane segments. Four AUP variants are synthesized, exploring polyethylene glycol (PEG) and polypropylene glycol (PPG) backbones with varying acrylate functionalities (di-acrylate versus hexa-acrylate), namely UPEG2, UPEG6, UPPG2, and UPPG6. Tubular constructs with precise dimensions and morphology are fabricated. PPG-based AUP polymers exhibit superior computer-aided design/manufacturing (CAD/CAM) mimicry compared to PEG-based derivatives. Construct characterization reveals tunable mechanical properties, with elastic moduli ranging from 45 to 259 kPa, reaching values of the human blood vessels. In particular, UPPG6 shows a two-fold higher elastic modulus compared to UPPG2. All materials show excellent biocompatibility. Additionally, surface modification with gelatin-methacryloyl (GELMA) significantly enhances the cytocompatibility of UPPG2 scaffolds. This study demonstrates the feasibility of fabricating tubular constructs with tunable properties using DLP and AUP polymers.

1-Octene has a very high industrial value as one of the linear α-olefins, but the industrial value is severely reduced when its double bond isomerizes to form endo-octene. Thus, in this paper, the effect of reaction temperature, reaction time, type, and concentration of aluminum compounds on the double-bond isomerization reaction of 1-octene and the inhibition of the isomerization by the inhibitor, have been investigated. The mechanism of 1-octene isomerization is studied by combining gas chromatography-mass spectrometry (GC-MS) and density functional theory (DFT) calculations. Modified methylaluminoxanes (MMAO-3A), triethylaluminum (TEA), or triisobutylaluminum (TIBA) could significantly promote 1-octene to undergo double-bond isomerization reactions and the degree of isomerization of 1-octene increased with increasing concentrations of aluminum compounds. In addition, inhibitors such as isooctanol or isooctylamine, can disrupt the structure of the reactive aluminum species and may retard the double bond isomerization reaction of 1-octene. Therefore, reducing the concentration of aluminum compounds in the ethylene/1-octene high-temperature solution copolymerization system and the timely and sufficient use of an inhibitor at the end of the reaction are both effective in eliminating the 1-octene double bond isomerization.

Polyimide films with low dielectric loss (D_f) at high frequencies are urgently needed owing to the rapid development of high-frequency communication technologies. Herein, various polyimide films with rigid mesogenic units are prepared to address this issue. Improving molecular flexibility has been found to promote crystallization during thermal imidization and, consequently, the formation of liquid-crystal-like polyimide (LCPI) films. The optimal LCPI film exhibits an ultralow D_f value of 0.00178 at 10 GHz owing to the limited intermolecular friction. Furthermore, this LCPI film absorbs significantly less water (0.59%), which endows it with favorable durability of low D_f value in a humid environment. The D_f value of the LCPI film at 10 GHz is only 0.00288 after 24 h of exposure to 60% relative humidity. In addition, the LCPI film exhibits a glass transition temperature, coefficient of thermal expansion, and tensile strength of 371 °C, 21.8 ppm K⁻¹, and 240 MPa respectively, and is therefore a suitable low-dielectric-material candidate.

Despite extensive research, the stabilization mechanism of mesomorphic isotactic polypropylene (iPP) at room temperature has not been elucidated completely. To address this issue, nanoscale structural information is indispensable. In this study, mesomorphic-α phase transition is studied with synchrotron wide-angle diffraction and small-angle X-ray scattering. It is found that during phase transition, the mobile amorphous content remained unchanged, while rigid amorphous fraction (RAF) decreased constantly, accompanied by an increase in long period. Assuming that the increase in long period is induced by the extension of the rigid amorphous coil (RAC), the thickness of RAF (R_RAF) is estimated, which is found to be 2.2 nm. This value is greater than the length of b axis in α crystal cell, which can be the reason that folded-chain iPP clusters in mesomorphic iPP cannot approach closer to form α crystal at room temperature. Besides, with R_RAF, the thickness of smectic layer is estimated, which is found to be 0.9 nm. At this thickness, bulk-free energy cannot compensate for the folded-surface free energy, which can be the other reason that mesomorphic iPP chains cannot transit into α crystal at room temperature. The information obtained in this study is favorable for understanding the stabilization mechanism of mesomorphic iPP.

Polymer membranes of a copolymer ligand (L) coordinated to tetra-coordinated N,N'-ethylene bis(salicylideneiminato) cobalt(II) at the fifth coordinating site of the center cobalt(II), Co(II)S-L, are prepared to measure colorimetrically the color changes in response to rapid reversible oxygen binding simultaneously with slow oxidation under moist conditions to yield Co(III)S-L. The chromaticity point observed in CIELAB is the endpoint of the vector sum of the unit vectors for Co(II)S-L, O₂-Co(II)S-L, and Co(III)S-L, scaled by their respective abundance ratios: (1 − m)(1 − n), m(1 − n), and n, where m is the ratio of O₂-Co(II)S-L to the sum of Co(II)S-L and O₂-Co(II)S-L and n is the ratio of Co(III)S-L to the total of the three cobalt complexes. The observed limited area in CIELAB as a stoichiometric Euclidean space is supported by the following two different reaction processes of the polymer membranes: an oxygen-binding reaction under several different partial pressures of oxygen supplied to the membranes in a short period, during which oxidation of the cobalt(II) complexes is negligible, and an oxidation reaction over a long period at a constant partial pressure of oxygen. The chromaticity points in both processes progress linearly in three different two-dimensional coordinates: a^*b^*, a^*L^*, and b^*L^*.