Polymer最新文献

A thin film of an amphiphilic block copolymer, poly(styrene)-b-poly(4-vinyl pyridine), is investigated at the air–water interface. The surface pressure - area per molecule isotherm and the static compressional modulus provide evidence of two phases, assigned as $L_1$ and $L_2$, respectively. The surface topography and the phase images of these phases obtained using atomic force microscope reveal the presence of surface micelles of different sizes and densities. The dilatational rheology of these phases was investigated using the oscillatory barrier method for different strain amplitudes ($1-5$%) and qualitatively assessed using Lissajous–Bowditch curves. It points out the emergence of nonlinearity (asymmetric shape and distorted ellipse) with an increase in strain amplitude. Using a fast Fourier transform, the amplitudes and the phases of different harmonics of the stress–strain curves were extracted, and the total harmonic distortion was determined. In contrast to $L_1$ phase, the total harmonic distortion for the $L_2$ phase increases monotonically with strain amplitude. Fixing the strain amplitude at 1% (small amplitude regime), the temperature as well as frequency dependence studies of the dilatational moduli were carried out. The dynamic storage moduli of the $L_1$ phase is found to be insensitive to temperature while it decreases for the $L_2$ phase suggesting softening. Further, evidence for solid-like viscoelastic response emerges (explained using the Kelvin–Voigt model) for the $L_1$ phase, whereas the $L_2$ phase show a cross-over behaviour.

With the development of industry, the detection and removal of heavy metal ions from water has received much attention. Janus particles are distinguished from many other materials by their unique structure and functionalization. We proposed a simple photo-initiated seed swelling polymerization method for preparing carbon dot-coated dual-functional Janus particles (Janus@CD), using glycyl methacrylate (GMA) as monomer and ethylene dimethacrylate (EDMA) as crosslinker. In order to modulate the particle morphology during the phase separation process, carbon dot (CD) was added to the reaction system. The results demonstrated that the presence of CD had a significant effect on the shape of Janus particles. Furthermore, Janus@CD could be directly applied in the adsorption and detection for MnO₄⁻. The limit of detection (LOD) was 6.39 nmol L⁻¹, and the maximum adsorption capacity was 23.9 mg g⁻¹, in line with the Langmuir adsorption model. The adsorption equilibrium reached within 30 min. The results demonstrated that dual-functional Janus@CD would present great potential in the detection and enrichment for metal ions.

Blending is an effective way to improve properties of rubbers and develop new materials, so more than 75 % of the rubber consumption in the world is rubber blend. However, blending of thermoplastic elastomers has not yet been emphasized, and few successful examples have been reported. The main challenge for blend systems is compatibility of two components. Herein, a series of (polydimethylsiloxane-based PU)-g-(poly (propylene glycol)-based PU) ((PDMS-PU)-g-(PPG-PU)) graft copolymers with different graft chain lengths and hard segment contents (HSC) were synthesized and utilized as compatibilizers of PDMS-PU/PPG-PU blends. The influence of the structure of compatibilizers on the morphology of blends was investigated, and the compatibilization mechanism was proposed. With the solubilization, the phase structure of blends transforms from “droplet-in-matrix” morphologies to co-continuous ones, and the average size of PPG-PU dispersed phase decreases from 3.5 ± 0.45 μm to 230 ± 60 nm. This is the first time that thermoplastic PDMS-PU/PPG-PU blends with co-continuous structures have been successfully prepared. The properties of blends exhibit synergistic effects. For example, they show high tensile strength of PPG-PU in mechanical properties and unique properties of PDMS in dynamic mechanical properties, weather resistance, water resistance and biocompatibility. In addition, strain sensors were fabricated by introducing carbon nanotubes (CNTs) into the blends, which demonstrated remarkable sensing capability for diverse human body motions.

In the present study, the effects of drawing stress on poly(ethylene terephthalate) (PET)-chain extension prior to fiber-structure formation as well as the mechanical and thermomechanical properties of the resulting fiber were investigated. The amount, persistence length, and extension of molecular chains bearing external force were analyzed from the diffraction of the smectic phase observed after necking. For PET fiber with a molecular weight of 19,600 g/mol drawn at a stress lower than the critical value of 99 MPa, less d-spacing and less amount of the smectic phase, slower crystallization, and longer crystallization-induction time were observed. Furthermore, the critical stress value appeared to decrease with increasing molecular weight. When the drawing stress was less than the critical value, the d-spacing extrapolated immediately after necking decreased rapidly with decreasing drawing stress, and this decrease leads to a decrease in the tensile strength and thermal shrinkage of the drawn fiber.

The emergent biobased polymer poly (ethylene 2,5-furandicarboxylate), PEF, has been studied through an innovative approach based on pole figures and orientation factor calculation. PEF uniaxial stretching was performed with different mechanical conditions (different equivalent strain rates), up to several levels of strain and while considering different post-stretching cooling conditions (interrupted, unloaded and ruptured samples). Samples were stretched and interrupted before and after the Natural Draw Ratio (NDR), the deformation for which the material starts strain-hardening. When PEF strain-hardens, it reveals both an increase of the crystalline orientation and crystallinity ratio with the deformation imposed. Unloading the material at temperature tends to decrease partially crystalline orientation, especially regarding the aliphatic part of the chains. Moreover, stretching PEF up to high strains, superior to the NDR, leads to crystal fragmentation. After all, all experimental results were compared to a texture model. It appears that a texture can be developed upon stretching that is close to a fibre texture, as the furan cycles tend to be parallel to the specimen plane.

Disposing of the wastes generated from the carbon fiber reinforced polymer (CFRP) composite materials after service failure has attracted great attention in recent years. CFRP composites prepared with dynamically covalent cross-linking polymers as matrix resins possess excellent self-healing and recyclability performance, providing an efficient solution to overcome this challenge. However, most of the dynamic cross-linking resins are typically made by high-cost petroleum-derived compounds with extensive use of organic solvents and environmentally unfriendly catalysts. Herein, catalyst-free self-healing and recyclable vanillin-based polyurethanes (V-PUs) via dynamic phenol-carbamate bonds were synthesized by a one-step solvent-free method with a biodegradable PCL as soft segment and biobased vanillin derivative as the chain extender. The optimized V-PUs exhibit Young's modulus of 1.92 GPa, stress at break of 64.98 MPa, glass transition temperature of 95 °C, and over 90 % self-healing and reprocessing efficiency. This excellent self-healing and reprocessing performance can be successfully transferred to the CFRP composite materials fabricated with the V-PUs as matrix resins by hand paste-vacuum bag pressing method. The interlayer shear strength (ILSS) of the composite material is 41 MPa, and the healing efficiency determined by ILSS reaches 85.34 %. Closed-loop recovery of the carbon fiber and matrix resin from the CFRP composite is realized through the solvent dissolution approach due to the dynamic character of the phenol-carbamate bonds, which is of great significance for the development of green economy and sustainable society.

Linear low-density polyethylene (LLDPE) is the most widely produced type of polyethylene resin. In this work, we detailed the synthesis and analysis of two bulky α-diimine Pd(II) complexes. These Pd(II) complexes can efficiently synthesize LLDPE-type polyethylene materials (ρ = 0.91–0.93 g/cm³) through ethylene slow-chain-walking polymerization. More interestingly, benefiting from the cationic bulky Pd(II) complexes, polar-functionalized LLDPEs (ρ = 0.91–0.92 g/cm³) are also produced by copolymerization of ethylene with various polar monomers such as 10-methyl undecanoate, methyl acrylate, 10-undecenoic acid. The copolymerization maintains the slow-chain-walking polymerization feature, resulting in a polar copolymer with a high melting point and low branching density. The results of ¹³C NMR spectral also reveal that polar groups are mainly located at the end of the branches in polar-functionalized LLDPEs.

Polyamide 6 (PA6) is widely utilized, yet it confronts challenges such as susceptibility to thermal oxidative aging and high sensitivity to notch impact during usage. In addressing these issues, two novel toughening macromolecular antioxidants, 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid 2-acrylamidoethyl ester styrene copolymer (PAS) and 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid 2-acrylamidoethyl-N-phenylmaleimide copolymer (PAN), were synthesized via free radical copolymerization. Upon incorporation into PA6, their effects on PA6 performance were investigated. Relative to pure PA6, PA6/PAN and PA6/PAS exhibited significant improvements in fracture elongation, with increases of 136.91 % and 313.83 % respectively, along with notch impact strength enhancements of 18.55 % and 24.89 % respectively. This enhancement can be attributed to PAN and PAS reducing the hydrogen bond density between PA6 molecular chains. Subsequent long-term accelerated thermal aging tests conducted at 150 °C, as well as performance testing of samples before and after aging, revealed that the aging of PA6/PAN and PA6/PAS could be delayed by 4–12 days. The exceptional anti-thermal oxidative aging ability and toughening effect of these two macromolecular antioxidants in PA6 showcase promising prospects for its expanded applications.

Poly(l-lactic acid) (PLLA), recognized as a promising substitute for petroleum-based polymers, has garnered significant attention for its various advantages. However, the practical application of PLLA is limited by its poor toughness. This study introduces a novel approach, using a graft copolymer, poly(vinyl alcohol)-graft-poly(l-lactic acid) (PVA-g-PLLA), synthesized through a "grafting to" method to enhance the compatibility of PLLA/PVA blends. It is demonstrated that even though the graft copolymer promotes crystallization, the resultant ternary blends, especially with a mass ratio of 7:3:1, exhibited an 88.7 % elongation at break, representing a 1642 % improvement over pure PLLA and a 576 % increase over binary PLLA/PVA blends. In addition, incorporating PVA-g-PLLA significantly enhanced the toughness of the PLLA/PVA blends without sacrificing strength, thermal stability, or transparency. Remarkably, the Vicat softening temperature of the blends with a 7/3/1.5 ratio increased to about 94.4 °C, substantially higher than the 59.9 °C observed in PLLA/PVA blends. These findings suggest that the newly developed copolymer and the ternary blends hold substantial promise for creating biodegradable materials that do not compromise performance. It suggests a promising future for these materials in various applications where enhanced durability, thermal stability, and environmental sustainability are crucial.