Chinese Journal of Polymer Science最新文献

Shish crystals are crucial to achieving high performance low-dimensional ultra-high molecular weight polyethylene (UHMWPE) products. Typically, high stretch and shear flow fields are necessary for the formation of shish crystals. In this study, UHMWPE gel films with reserved shish crystals were prepared by gel molding, the structural evolution and properties of UHMWPE films stretched at temperatures of 100, 110, 120 and 130 °C were investigated by in situ small-angle X-ray scattering (SAXS)/ultra-small-angle X-ray scattering (USAXS)/wide-angle X-ray diffraction (WAXD) measurements as well as scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) measurements. Our findings showed that the reserved shish crystals can facilitate the formation and structural evolution of shish-kebab crystals during the hot stretching. Additionally, the reserved shish crystals promote the structural evolution of UHMWPE films to a greater extent when stretched at 120 and 130 °C, compared to 100 and 110 °C, resulting in higher crystallinity, orientation, thermal properties, breaking strength and Young’s modulus. Compared to UHMWPE high-entangled films with reserved shish crystals prepared by compression molding, UHMWPE low-entangled films with reserved shish crystals prepared by gel molding are more effective in inducing the formation and evolution of shish-kebab crystals during the hot stretching, resulting in increased breaking strength and Young’s modulus.

Passive daytime radiative cooling (PDRC) is an innovative and sustainable cooling technology that holds immense potential for addressing the energy crisis. Despite the numerous reports on radiative coolers, the design of a straightforward, efficient, and readily producible system remains a challenge. Herein, we present the development of a hierarchical aligned porous poly(vinylidene fluoride) (HAP-PVDF) film through a freeze-thaw-promoted nonsolvent-induced phase separation strategy. This film features oriented microporous arrays in conjunction with random nanopores, enabling efficient radiative cooling performance under direct sunlight conditions. The incorporation of both micro- and nano-pores in the HAP-PVDF film results in a remarkable solar reflectance of 97% and a sufficiently high infrared thermal emissivity of 96%, facilitating sub-environmental cooling at 18.3 °C on sunny days and 13.1 °C on cloudy days. Additionally, the HAP-PVDF film also exhibits exceptional flexibility and hydrophobicity. Theoretical calculations further confirm a radiative cooling power of 94.8 W·m⁻² under a solar intensity of 1000 W·m⁻², demonstrating a performance comparable to the majority of reported radiative coolers.

Conjugated homopolymers based on six-member rings, e.g., polyfluorene, always exhibit blue emission and conjugated homopolymers based on five-member rings, e.g., polythiophene, can give red emission with low efficiency. In this work, we report a series of new conjugated homopolymers based on six-member rings with high-efficiency deep-red emission. The repeating units of the red light emitting homopolymers are double B←N bridged bipyridine (BNBP) with the boron atoms functionalized with diphenyl, borafluorene, and 2,7-di-tert-butyl-borafluorene groups, respectively. The relationship between the chemical structures and the opto-electronic properties of the monomers and the homopolymers has been systematically studied. The three polymers emit pure red light (λ_max=656 nm) or deep red light (λ_max=693 nm) with fluorescence quantum efficiency in solution higher than 60%. The polymers can be used as the emitters in solution-processed organic light-emitting diodes with red emission and decent device performance. This work indicates a new strategy to design highly efficient light emitting conjugated polymers.

Due to their excellent biocompatibility and biodegradability, aliphatic polyesters are widely used in the biomedical, packaging and agricultural fields, which are usually accessed by the ring-opening polymerization (ROP) of lactones and the catalysts particularly play an important role. Herein a series of quinolinyl-urea catalysts have been synthesized via the reaction between isocyanate and aminoquinoline with an amino group at different substitution positions and characterized. In combination with 7-methyl-1, 5, 7-triazabicyclo[4,4,0]dec-5-ene (MTBD) as a cocatalyst and benzyl alcohol (BnOH) as an initiator, 1-(3,5-bis(trifluoromethyl)phenyl)-3-(quinolin-3-yl)urea (3-QU) was observed to be most active for the ROP of δ-valerolactone (δ-VL). The polymerization conditions were optimized by varying the type of organic base, catalyst concentration and reaction temperature. By changing the ratio of [M]₀/[I], linear polyvalerolactones (PVLs) with different molecular weights and narrow molecular weight distribution were prepared. The kinetic and chain extension experiments were carried out to prove the “living”/controllable feature. And the NMR experiments were used to support the proposal of possible mechanism.

The antioxidant N-isopropyl-N′-phenyl-p-phenylenediamine (4010NA) was dissolved in ethanol and impregnated into silica aerogel (SAG) via vacuum-pressure cycles, yielding composite particles (A-N) with enhanced sustained-release and reinforcing capabilities. The effect of A-N on the mechanical properties and thermal-oxidative aging resistance of styrene-butadiene rubber (SBR) vulcanizates was investigated. TGA and BET assessments indicated that the loading efficiency of 4010NA in SAG reached 14.26% within ethanol’s solubility limit. Incorporating A-N into SBR vulcanizates significantly elevated tensile strength by 17.5% and elongation at break by 41.9% over those with fumed silica and free 4010NA. Furthermore, A-N notably enhanced the thermal-oxidative aging resistance of SBR. After aging for 96 h at 100 °C, the tensile strength and elongation at break of SBR with A-N sustained 70.09% and 58.61% of their initial values, respectively, with the retention rate of elongation at break being 62.8% higher than that of SBR with fumed silica and free antioxidant. The study revealed that A-N composite particles significantly inhibited the crosslinking in SBR’s molecular chains, reducing hardening and embrittlement during later thermal-oxidative aging stages.

Currently, the enhancement in electromagnetic interference (EMI) performance of polymeric composite generally relies on either improving electrical conductivity (σ) for stronger electromagnetic (EM) reflections or tailoring structure for higher EM resonances. Herein, we proposed a novel technique called cyclic pulsating pressure enhanced segregating structuration (CPP-SS), which can reinforce these two factors simultaneously. The structural information was supplied by optical microscopy (OM) and scanning electron microscopy (SEM), both of which confirmed the formation and evolution of segregate structured ultra-high molecular weight polyethylene (UHMWPE)/graphene composites. Then, the result showed that CPP-SS can significantly improve the σ of samples. Ultimately, advanced specific EMI shielding efficiency of 31.1 dB/mm was achieved for UHMWPE/graphene composite at 1-mm thickness and a low graphene loading of 5 wt%. Meanwhile, it also confirmed that the intrinsic disadvantage of poor mechanical properties of conventional segregated structure composites can be surpassed. This work is believed to provide a fundamental understanding of the structural and performance evolutions of segregated structured composites prepared under CPP-SS, and to bring us a simple and efficient approach for fabricating high-performance, strong and light-weight polymeric EMI shields.

In this work, aramid nanoparticles (ANPs) were prepared in dimethyl formamide (DMF) solution containing high impact polystyrene (HIPS) via a bottom-up approach. Transmission electron microscopy (TEM) images showed that the obtained ANPs were evenly distributed in the HIPS matrix without any agglomeration. Chemical composition of the ANPs, i.e., poly(p-phenyl-p-phenylenediamine) (PPTA), was confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffractometer (XRD). The ANP/HIPS composites, obtained after ethanol precipitation, were added to neat HIPS as fillers to fabricate ANP/HIPS composite sheets. The surface roughness and the glass transition temperature (T_g) of the sheets were characterized by atomic force microscope (AFM) and differential scanning calorimetry (DSC), respectively. Compared with neat HIPS, the mechanical properties of the composite sheet were significantly improved, and the Young’s modulus increased from 246.55 MPa to 2025.12 MPa, the tensile strength increased from 3.07 MPa to 29.76 MPa, and the toughness increased from 0.32 N/mm² to 3.92 N/mm², with an increase rate of 721%, 869% and 1125%, respectively. Moreover, the thermal stability of the composites improved with the increase in ANP content.

Polyelectrolytes are charged polymers comprising macromolecules in which substantial portions of the constituent units contain cationic (e.g., pyridinium, ammonium) or anionic (e.g., sulfonate, carboxylate) groups, which possess special functions from the features of counterions, such as dissociation to charged species, mechanical stability, phase behavior, etc. Therefore, functional polyelectrolytes have been widely applied in many fields. In this perspective, we present some progresses in the studies of poly(polyoxometalate)s, denoted as poly(POM)s, as a kind of new charged polymers/polyelectrolytes, by covalent bonding between the inorganic polyoxometalate (POM) clusters and the organic polymer chains. According to the distinct positions of POMs in polymer chain and functions of poly(POM)s, they are divided into the following four categories: crosslinked poly(POM); side-chain poly(POM); backbone poly(POM), including poly(POM)-conjugated polymer hybrid and block poly(POM)-polymer; and POM-based covalent organic framework (PCOF). This perspective introduces the synthesis methods of poly(POM) polyelectrolytes and their macromolecular and aggregate structural characteristics, while also focusing on their properties and functions. Their application areas include catalysis, thermal resistance, optical functions, fuel cells and batteries, etc.

The counterion-mediated hydrogen bonding (CMHB) is related to the hydrogen bonding between bound counterions and polyelectrolyte chains in polyelectrolyte systems, where the counterions can both electrostatically bind to the charged groups of polyelectrolyte chains and act as hydrogen bond donors or acceptors to form hydrogen bonds with the hydrogen bond sites associated with polyelectrolyte chains simultaneously. A large number of literatures illustrate that strong polyelectrolytes (SPs) are insensitive to pH, which severely limmits the applications of SPs as smart materials. However, our studies have demonstrated that the CMHB makes SPs pH-responsive. This perspective discusses the mechanism of pH responsiveness of SPs and the pH-tunable properties of SPs, based on the pH-controlled CMHB effect. The future research directions on the pH responsiveness of SPs are also discussed here. It is anticipated that the study of the pH responsiveness of SPs not only will provide a new understanding of the fundamental properties of SPs, but also will greatly expand the applications of SPs in the field of smart materials.

A variety of electromagnetic wave absorption materials (EMWAs) have been reported, but the integration of powder materials and multifunctional devices should be investigated in-depth to adapt to practical demands. Herein, carbon-coated cobalt composites were prepared by adsorbing magnetic metal cations into an anionic crystalline framework through an electrostatic encapsulate process. Excellent reflection loss (RL_min) of −40.49 dB and effective absorption bandwidth (EAB) of 5.36 GHz (RL<−10 dB, 10.4–15.76 GHz) was achieved with an optimal radar cross section (RCS) reduction of 34.9 dB·m² for the sample tested. For commercial applications, Co@CN-4 was integrated into sodium carboxymethyl cellulose (CMC) aerogel to create an ultra-lightweight composite aerogel that is compressive resistant and heat-holding while also having photothermal conversion capabilities.The hydrophobic modification makes it more widely useful. This study provides a new strategy for EWAMs to integrate versatility and improve their application prospects.