Journal of Polymer Science最新文献

Copolymer particles containing anhydride and amide groups are widely utilized in oilfields and medication releases because of their high specific surface area, excellent biocompatibility, and water solubility. Here, the self-stabilized precipitation (2SP) method was used to create maleic anhydride (MAH)/vinyl acetate (VAc)/acrylamide (AM) terpolymer (PMVA) microspheres. Terpolymer composition was highly dependent on monomer feed ratio and microspheres with diameters in the range of about 228–1048 nm could be prepared by altering reaction parameters. Notably, AM was consumed completely within a short period of time owing to high monomer reactivity, MAH and VAc continuing to copolymerize in an alternating manner. Thus self-assembled core–shell particle with poly(MAH-co-VAc-co-AM) as core and poly(MAH-alt-VAc) as shell (PMVA@PMV) was readily achieved. PMVA particles can be scaled up to application platforms of hydrogel, oil recovery, and scale inhibition. Meanwhile, this contribution broadened the preparation process of core–shell material and can be applied to interface materials by simple modification.

The polymeric materials can simultaneously possess high mechanical properties and outstanding self-healing performance under mild condition have found widespread applications in various fields. However, this type of polymers is exceedingly rare due to the trade-off between mechanical robustness and chain flexibility for healing. In this study, we designed a facile strategy for synergistic integration of dynamic acylsemicarbazide (ASC) bonds and disulfide bonds into polyurethane elastomer by the reaction between 3,3′-dithiobis(propionohydrazide) and isocyanate-terminated Pre-PU. The obtained elastomer ASC-SS-PU not only possesses an outstanding tensile strength (17.1 MPa), good stretchability (735%) and high toughness (57.16 MJ·m⁻³), but also exhibits excellent self-healing performance under mild condition. The healing efficiency of the damaged ASC-SS-PU samples (breakage rate >90%) can reach over 70% healing at 60°C for 40 min, which is much lower than conventional ASC-based PU elastomer. Considering the simple and easy-to-scaleup preparation process and commercially available low-cost raw materials, outstanding mechanical strength and toughness, as well as high healing efficiency under mild condition, the ASC-SS-PU elastomer as self-healing but strong materials have great potential for use in various fields.

In this work, varieties of thermal base generators with nitrogen heterocyclic bases as curing catalysts were synthesized and further blended with photo-crosslinking agents, and photoinitiators to achieve the research goal of the low-temperature curable negative photosensitive polyimide (n-LTPI) photoresist. Due to the addition of thermal base generators, the curing temperature was reduced to 200 °C. Adding 2% 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) pyromellitic acid salt to the photoresist can completely iminate at 200 °C. Through field-emission scanning electron microscope analysis, the film produced high-quality photo-patterns with line and via resolution of 2–5 μm at 5–6 μm film thickness. Compared with existing technologies, our article not only achieves low-temperature curing of photoresists but also improved storage stability, which has great practical value in the field of advanced semiconductor packaging.

The main challenge of fused deposition modeling (FDM) is the limited variety of commercially available semicrystalline polymer materials. Isotactic polypropylene (iPP), with a fast crystallization rate and high crystallinity, tends to undergo extensive volumetric shrinkage during the FDM process, further inducing severe deformation and poor dimensional accuracy in 3D-printed parts. This study aims to develop desirable iPP-based materials for the FDM technique through physically blending iPP and thermoplastic polyester elastomer (TPEE). TPEE retards the nonisothermal crystallization ability of iPP, as indicated by the significant decrease in crystallinity (Xc) from 47.7% for neat iPP to 28.5% for the iPP blend at a weight ratio of 30/70. The suppressed crystallization behavior accounts for a drastic decrease in the warpage degree of the 3D-printed parts. The greater the content of TPEE is, the lower warpage the 3D-printed parts have. Additionally, the presence of TPEE slightly influences the shear viscosity of iPP. As a result, iPP blends exhibit excellent extrudability during a typical FDM process. TPEE also enhances the impact strength of 3D-printed parts by 168% compared to that of injection-molded iPP. Taken together, the iPP blends developed in this work are promising FDM feedstock materials with good dimensional accuracy and excellent impact strength.

This study deals with the fabrication of smart anisotropic composite systems capable of reacting to light stimulus and reversibly providing significant change in the length. Surface-modified carbon nanotubes (CNTs) and poly(pyrrole) (PPy) nanotubes were used as photoactive fillers. Anisotropic composites containing these fillers and poly(N-vinyl formamide) (PNVF) matrix were fabricated using a directional freezing technique with freezable monomer, N-vinyl formamide (NVF), as structure guiding medium and subsequent gamma irradiation polymerization and crosslinking technique. The dielectric properties showed that there is the presence of both relaxation processes α and β, which are significantly influenced by the presence of photoactive filler. The anisotropic distribution of fillers in samples was confirmed using microscopical, electrical conductivity and mechanical properties analysis. Finally, the photoactuation capabilities were investigated and showed enhanced photoactive response for the anisotropic system in the change in the length up to 54 μm after irradiation at 627 nm with a very low light intensity of 6 mW cm⁻² in a fully reversible and repeatable manner. The simple, affordable, and industrially scalable fabrication technique opens an avenue for smart anisotropic photoactive composite systems.

Polyamides (PAs) with aspartame-derived diketopiperazine (DKP) form specific particles and exhibit high heat resistance. In this study, we investigated the stereostructures of aspartic acid and phenylalanine, which constitute aspartame DKP. Diketopiperazines with different stereostructures were synthesized from D- and L-aspartic acid and D- and L-phenylalanine, and LL-, DD-, and LD-type aminodiketopiperazines (LL, DD, and LD-ADKPs) were obtained. These ADKPs differed in their crystal forms depending on their stereoisomeric structures. Furthermore, PAs were formed from these ADKPs via polycondensation using triphenyl phosphite/pyridine, and their heat resistance was approximately 300 °C. The secondary structure of each PA was evaluated by circular dichroism, which suggested that LD-type PAs had a mixed secondary structure of coils and helical structures, unlike the LL and DD types. Precipitated LL, DD, and LLcoDD PAs formed similar particles, whereas the particles of the large LD-type PA had different particle shapes owing to their different conformations.

The control of the microstructures of polymer materials derived from diene-based monomers is crucial, and various synthetic methods, including anionic, radical, and coordination polymerization reactions, have been extensively explored. Here, we demonstrated the coordination polymerization of 2-phenyl[3]dendralenes (P3D) as a diene monomer. The polymerization process using monocyclopentadienyltitanium trichloride (CpTiCl₃) as a catalyst and modified methylaluminoxane (MMAO) as a cocatalyst (CpTiCl₃/MMAO) yielded polymers with an exclusive 4,6-structure that is distinct from those produced by anionic polymerization. Furthermore, the copolymerization of P3D with isoprene and styrene proceeded randomly.

Polymers when confined to a dimension comparable to the length scale of polymer chain coils such as thin films, often lead to molecular relaxation processes distinct from their bulk counterpart. Often observed as thermal and mechanical responses such relaxation has been frequently associated with the squeezing of polymer chains having conformations trapped far from thermodynamic equilibrium and subsequently generating processing-induced molecular recoiling stress. Relaxation in polymer films can be modified by tuning the molecular recoiling stress, which is directly influenced by the preparation conditions of the polymer thin films. Hence a comprehensive understanding of the genesis and relaxation of molecular recoiling stress becomes necessary. Here, we provide insights into the nonequilibrium nature observed in polymer thin films, focusing majorly on the investigations into the molecular recoiling stress using the dewetting technique. The impact of various factors like temperature of dewetting, thickness of films, molecular weight of polymers, and physical aging affecting the relaxation of molecular recoiling stress is discussed. In addition, discussions on the possible mechanisms of relaxation and modification of molecular recoiling stress by varying the spin-coating speed and addition of plasticizers are also provided. An alternate approach which gives a new perspective into the relaxation of molecular recoiling stress considering the entropy generated during the dewetting of polymer films is also included. The present work is expected to give the reader a comprehensive understanding of the characteristics of molecular recoiling stress relaxation occurring in polymer thin films.

Dielectric capacitors are widely used in aerospace, power systems, and other fields. Working environments with ever-increasing temperatures pose a new challenge to energy storage performance. Polyetherimide (PEI) has gained extensive research for its good high-temperature properties. In order to further improve its energy storage performance at high temperatures, many researchers have worked on PEI all-organic composites doping with molecular semiconductors. Previous studies generally only considered the effect of introduced deep traps on macroscopic properties such as electrical conductivity, electrical breakdown, and energy storage performance. It has been shown that only qualitative analyses can be performed from the perspective of charge trapping, and it is difficult to obtain quantitative results. Therefore, this work proposes to study the macroscopic properties of polymer dielectrics by combining charge trapping with molecular displacement. A comprehensive conduction-breakdown-energy storage model was established to explain the influence mechanism of molecular semiconductors on the improved energy storage performance of PEI composites at high temperatures. The molecular semiconductor fillers increase the coefficient of friction between molecular chains, which restricts the movement of molecular chains and also limits charge hopping. Therefore, the dielectrics have higher breakdown strengths and smaller conduction losses, which synergistically enhance the energy storage performance.

Composite material based on polyethylene glycol (PEG) and polypyrrole (PPy) polyrotaxanes both encapsulated into α-cyclodextrins (α-CDs) macrocycle molecules was synthesized by cross-linking reaction. The effect of PPy-αCD polyrotaxane incorporation into the PEG-αCD polyrotaxane matrix, on the structural, morphological, thermal, and dielectric properties was evaluated and compared to the reference material. Scanning electron microscopy spectroscopy indicates different surface morphologies of this material in comparison to the reference one. In addition, the contact angle measurements and surface free energy attest a hydrophilic surface, while the reference material exhibits a hydrophobic surface. More than that, the presence of the PPy-αCD cross-linked into the matrix has a beneficial effect on the thermal properties. The composite material shows an enhanced dielectric constant value of 31,365 at 10 Hz frequency compared to the 38.2 of the reference material, and higher dielectric loss (62,398 vs. 80 at 10 Hz, respectively). The conductivity measurements at 10 Hz frequency indicated for the reference material the value 4.5 × 10⁻¹¹, while for the material with PPy-αCD polyrotaxane, the conductivity is three orders of magnitude higher (3.5 × 10⁻⁸) confirming the improvements of the electrical properties.