ACS Applied Polymer Materials最新文献

Recent studies have shown that the largest employed thermoset family, polyurethanes (PUs), has great potential to be reprocessed due to the dynamic behavior of carbamate linkage. However, it requires high temperatures, especially in the case of aliphatic PUs, which causes side reactions besides the desired exchange reaction. To facilitate the reprocessing of aliphatic PUs, in this work, we have explored the dynamic potential of alkoxyamine bonds in PU networks to facilitate the reprocessing under mild conditions considering their fast recombination ability. Taking advantage of the structural effect of the nitroxide and alkyl radicals on the dissociation energy, two different alkoxyamine-based diols have been designed and synthesized to generate PU networks. Our study shows that replacing 50 mol % of a nondynamic diol chain extender with these dynamic blocks boosts the relaxation times of the networks, enabling reprocessing at temperatures as low as 80 °C.

Currently, polymer-based nanocomposites with high dielectric constant (ε_r) and breakdown strength (E_b) are urgently needed, which are always in a contradictory relationship. In this work, TiO₂ nanowire arrays coated by Al₂O₃ which are synthesized by hydrothermal and ALD are introduced into the PVDF. The results show that the introduction of TiO₂ nanowire arrays with high orientation polarization significantly improves the ε_r of PVDF. In addition, the Al₂O₃ can alleviate the dielectric mismatch at the interface between TiO₂ and PVDF and adjust the distribution of internal electric field, leading to simultaneously improving the E_b of nanocomposites. Finally, the TiO₂@Al₂O₃-24/PVDF nanocomposite achieves a high ε_r of 21 (1 kHz) and energy storage density (U_e) of 15.3 J/cm³, which is more than twice that of pure PVDF (≈ 6.69 J/cm³). This work provides an effective strategy to relieve the contradictory relationship of simultaneous high ε_r and high E_b of dielectrics.

Antifogging coatings are urgently needed in daily life. However, current research efforts seldom focus on enhancing the mechanical wear resistance of coatings or investigating their antifogging properties under wet and dry conditions. Herein, a robust dual-cross-linked polymeric antifogging coating was developed through the UV curing of poly[(methacryloxyethyl)dimethylheptylammonium bromide–acrylic acid] (pMDHAB–AA) and poly(ethylene glycol) diacrylate (PEGDA). Taking advantage of the dual-cross-linked structure and the delicate balance of hydrophilic–hydrophobic components in pMDHAB–AA, the coating presented durable antifogging performances, including long-time antifogging in hot vapor and numerous antifogging in an alternation of wetting and drying and robust mechanical wear resistance. In addition, based on the hygroscopic nature of the quaternary ammonium groups, the coating was endowed with oleophobicity underwater, an ultralow friction coefficient, and antibacterial and resistance-to-bacterial-adhesion performances. More importantly, the antifogging coating plays a crucial role in enhancing substrate transparency by reducing the diffuse reflection. This prepared material addresses current concerns related to antifogging coatings and holds significant potential for applications in various fields, including optical glass, medical devices, agricultural films, etc.

Bio-based phosphorus flame retardants offer significant promise in enhancing the flame retardancy of bioplastics without compromising their environmental friendliness. In this study, a bio-based phosphorus-based flame retardant (PFR) synthesized from epoxidized soybean oil polyol (PESO) was used to enhance the flame-retardant properties of poly(lactic acid) (PLA), aiming to establish the correlation between phosphorus content and the fire behavior of PLA composites. Notably, the study determined that the critical phosphorus content value for improving the PLA rating from NR to V-0 was as low as 0.1 wt % in the composites, with the limited oxygen index (LOI) of PLA increasing from 21.0% to 25.2%. Meanwhile, the introduction of PESO with high phosphorus contents decreased the peak heat release rate (PHRR) and total heat release (THR) of PLA by 5.33% and 9.66%, respectively. Nevertheless, with the complete replacement of the epoxy group by phosphorus ring-opening, PESO loses its plasticizing effect, making it challenging to enhance the elongation at the break of PLA. Finally, the flame-retardant mechanism of PLA/PESO composites was comprehensively analyzed. It was found that the mechanism was also related to the phosphorus contents; high phosphorus was not favorable for the char forming in the condensed phase but promoting the melt dripping and formation of PO^•, PO₂^•, and HPO^• which could trap radicals in the gas phase. This study provides valuable insights into designing PFRs from renewable resources for PLA.

A high strength, swelling resistance, and conductive hydrogel with excellent photothermal effect and antimicrobial property is prepared based on a cellulose frame. First, cellulose is dissolved in a NaOH/urea aqueous solution. The cellulose solution is self-assembled in an ethanol environment to form a cellulose frame. The frame is then immersed in the acrylamide (AM) and 2-methylacryloxyethyl phosphocholine (MPC) solution. A Cel-PA_xM_y cellulose hydrogel is prepared by in situ copolymerization of AM and MPC. Lastly, Cel-PA_xM_y hydrogel is soaked in a tannic acid/ferric chloride (TA@Fe³⁺) solution to prepare the TA@Fe³⁺-Cel-PA_xM_y hydrogel. The obtained hydrogel shows excellent mechanical strength (toughness 600 KJ/m³, Young’s modulus 225 KJ/m³) due to the presence of a rigid cellulose frame. The introduction of TA@Fe³⁺ not only increases the cross-linking density of hydrogels, making hydrogels have extraordinary swelling resistance (swelling ratio 50 ± 20%), but also endows the hydrogels with excellent electrical conductivity (conductivity 1.0 S/m, GF 0.75, response time 572.27 ms), good near-infrared photothermal effect, and outstanding antimicrobial property. This work proposes an effective strategy for the development of high strength, swelling resistance, antimicrobial and conductive zwitterionic hydrogel, which exhibits significant promise for wearable sensors and electronic devices.

As the global economy continues to expand, the issue of oily wastewater pollution has garnered significant attention. Consequently, this paper reports a poly(lactic acid)-based coblended fiber membrane for oil–water separation. The synthesis of a polyurethane–poly(tetrahydrofuran)–polyurethane (PU–PTHF–PU) polymer at 25 °C and its incorporation at 20 wt % into fibrous membranes resulted in a water contact angle of 138°. The coblended fibrous membranes exhibited a tensile strength of 8.05 MPa and an elongation at break of 46.53%, simultaneously improving the rigidity and toughness of the fiber membrane, endowing the poly(l-lactic acid) (PLLA) fibrous membranes with good hydrophobicity and mechanical properties. Featuring a maximum permeate flux of 3898 L·m^–2·h^–1, an oil recovery efficiency of 99.4%, and outstanding stability and durability, the PU–PTHF–PU/PCL/PLLA [PCL = poly(ε-caprolactone)] fibrous membrane represents an ideal solution as an all-biobased biodegradable membrane for oil–water separation.

Thermally induced crystal structure changes in semicrystalline polymers involve solid-to-solid transition or melting of the starting crystal form followed by the recrystallization into different crystal forms. Understanding such crystal-to-crystal transitions by controlling the chain mobility of amorphous chains is rarely studied. Herein, we chose poly(3-hydroxybutyrate) (PHB) to investigate the temperature-induced structural changes in the bulk and aerogel samples and present the role of amorphous chain mobility on structural reorganization during heating. Aerogels of PHB were prepared by freeze-drying the thermoreversible gels and the films were prepared by hot pressing the PHB pellets. Both aerogels and films crystallized into the α form. We observed a major structural reorganization in aerogels upon heating prior to the melting and such a transition was not observed in the melt-crystallized PHB α form. We speculate that the enhanced mobility of the tie chains that are present between the α lamellar crystals during the heating of the aerogel triggered the conformational change from T₂G₂ helical chains to all-trans conformation (T′TT̅′T̅) within the crystal lattice resulted in the crystal-to-crystal (α to α + β) transition.

In this research, two types of metal-free organic–inorganic phosphazene based hybrid porous polymers (HPMs) enriched with phosphorus (P) and nitrogen (N) for gas sorption characteristics were reported. Cyclic phosphazenes were synthesized by condensation of biphenyl methanol with the hexachlorocyclophosphazenes (HCCPs) followed by cross-linking for the fabrication of porous and high surface area moiety designated as HCP-1. Whereas HCP-2 was synthesized with the replacement of polydichlorophosphazene (PDCP) chlorines with biphenyl methanol and later cross-linked in the same manner. Brunauer–Emmett–Teller surface areas of (SA_BETs) of HCP-1 and HCP-2 were 482 and 323 m² g^–1, respectively, whereas pore size distribution was under 1.10 nm. The observation of a higher surface area of HCP-1 is strongly indicative of cyclic N and P long chain backbone [-N═P-]. HCP-1 with a high surface area represented high carbon dioxide (CO₂) adsorption (1.656 mmol g^–1 with quantity adsorbed 37.13 cm³ g^–1 at 273 K/1 bar and 1.35 mmol g^–1 with quantity adsorbed 30.37 cm³ g^–1 at 298 K/1 bar). HCP-2 with a low surface area showed moderate adsorption capacity (1.6 mmol g^–1 with a quantity adsorbed 35.82 cm³ g^–1 at 273 K/1 bar and 1.26 mmol g^–1 with a quantity adsorbed 28.36 cm³ g^–1 at 298 K/1 bar). The values of iodine uptake of HCP-1 and HCP-2 are 148 and 227 wt %, respectively, at 353 K. These results indicate a facile and convenient method to synthesize heteroatom-rich metal-free organic–inorganic phosphazene based hybrid porous polymers for CO₂ and I₂ sorption applications.

Meeting agricultural requirements without a significant impact on the soil-water ecosystem in terms of delivering agrochemicals for seed germination and plant growth necessitates the development of a sustainable and multifunctional controlled release fertilizer carrier. For this purpose, the current study aims at fabricating highly porous urea-biochar/PLA-based agro-augmenting bead-free electrospun mats (EM) with improved physicomechanical performance. The method involved the hydrothermal synthesis of walnut shell-derived biochar, followed by the ball milling, urea loading and subsequent incorporation of urea-loaded ball-milled biochar into porous PLA-based electrospun fibers. The impacts of ball milling and urea loading were evaluated by using morphological (FESEM and TEM), microstructural (FTIR and XRD), and physiochemical (BET and BJH) attributes. To enhance the surface hydrophilicity, PLA-based porous EM was fabricated by altering the concentration of cosolvent (DCM:DMSO) and relative humidity (20–80%). Bead-free and uniform urea/biochar-loaded PLA EM were fabricated by incorporating urea/biochar into PLA precursor solution, and the resultant EM showed improved surface hydrophilicity (with a contact angle of 98.4°), water absorption (∼69.4%), retention capacity (∼17days), and effective release of urea in water (∼11.6%) and soil (∼5.67%). The thermal stability (degradation temperature from 334 to 413 °C) and mechanical properties (from ∼9.6–13.56 MPa) are improved for PLA-based EM upon incorporating urea-biochar. The efficacy of developed EM for promoting plant growth was validated by conducting germination and growth assessments using green gram (Vigna radiata) plants. The results demonstrated a higher germination rate (59.33%), plant height (23.67 cm), root length (9.33 cm), dry weight (0.38g), and fresh weight (0.44g) for plants treated with the EM as compared to the control sample. Thus, the study established optimally designed uniform bead-free microfibrous electrospun constructs with tunable urea release, pointing at an agrotechnology not only enhancing crop yield but also ensuring environmental sustainability as undesirable nutrient-induced secondary complications such as eutrophication and soil quality deuteriation possibilities are largely mitigated.

1D photonic crystals (1DPCs) with bright structural colors are important in a variety of applications, such as sensing, bioimaging, and smart displays. However, the lack of methodologies to produce self-standing 1DPCs remains a challenge for their practical application. Here, we report a method for fabricating ultrathin flexible and brilliantly colored 1DPC films based on the temperature-programmable film-forming property of polymer nanoparticles. Nano poly(styrene-acrylic acid) (P(St-AA)) and TiO₂ are used for 1DPC assembly to achieve high reflectivity and brilliancy. Based on the change of heating temperature and the microbubbles produced during dissolving of the SiO₂ sacrificial layer, the size of the self-standing PCs can be facilely regulated, and the layer-by-layer microstructure remains unchanged. When heated at 85 °C, 1DPC fragments with various brilliant colors are prepared, and they can maintain brilliant structural color for more than one year, which is the first report using 1DPCs as photonic pigments. When heated at 200 °C, the whole 1DPC film can be released from the substrate and retains its mechanical integrity. With this designed method, an ultrathin dry self-standing 1DPC film with a thickness of only 557 nm is first obtained. The self-standing 1DPC films can be patterned easily and transferred to any surfaces such as curved glass bottles and flexible textile fabrics. Moreover, this method will not affect the response of PCs to benzene vapor, which provides a platform for a wearable sensor.