Mobility Of Polymer Chains Research Articles

Temperature and Deformation-Induced Changes in the Mechanical Properties of the Amorphous Regions of Semicrystalline Polypropylene.

This work is focused on the impact of temperature and deformation on the mechanical properties, specifically the elastic modulus (Ea) of the amorphous regions in semicrystalline polymers, using polypropylene as a case study. It has been shown that increasing temperature results in an Ea decrease due to the enhanced mobility of polymer chains, triggered by the activation of α relaxation processes within the crystalline component. Consequently, rising temperature reduces the "stiffening" effect of the crystalline regions on the interlamellar layers. Temperature decrease close to the glass transition causes a significant increase in the Ea value, reaching nearly 70 MPa. Next, the effects of crystalline/amorphous component orientation and undisturbed crystallite length on Ea were examined in materials deformed using a channel die at various compression ratios. At low compression ratios, Ea decreases nearly 4-fold, primarily due to the fragmentation of lamellar crystals in the absence of, or with relatively low, orientation of the crystalline and amorphous components. Conversely, at higher compression ratios, with minimal crystal fragmentation, increased orientation of both crystalline and amorphous regions along the deformation direction (Ea measurement direction) leads to a substantial increase in Ea. Ultimately, the material with the highest used compression ratio exhibited an Ea value approximately 20% higher than that of the undeformed material.

Study on the Crystallization Behavior of Polyether Ether Ketone Thin Films Under Thermal Annealing

ABSTRACTDue to its excellent biocompatibility, high‐temperature resistance, chemical corrosion resistance, radiation resistance, and ease of processing and shaping, polyether ether ketone (PEEK) has been widely used in the field of oral medicine. In this study, we conducted an in‐depth investigation of the thermal annealing process of PEEK films at different temperatures. The grazing incidence wide‐angle x‐ray scattering (GIWAXS) results indicate that the PEEK molecular chains tend to align in an edge‐on orientation in the film, and annealing at different temperatures leads to the formation of two crystalline phases, A and B, with a spacing of 4.46 Å for (200) A and 4.69 Å for (200) B. The crystallization behavior during the annealing process was characterized using in situ GIWAXS, revealing an increase in the film's crystallinity in the early stages of annealing. Due to enhanced polymer chains mobility, the B phase is formed. However, during annealing at 200°C, the intensity of the (200) B peak initially increases and then decreases, indicating the instability of the B phase, which can be disrupted by excessive molecular mobility. Mechanical property characterization results demonstrate that as the annealing temperature increases, the film's elongation at break and modulus decrease.

Tailoring Dielectric Properties and Dimensional Stability of Poly(Phenylene Ether) Using Bismaleimide Crosslinkers for High-Frequency PCB Applications.

With the increasing demand for high-performance printed circuit boards (PCBs) in the 6G communication era, dielectric substrate materials must exhibit a low dielectric constant (Dk), low dielectric loss (Df), and high dimensional stability. In this study, a series of bismaleimide-incorporated poly(phenylene ether) resins (PPE-BMI) with varying bismaleimide (BMI) crosslinker contents is developed, exhibiting significantly enhanced dielectric properties and dimensional stability, owing to the restricted polymer chain mobility and increased crosslinking density. Dielectric property measurements reveal that the PPE-BMI resins exhibit low Dk and Df values at frequencies above 100GHz, while maintaining an excellent dielectric performance even after an 85 °C/85% relative humidity reliability test. A significant reduction in the coefficient of thermal expansion is observed with an increase in the BMI content. Molecular dynamics simulations are employed to clarify the role of BMI crosslinkers in reducing the free volume, enhancing the crosslinking in the PPE (poly(phenylene ether)) matrix, and influencing the thermophysical properties of PPE-BMI. The infiltration of PPE-BMI into glass fabrics and liquid crystal fabrics highlights their potential for practical use in advanced PCB applications operating at high frequencies.

Enhanced Thermal Conductivity of Thermoplastic Polyimide Nanocomposites: Effect of Using Hexagonal Nanoparticles.

Thermoplastic polyimides have garnered significant interest in the electronic and electrical industries owing to their performance characteristics. However, their relatively low thermal conductivity coefficients pose a challenge. To address this issue, this study focused on the properties of nanocomposites comprising two thermoplastic semicrystalline polyimides R-BAPB and BPDA-P3, one amorphous polyimide ULTEMTM, and hexagonal nanoparticles. Polyimide R-BAPB was synthesized based on 1,3-bis-(3',4-dicarboxyphenoxy)benzene (dianhydride R) and 4,4'-bis-(4'-aminophenoxy)biphenyl (BAPB diamine); polyimide BPDA-P3 was synthesized based on 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and diamine 1,4-bis[4-(4-aminophenoxy)phenoxy]benzene (P3); and amorphous polyimide ULTEMTM was commercially produced by Sabic Innovative Plastics. Using microsecond-scale all-atom molecular dynamics simulations, the effects of incorporating hexagonal nanoparticles with enhanced thermal conductivity, such as graphene, graphene oxide, and boron nitride, on the structural and thermophysical characteristics of these materials were examined. The formation of stacked aggregates was found for graphene and hexagonal boron nitride nanoparticles. It was observed that graphene oxide nanoparticles exhibited a dispersion in polyimide binders that was higher than those in graphene and hexagonal boron nitride nanoparticles, leading to reduced translational mobility of polymer chains. Consequently, the decrease in polyimide chain mobility correlated with an increase in the glass transition temperature of the nanocomposites. Aggregates of nanoparticles formed a pathway for phonon transport, resulting in improved thermal conductivity in polyimide nanocomposites. An increase in the thermal conductivity coefficient of polyimide nanocomposites was observed when the concentration of graphene, graphene oxide, and hexagonal boron nitride nanofillers increased. The enhancement in thermal conductivity was found to be strongest when graphene nanoparticles were added.

Hydrolysis of poly(ester urethane): In-depth mechanistic pathway determination through thermal and chemical characterization

Many structure/property relationships of hydrolyzed poly(ester urethane) (PEU) – a thermoplastic – have been reported. Examples include changes in molecular weight vs. elongation at break and crosslink density vs. mechanical strength. However, the effect of molecular weight (or molar mass) reduction on some physical, thermal, and chemical properties of hydrolyzed PEU have not been reported. Therefore, a large set of hydrolyzed PEU (Estane®5703) samples were obtained from two aging experiments: 1) accelerated aging conducted under various environments (air, nitrogen, moisture) and at 64 °C and below for almost three years, and 2) natural aging conducted under ambient conditions for more than three decades. The hydrolyzed samples were characterized via multi-detection gel permeation chromatography (GPC), thermogravimetric analysis (TGA), modulated differential scanning calorimetry (mDSC), UV–vis spectroscopy, nuclear magnetic resonance (NMR), and Fourier-transform infrared (FTIR) spectroscopy techniques. Hydrolysis of ester linkages in the soft-segments decreases both the molecular weight (Mw) and the melting point (Tm) of Estane (from ∼55 °C to 39 °C). Aging above this Tm, increased mobility of polymer chains and water diffusivity in the PEU matrix alter the PEU degradation pathway from those expected at aging temperatures below this Tm and have significant bearing on the critical molecular weight (MC) at which the physical, chemical, thermal, and mechanical properties of Estane change abruptly. While a MC value of 20 kDa is found for PEU hydrolysis at mild temperatures (e.g., as low as 39 °C), the value of MC increases with increasing aging temperatures. To complement the existing structure/property relationships reported in the literature, more correlations are obtained, which include the effect of Mw on polydispersity, intrinsic viscosity (Mark-Houwink equation), UV extinction coefficient, and dn/dc (GPC analysis) values. Furthermore, we seek to bolster previously reported aging models for PEU by developing a practical model with which the extent of degradation and material performance can be predicted based on aging under different temperature ranges both above and below the melting point of Estane.

HRMAS NMR for Studying Solvent-Induced Mobility of Polymer Chains and Metallocene Migration Into Low-Density Polyethylene (LDPE).

HRMAS (high-resolution magic angle spinning) nuclear magnetic resonance (NMR) spectroscopy of low-density polyethylene (LDPE) affords 1H and 13C NMR spectra with superior resolution. For acquiring HRMAS NMR spectra, the polymer is first swollen with representative organic solvents. Then, the samples are measured with a conventional solid-state NMR spectrometer in the wideline mode or at the low spinning speed of 2 kHz. Anisotropic interactions like CSA (chemical shift anisotropy) and dipolar interactions are reduced due to the additional mobility of the polymer chains in the presence of the solvent within the polymer network. The combined effect of this mobility and MAS leads to signals with substantially reduced halfwidths as compared to classic MAS of the dry polymer. With HRMAS, all signals of the polymer become visible, and the spectra can be used for a quick and easy assessment of the polymer swelling behavior in diverse solvents. Being able to characterize polymers on the molecular level, and identifying the solvents that penetrate the polymer network best, enables the study of post-synthesis modifications of the polymers. It is demonstrated by paramagnetic HRMAS that the metallocene nickelocene (Cp2Ni) penetrates the LDPE network along with the solvent and is homogeneously dispersed in the polymer. SEM images prove that the structure of the polymer is not altered by the presence of a solvent and Cp2Ni. The impact of the paramagnetic Cp2Ni on the 1H signal halfwidth and T1 time of LDPE is studied. HRMAS allows a quick assessment of metal complexes regarding their ability to penetrate the LDPE network and therefore supports future studies of catalytic polymer degradation.

Open-structured silica network based on silane-terminated telechelic polybutadiene for electric vehicle tires

The shift towards electric vehicles (EVs) is essential for a sustainable future. Tire manufacturers face challenges including accommodating extra weight, managing instant torque, reducing noise, and improving driving range. Meeting these demands involves substantially reducing the rolling resistance of tire tread composites while simultaneously enhancing their mechanical stiffness and wear resistance. To overcome these issues, an open-structured silica network based on silane-terminated liquid-like telechelic polybutadienes was introduced into rubber composites. This unique network consists of silica aggregates that are chemically bound together, but exhibit physical separation, enabling rubber chains to permeate. The infiltrated polymer chains were tightly constrained by the network, resulting in a notable increase in the crosslink density and mechanical strength of the composite. Furthermore, the tan δ values at 60 °C showed a notable decrease as a result of diminished interparticle friction caused by isolated silica structures and reduced mobility of polymer chains within the network. These findings provide the tire industry with crucial insights for the development of energy-efficient and durable tires for EVs. By addressing these specific requirements of EVs, our study paves the way for more sustainable tires and contributes to the broader adoption of EVs in a sustainable future.

MgO nanofiller reinforced biodegradable, flexible, tunable energy gap HPMC polymer composites for eco-friendly electronic applications

This study explores the development and characterization of eco-friendly Magnesium Oxide (MgO) nanofiller reinforced hydroxypropyl methylcellulose (HPMC) polymer composites for eco-friendly electronic applications. The prepared nanocomposites are biodegradable and flexible without any additional plasticizer. MgO nanoparticles were synthesized using the solution combustion method and incorporated into HPMC matrix through solution casting method. The structural, mechanical, optical, AC and DC electrical, and degradation properties of the prepared nanocomposites were systematically investigated. X-ray diffraction (XRD) confirmed the successful integration of MgO nanoparticles into the HPMC matrix, with noticeable interactions affecting the crystallinity. Mechanical testing revealed an optimal MgO concentration of 0.2 g, which provided the best balance of strength and ductility, while higher concentrations led to increased brittleness. UV–Vis spectroscopy results evident that the energy gap of nanocomposites can be tuneable with MgO incorporation. The photoresponsivity study indicated that higher MgO content reduce the photocurrent due to agglomeration and defect states. Dielectric studies showed a typical frequency-dependent behaviour, with enhanced dielectric constants at lower frequencies attributed to interfacial polarization. However, increasing MgO content decreased the dielectric constant and loss due to reduced polymer chain mobility and increased resistive pathways. Current-Voltage (I-V) characteristics demonstrated a non-ohmic conduction behaviour with Poole-Frenkel emission identified as the predominant conduction mechanism. Degradation tests in both tap water and soil, demonstrated that the MgO incorporation significantly slowed the degradation rate of the composites, enhancing their durability. These findings suggest that MgO-HPMC nanocomposites hold promise for sustainable and flexible eco-friendly electronic applications.

Metal welding-inspired phase change self-healing strategy applied to high-modulus hydrogel composites

The self-healing efficiencies of polymers are inversely proportional to their modulus, as the recovery of the polymer network heavily relies on the mobility of polymer chains. Therefore, reinvigorated by the metal welding, we have developed S-PAM-SA-x supercooling hydrogels, consisting of polyacrylamide hydrogel networks and inorganic CH3COONa·3H2O phase change materials. Subsequently, rigid self-healing H-PAM-SA-x composites were achieved via self-actuated crystallization-related phase change from the supersaturated hydrogels, resulting in a significant enhancement in mechanical properties. Notably, Young’s modulus experienced an astonishing increase from 0.07 to 387.1 MPa. The H-PAM-SA-130 % composites demonstrated satisfactory self-healing performance based on the phase change of melting and crystallization, as the dominant mechanical carrier was found to be the crystal lattice rather than the PAM network. Leveraging the reversible nature of melting and crystallization, the same position can undergo multiple healing cycles without compromising self-healing efficiencies. Moreover, this distinctive dynamic phase change process significantly expands the range of functional applications, encompassing self-healing, adhesion, and patterns’ replication among others.

Sustainable Composites from Waste Polypropylene Added with Thermoset Composite Waste or Recovered Carbon Fibres

In order to limit the ever-increasing consumption of new resources for material formulations, regulations and legislation require us to move from a linear to a circular economy and to find efficient ways to recycle, reuse and recover materials. Taking into account the principles of material circularity and waste reuse, this research study aims to produce thermoplastic composites using two types of industrial waste from neighbouring companies, namely waste polypropylene (wPP) from household production and carbon-fibre-reinforced epoxy composite scrap from a pultrusion company. The industrial scrap of the carbon-fibre-reinforced epoxy composites was either machined/ground to powder (pCFRC) and used directly as a reinforcement agent or subjected to a chemical digestion process to recover the carbon fibres (rCFs). Both pCFRC and rCF, at different weight ratios, were melt-blended with wPP. Prior to melt blending, both pCFRC and rCF were analysed for morphology by scanning electron microscopy (SEM). The pCFRC powder contains epoxy resin fragments with spherical to ellipsoidal shape and carbon fibre fragments. The rCFs are clean from the matrix, but they are slightly thicker and corrugated after the matrix digestion. Further, the morphologies of wPP/pCFRC and wPP/rCF were also investigated by SEM, while the thermal behaviour, i.e., transitions and changes in crystallinity, and thermal resistance were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The strength of the interaction between the filler (i.e., pCFRC or rCF) and the wPP matrix and the processability of these composites were assessed by rheological studies. Finally, the mechanical properties of the systems were characterised by tensile tests, and as found, both pCFRC and rCF exert reinforcement effects, although better results were obtained using rCF. The wPP/pCFRC results are more heterogeneous than those of the wPP/rCF due to the presence of epoxy and carbon fibre fragments, and this heterogeneity could be considered responsible for the mechanical behaviour. Further, the presence of both pCFRC and rCF leads to a restriction of polymer chain mobility, which leads to an overall reduction in ductility. All the results obtained suggest that both pCFRC and rCF are good candidates as reinforcing fillers for wPP and that these complex systems could potentially be processed by injection or compression moulding.

Water as Dual-Function Plasticizer and Cosolvent in Gel Electrolytes for Dye-Sensitized Solar Cells.

This study presents a novel approach to developing eco-friendly dye-sensitized solar cells (DSSCs) using natural and renewable materials for gel polymer electrolytes (GPEs), reducing reliance on unsustainable solvents. Water is added to polar aprotic solvents, specifically ethylene carbonate/propylene carbonate (EC/PC), across various mass fractions (0:100 to 100:0). An amphiphilic hydroxypropyl cellulose (HPC) natural polymer is employed to formulate GPEs within this water-EC/PC cosolvent system, achieving successful gelation up to 50:50 mass fractions. Incorporating water reduced the gel strength and viscosity of the GPEs. Water acted as a plasticizer, enhancing the polymer chains mobility, and creating a more flexible and permeable structure. This increased ion diffusion coefficients and ion mobility, resulting in a maximum ionic conductivity of 18.17 mS cm-1. The highest efficiency achieved in DSSCs using these GPEs is 5.81%, with elevated short-circuit current density and reduced recombination losses. However, some compositions experienced syneresis, affecting their stability. The GPE with a 40:60 mass fraction exhibited superior long-term stability because it is free from syneresis, though it achieved a lower efficiency (4.83%), making it the best-performing sample. This work demonstrates the feasibility and benefits of using gel polymer electrolytes in an aqueous system, improving DSSC efficiency and sustainability.

Superior proton conductivity of amino acid-modified UiO-66-(COOH)2 embedded in chitosan: Mechanistic insights into the acid-base interactions

We focus on optimizing acid-base interactions and hydrogen bonding networks to achieve enhanced proton conductivity under low relative humidity (RH) and high temperature. By functionalizing UiO-66-(COOH)2 with glutamic acid (Glu) and lysine (Lys), we generate Glu-UiO-66-(COOH)2 and Lys-UiO-66-(COOH)2. These modified materials are subsequently incorporated into chitosan (CS) to produce the composites Glu-UiO-66-(COOH)2@CS and Lys-UiO-66-(COOH)2@CS. The successful incorporation of amino acids and cross-linking between -COOH and -NH2 groups in the composites, confirmed by FTIR and PXRD analyses, significantly enhances the structural integrity and durability by strengthening the network, and reducing polymer chain mobility. Proton conductivity assessments reveal that Lys-UiO-66-(COOH)2@CS-7 exhibits a remarkable conductivity of 0.022 S/cm at 100 % RH and 363 K, outperforming Glu-UiO-66-(COOH)2@CS-7. The lower activation energy (Ea) of 0.28 eV for Lys-UiO-66-(COOH)2@CS-7, compared to 0.336 eV for Glu-UiO-66-(COOH)2@CS-7, highlights the significant improvement in intramolecular acid-base interactions and hydrogen bonding. Furthermore, Lys-UiO-66-(COOH)2@CS-7 maintains notable proton conductivity at 43 % RH, with an Ea of 0.216 eV, demonstrating its efficacy in low-humidity conditions. These findings underscore the profound impact of amino acid modifications and cross-linking on proton conductivity by reinforcing acid-base interactions, hydrogen bonding networks, and proton transfer efficiency.

Crystallinity Reconstruction of Squid-Pen Chitosan into Mechanically Robust and Multifunctional Bionanocomposite Food Packaging Film.

First, we explore the effect of bioacids on the film processing of preprocessed, i.e., deacetylated, chitosan (d-chitosan with molecular weight of 1,000,000 kDa), using monocarboxylic acid (acetic acid), dicarboxylic acid (malic acid), and tricarboxylic acid (citric acid) as model weak acidic solvents to destabilize the hydrogen bonding and transform crystal structures into film. Second, we investigate the chemical and physical toughening effect in the bionanocomposite film composed of cross-linkable multicarboxilic acid, i.e., succinic acid (SA). In doing so, the addition of glycerol as a plasticizer can increase polymer chain mobility, making the biocomposite film more ductile and flexible. The addition of CNC also enhances the tensile strength (41.6%), swelling (43.47%), and oxygen barrier properties (38.81%), as well as significantly improves UV light barrier. The excellent antibacterial properties (99.9% efficiency against S. aureus and K. pneumoniae) of the prepared biocomposite films are found to be independent of the presence of glycerol or CNC. Third, the development of film processability under an industrially relevant process is also demonstrated by doctor blade method. It is found that film processability of the squid-pen's chitosan bionanocomposite can straightforwardly be compatible with and improvable in the presence of poly(vinyl alcohol) employed as a model biodegradable processing aid.

Reversible Giant Barocaloric Effect with Broad Working Temperature Range in an Amorphous Ethylene Propylene Diene Monomer.

The barocaloric effect of a solid material is an intense research topic due to its potential application in solid-state refrigeration. Among the proposed candidates, elastic polymers are distinctive because their barocaloric responses are independent from a pressure-induced phase transition which makes it possible to realize a broad working temperature range in principle. However, the barocaloric performance of most elastic polymers diminishes significantly as temperature decreases. In this work, giant and reversible barocaloric effects were observed in a broad working temperature range from 252 to 345 K in an amorphous polymer of ethylene propylene diene monomer, which are much higher than the investigated crystalline and partially crystallized ones. It is demonstrated that the degree of crystallinity can be a key factor responsible for the mobility of polymer chains and the corresponding barocaloric performance at low temperatures. The reversible giant barocaloric effects, broad working temperature regions, low cost, and absence of pressure-transmitting fluid make the ethylene propylene diene monomer attractive for solid-state barocaloric refrigeration.

Effects of graphene reinforcement on morphology, thermophysical, and mechanical properties of polyvinyl alcohol and polyacrylamide in condensed phases

The subtle interplay of noncovalent interaction in enhancing the compatibility between the graphene-based material and the oligomers of polyvinyl alcohol (PVA) and polyacrylamide (PAM) in the solvent phase is unraveled within the framework of all-atom classical force field-based molecular dynamics (MD) simulations. The decomposition of binding free energy analysis demonstrates that the interaction between polymer segments and graphene (G)-surface crucially emanates from the van der Waals (vdW) interactions, while the adsorption of polymer chains on the graphene oxide (GO)-surface is influenced by vdW and electrostatic interactions. The influence of diverse factors including the strain rate, the size of the nanofiller, the number of oligomers, and the thermal quenching rate on controlling the morphology, mechanical, and thermophysical properties of the graphene-reinforced polymer nanocomposites are further explored. The uniaxial deformation simulations of the graphene-reinforced PVA and PAM matrices show that the interfacial mechanical strength is escalated for the G-PVA nanocomposite. The inclusion of graphene nanofiller reduces the polymer chain mobility and increases the intermolecular interaction, which in turn enhances the toughness of the graphene-polymer composites. Increasing the strain rate raises the yield strength and modulus, making the composites appear stronger and stiffer. As evidenced by the predicted glass transition temperature, the thermal stability of the PVA and PAM matrices is significantly improved by the graphene reinforcement.

Rheological properties, microstructure, and encapsulation efficiency of inulin-type dietary fiber-based gelled emulsions at different concentrations

Gelled emulsion systems offer promising matrices for encapsulating bioactive compounds, enhancing stability, bioavailability, and controlled release. Incorporating inulin-type dietary fibers into emulsion-filled gels can innovate food products. This study explored the impact of inulin concentration (0–15 % w/w) on visual aspect, microstructure, particle size distribution, creaming stability, rheological behavior, and encapsulation efficiency of emulsions and gelled emulsions with clove bud oil rich in eugenol. Regardless of inulin concentration, systems exhibited evenly distributed small oil droplets, ensuring good creaming stability. Emulsions with 10–15 % inulin formed gels upon natural cooling to approximately 30 °C. Viscoelastic properties varied with inulin concentration, attributed to increased polymer chain approximation and mobility. Higher inulin content decreased the transition temperature (66 °C, 56 °C, and 54 °C for 10 %, 12.5 %, and 15 % inulin, respectively). While inulin did not enhance creaming stability, it acted as a physical barrier, improving encapsulation efficiency of eugenol to nearly 100 %. Inulin-based emulsion-filled gels offer potential for functional food development, enriching nutritional value and health benefits.

Proximity-induced FRET and charge-transfer between quantum dots and curcumin enable reversible thermochromic hybrid polymeric films.

This study introduces a novel strategy for developing reversible thermochromic fluorescent films by precisely controlling the nanoscale proximity of boron nitride quantum dots and curcumin molecules within a poly(3-hydroxybutyrate) matrix. The synergistic interaction and Förster resonance energy transfer between these fluorophores result in an energy transfer efficiency of ∼94%. This approach enables tunable color changes in response to temperature variations, governed by the segmental mobility of polymer chains. Practical applications of these films as temperature sensors for water bottles and electronic devices are demonstrated, highlighting their potential in temperature monitoring, smart packaging, and thermal management systems.

Incorporation of myrtle essential oil into hydrolyzed ethyl cellulose films for enhanced antimicrobial packaging applications

This research delved into examining the impact of hydrolysis and incorporation of Myrtle essential oil (MEO) on the film-forming and antimicrobial characteristics of ethyl cellulose polymer (EC). Three plasticizers (glycerol, mono ethylene glycol, and oleic acid) were evaluated for film-forming ability. The composite biofilms' structure was assessed through SEM, XRD, FT-IR, and DSC. Eventually, the combination of hydrolyzed EC with oleic acid yielded a flexible film with optimal thickness. Utilizing GC-MS analysis, α-pinene was identified as the predominant compound within MEO, conferring both antioxidant and antibacterial attributes. FTIR spectroscopy confirmed MEO's participation in the film-forming matrix through hydrogen bonding. By incorporating the MEO into the matrix, the WVP decreased significantly to 6.15*10–12 gmm/hmm2Pa considering that the hydrophobic feature of MEO can block the diffusion of water and decrease the WVP. The melting point and enthalpy of the polymer matrix containing MEO decreased that could be attributable to the EOs plasticizing impact, which increases the polymer chain mobility, and thereby hinders the strong interactions between polymer molecules. From the morphological finding, even at higher concentrations, MEO did not form agglomerations in the film matrix, highlighting its excellent compatibility with the microstructure of the resulting films. The film containing MEO showed the acceptable antioxidant activity. Furthermore, films containing MEO substantially decreased S. aureus biofilm development at 24 and 48 h, compared to P. aeruginosa and E. coli. These findings suggest potential applications of the developed film in packaging and preservation.

Effects of ethyl maltol on properties of starch-based active packaging: Morphology, volatile release and mold inhibition

Ethyl maltol, known for its caramel-like flavor and antimicrobial properties, blends compatibly with baked goods. In this study, ethyl maltol-incorporated starch films were developed as potential active food packaging materials. Films containing 0–10% ethyl maltol were prepared and characterized for their physicochemical, antimicrobial, and barrier properties. Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy confirmed interactions between ethyl maltol and starch, leading to modified thermal properties and enhanced film smoothness. Dynamic mechanical analysis revealed a shift in the relaxation temperature with increasing ethyl maltol content, indicating changes in polymer chain mobility. Water vapor permeability decreased with ethyl maltol incorporation, likely due to reduced hydrophilicity, while oxygen permeability increased, suggesting increased hydrophobicity. Ethyl maltol exhibited antifungal activity against Aspergillus niger, with a maximum inhibition zone of 1.53 mm at 10% loading. When incorporated into starch films, ethyl maltol effectively inhibited fungal growth in butter cake, extending its shelf life by up to three-fold. The controlled release kinetics of ethyl maltol from the films was analyzed using gas chromatography-mass spectrometry (GC-MS), revealing a linear release profile. These results demonstrate the potential of ethyl maltol-incorporated starch films as active, biodegradable food packaging materials with antimicrobial properties and significant shelf-life extension benefits.

Elastomer-based soft syntactic foam with broadly tunable mechanical properties and shapability

Fabrication of lightweight composites using thermally responsive expandable microspheres (EM) embedded in an elastomeric matrix to form syntactic foams offers significant opportunities to create functional and structural composites for diverse applications. The morphology of the EM-elastomer composite on the micro- and macro-scales is significantly influenced by the fabrication sequence and parameters (composition, expansion time/temperature, etc.). Herein, we report the morphological evolution of an EM-elastomer composite through the fabrication processes and elucidate the interaction of relevant fabrication parameters. Unlike the majority of published reports on hard EM composites, the in-situ expansion of the closed-cell foam structure within a soft matrix leads to larger void sizes, and the concomitant expansive force of the EM impacts the polymer chain mobility within the soft composite. At the same time, higher EM loading improves the mechanical properties; the evolved microstructure leads to a lightweight but stiff structure. For the first time the report details the thermal expansion of EM under applied pretension, leading to irreversible prestrain-dependent morphological changes toward anisotropic mechanical properties. Additionally, the composites are shaped under constrained expansion. The study provides a comprehensive guide and expands the pathways for the practical application of EM-embedded soft syntactic foams in aerospace, electronics, wearables, robotics, etc.