Low Glass Transition Temperature Research Articles

Incorporation of self-heating effect into a thermo-mechanical coupled constitutive modelling for elastomeric polyurethane

Elastomeric polyurethane (EPU) is characterised by distinctive mechanical properties, including high toughness, low glass transition temperature, and high impact resistance, that render it indispensable in diverse engineering applications from soft robotics to anti-collision devices. This study presents a thermo-mechanically coupled constitutive model for EPU, systematically incorporating hyperelasticity, viscoelasticity, thermal expansion, and self-heating effect in a thermodynamically consistent manner. Experimental data, obtained from previous studies, are then used for parameter identification and model validation, including iterative updates for temperature parameters considering the self-heating effect. Subsequently, the validated model is integrated into finite element codes, i.e., user subroutine to define a material’s mechanical behaviour (UMAT) based on the commercial finite element software ABAQUS, for the computation of three-dimensional stress-strain states, facilitating the analysis of the structural response to various mechanical loads and boundary conditions. The results obtained from simulations are compared with analytical solutions to confirm the precision of Finite Element Method (FEM) implementation. The self-heating effect is further analysed under different strain rates and temperatures. To validate the engineering significance of the FEM implementation, a plate with a hole structure is also simulated. In conclusion, this research provides a robust tool for engineers and researchers working with soft materials, enhancing their understanding and predictive capabilities, notably addressing the self-heating effect in thermo-mechanical behaviours.

Rational Design of Nitride Phosphor-In-Glass with Robust Stability and Photoluminescence Performance.

Phosphor-in-glass represents a promising avenue for merging the luminous efficiency of high-quality phosphor and the thermal stability of a glass matrix. Undoubtedly, the glass matrix system and its preparation are pivotal factors in achieving high stability and preserving the original performance of embedded phosphor particles. In contrast to the well-established commercial Y3Al5O12:Ce3+ oxide phosphor, red nitride phosphor, which plays a critical role in high-quality lighting, exhibits greater structural instability during the high-temperature synthesis of inorganic glasses. A telluride glass with a refractive index (RI = 2.15@615 nm) akin to that of nitride phosphor (∼2.19) has been devised, demonstrating high efficiency in photon utilization. The lower glass-transition temperature plays a crucial role in safeguarding phosphor particles against erosion resulting from exposure to high-temperature melts. Phosphor-in-glass retains 93% of the quantum efficiency observed for pure phosphor. The assembled white light-emitting diodes module has precise color tuning capabilities, achieving an optimal color rendering index of 93.7, a luminous efficacy of 80.4 lm/W, and a correlated color temperature of 5850 K. These outcomes hold potential for advancing the realm of inorganic package and high-quality white light illumination.

Facile Preparation of a Transparent, Self-Healing, and Recyclable Polysiloxane Elastomer Based on a Dynamic Imine and Boroxine Bond.

Transparent polysiloxane elastomers with good self-healing and reprocessing abilities have attracted significant attention in the field of artificial skin and flexible displays. Herein, we propose a simple one-pot method to fabricate a room temperature self-healable polysiloxane elastomer (HPDMS) by introducing dynamic and reversible imine bonds and boroxine into polydimethylsiloxane (PDMS) networks. The presence of imine bonds and boroxine is proved by FT-IR and NMR spectra. The obtained HPDMS elastomer is highly transparent with a transmittance of up to 80%. The TGA results demonstrated that the HPDMS elastomer has good heat resistance and can be used in a wide temperature range. A lower glass transition temperature (Tg, -127.4 °C) was obtained and revealed that the elastomer is highly flexible at room temperature. Because of the reformation of dynamic reversible imine bonds and boroxine, the HPDMS elastomers exhibited excellent autonomous self-healing properties. After healing for 3 h, the self-healing efficiency of HPDMS reached 96.3% at room temperature. Moreover, the elastomers can be repeatedly reprocessed multiple times under milder conditions. This work provides a simple but effective method to prepare transparent self-healable and reprocessable polysiloxane elastomers.

Synthesis, characterization and performance evaluation of different alkyl chain lengths flame-retardant plasticizers for poly(vinyl chloride) derived from sustainable vanillic acid

The current market for poly(vinyl chloride) (PVC) plasticizers is dominated by flammable petroleum-based compounds, accounting for over 80 % of the total share. Due to their high flammability, the search for novel approaches to enhance the fire resistance of flexible PVC has gained urgency. However, traditional flame-retardant schemes suffer from shortcomings such as poor compatibility, inferior long-term performance, and weak mechanical properties. Herein, we synthesized a novel biobased flame-retardant plasticizer (VAn-P) using vanillic acid as a skeleton. This plasticizer exhibits remarkable properties, including a substantially lower glass transition temperature compared to unplasticized PVC. The binding energy between VAn-P and PVC is calculated to be –33.30 kcal/mole, indicating a strong interaction. Furthermore, the maximum elongation at break of VAn-P plasticized PVC is 16 times higher than that of unmodified PVC. All PVC samples plasticized with VAn-P achieved a UL-94 VTM-0 rating. TGA-FTIR analysis revealed that the flame-retarding mechanism of VAn-P involves solid-phase action, significantly delaying the dehydrochlorination process of PVC. Moreover, VAn-P exhibits superior migration resistance compared to dioctyl phthalate (DOP). We also investigated the effects of alkyl chain lengths in VAn-P on various properties of PVC blends, including thermal stability, flame retardancy, mechanical properties, and optical performance. The toxicity of vanillic acid-based flame-retardant plasticizer has undergone an initial assessment. Overall, this green plasticizer is expected to endow polymers with high plasticizing performance and flame retardancy, providing a novel and sustainable approach for the synthesis of functional plasticizers.

Self-healing photo-polymerized thiol-ene networks utilizing bio-based hexaallylated compounds derived from L-cystine and citric acid

Bio-based vitrimers have received considerable attention owing to their contributions to carbon neutrality and resource and energy savings. The photopolymerization of hexaallylated compounds (A6CST and A6UDC) derived from L-cystine and citric acid with disulfide-containing polyether dithiol (LP-12) and pentaerythritol-based tetrathiol (S4P) at an allyl:thiol ratio of 1:1 produced thiol-ene network films. Fourier-transform infrared spectroscopy of the cured films revealed that the thiol-ene reaction of the thiol and allyl groups was almost complete. Degrees of swelling of the cured films decreased with an increasing LP-12/S4P ratio. The A6CST- and A6UDC-cured films with higher flexible LP-12 fractions (i.e., higher disulfide contents) exhibited lower glass transition temperatures (Tgs), tensile strengths, and tensile moduli, and could be healed by treatment at a lower temperature and shorter time. The A6CST/S4P cured film was healed by treating at 100 ℃ for 24 h, whereas the A6UDC/S4P cured film without disulfide bond was not healed by the same treatment. The A6CST-based film with the highest LP-12/S4P ratio exhibited the highest healing efficiency (99 %) after treatment at room temperature for 10 h, and self-healed at least three times.

SIS derivative as a novel delivery system for ibuprofen

Ibuprofen is a commonly used analgesic due to its effectiveness, but its half-life is relatively short. Therefore, finding an appropriate delivery system is a significant challenge. In this study, we designed a new controlled release carrier for ibuprofen using a biocompatible poly(styrene-b-isoprene-b-styrene) triblock copolymer. For this purpose, the polyisoprene block was modified with 2-mercaptoethanol or ethanolamine to introduce hydroxyl groups. These linkers allowed the incorporation of the drug through a covalent bond. The modified copolymers were characterized using spectroscopic techniques, including 1H NMR, FTIR-ATR, and UV-Vis, which confirmed successful synthesis. The thermal method revealed that the new delivery system has a lower glass transition temperature than its precursor, verifying the incorporation of the hydrophobic drug. Furthermore, enzymatic release of ibuprofen was studied under physiological conditions and was found to be slow and sustained over time. The in vitro biocompatibility of the release system was evaluated using RAW264.7 monocytes. It was found that cells were able to adhere and proliferate onto the matrices. Additionally, the cells growing on ibuprofen-substituted SIS produced low levels of nitric oxide, a marker of cytotoxicity, when compared to cells growing on tissue culture plates. Taken together, the findings indicate that the polymer may serve as a promising delivery system for ibuprofen with potential biological applications.

Flame-retardant vinyl ester resins enabled by phosphorus-containing 1-vinylimidazole salts with different phosphorus oxidation states

Different reactive flame retardants have been extensively developed for vinyl ester resins (VERs), but very few of them can yield a flame-retardant resin that meets defined standards (e.g. UL-94 V-0 rating). In this work, phosphorous-containing 1-vinylimidazole salts (called VIDHP and VIDPP) were synthesized through the facile neutralization of the acid and 1-vinylimidazole. VIDHP and VIDPP were then applied as flame-retardant crosslinking agents of VERs, by which phosphorus-containing groups could be incorporated into the resin chain via ionic bonds. VIDHP/VER and VIDPP/VER showed a high curing activity and can be well cured in moderate temperatures. With 20 wt.% additions of VIDHP and VIDPP, VIDHP20/VER, and VIDPP20/VER presented a limiting oxygen index value of 29.7 % and 28.4 %, respectively, with the latter achieving a UL 94 V0 rating. In the cone calorimetric test, compared to the unmodified VERs, VIDPP20/VER exhibited large reductions in the peak heat release rate, total heat release rate, and total smoke release rate while VIDHP20/VER demonstrated comparatively inferior performance in terms of the heat release. VIDHP20/VER and VIDPP20/VER showed good thermal stability and presented a little lower glass transition temperature than the control sample. VIDPP with a low phosphorus oxidation state (+1) demonstrated high flame-retardant activities in the gaseous phase, whereas VIDHP with a high phosphorus oxidation state (+5) primarily exhibited efficacy in the condensed phase.

Dietary fibers effects on physical, thermal, and sensory properties of low-fat ice cream

This study investigated the effect of incorporating dietary fibers, inulin, acacia, oat, and apple, in a low-fat vanilla ice cream. A significant increase in the ice cream mixture viscosity was observed with the addition of dietary fibers. Significant differences (p < 0.05) were observed in the crystallization temperature when apple and oat fibers were used. Additionally, low-fat dietary fiber ice creams displayed statistically lower (p < 0.05) glass transition and melting temperatures than full-fat ones, with the most pronounced reductions observed for samples enriched with acacia and apple fibers. Dietary fibers affected (p < 0.05) the sensory profile of low-fat ice cream. However, inulin and acacia fibers samples showed a sensory profile comparable to the full-fat ice cream for nearly all attributes. These findings suggest that utilizing inulin and acacia fibers in low-fat ice cream yields characteristics of full-fat, underscoring the potential for crafting high-quality, reduced-fat ice cream products.

Mechanical, Thermal, and Physicochemical Properties of Filaments of Poly (Lactic Acid), Polyhydroxyalkanoates and Their Blend for Additive Manufacturing.

Polymeric blends are employed in the production of filaments for additive manufacturing to balance mechanical and processability properties. The mechanical and thermal properties of polymeric filaments made of poly (lactic acid) (PLA), polyhydroxyalkanoates (PHA), and its blend (PLA-PHA) are investigated herein and correlated to their measured structural and physicochemical properties. PLA exhibits the highest stiffness and tensile strength, but lower toughness. The mechanical properties of the PLA-PHA blend were similar to those of PLA, but with a significantly higher toughness. Despite the lower mechanical properties of neat PHA, incorporating a small amount (12 wt.%) of PHA into PLA significantly enhances toughness (approximately 50%) compared to pure PLA. The synergistic effect is attributed to the spherulitic morphology of blended PHA in PLA, promoting interactions between the amorphous regions of both polymers. Thermal stability is notably improved in the PLA-PHA blend, as determined by thermogravimetric analysis. The blend also exhibits lower cold crystallization and glass transition temperatures as compared to PLA, which is beneficial for additive manufacturing. Following additive manufacturing, X-ray photoelectron spectroscopic showed that the three filaments present an increase in C-C and C=O bonds associated with the loss of C-O bonds. The thermal process induces a slight increase in crystallinity in PHA due to chain reorganization. The study provides insights into the thermal and structural changes occurring during the melting process of additive manufacturing.

Thermal Radiation Annealing for Overcoming Processing Temperature Limitation of Flexible Perovskite Solar Cells.

Common polymeric conductive electrodes, such as polyethylene terephthalate (PET) coated with indium tin oxide, face a major challenge of their low processing-temperature limits, attributed to PET's low glass transition temperature (Tg of 70-80°C). This limitation significantly narrows the scope of material selection, limits the processing techniques applicable to the low Tg, and hinders the ripened technology transfer from glass substrates to them. Addressing the temperature constraints of the flexible substrates is impactful yet underexplored, with broader implications for fields beyond photovoltaics. Here we introduce a new thermal radiation annealing methodology to address this issue. By applying above Tg radiation annealing in conjunction with thermoelectric cooling, we successfully create highly ordered molecular packing on PET substrates, which are exclusively unachievable due to PET's low thermal tolerance. As a result, in the context of perovskite solar cells, this approach enables the circumvention of high-temperature annealing limitations of PET substrates, leading to a remarkable flexible device efficiency of 22.61% and a record fill factor of 83.42%. This approach proves especially advantageous for advancing the field of flexible optoelectronic devices. This article is protected by copyright. All rights reserved.

Degradable polycaprolactone/buffer composites as pH regulating carrier materials for drug delivery and 3D printed biomaterials

Polymeric materials such as biodegradable polycaprolactone (PCL) have garnered significant attention for their utility in biomedical applications. With its notable low glass transition temperature (Tg), PCL exhibits flexibility at physiological temperatures, rendering it an ideal candidate for drug delivery systems, particularly in fibrous form. This suitability is particularly pronounced when these fibres are designed for placement within periodontal pockets resulting from periodontitis. However, the degradation of PCL yields acidic by-products, potentially impacting adjacent dental structures. To address this, several composites comprising PCL and buffering agents (CaCO3, MgCO3, NaHCO3, Na2HPO4, and TRIS) were processed to scaffolds using fused deposition modelling. For fine mineral powders (MgCO3, Na2HPO4) resulted in an extrudability of up to 20 wt% added to the PCL, whereas otherwise 30 wt% added buffer could be processed without any problems. The primary objective of these composites is to modulate the pH within the gingival crevicular fluid (GCF) to prevent demineralization of teeth.It was found, that only MgCO3 added to PCL can keep pH above 7.4 during enzymatic degradation over 28 days. This ensured that the polymer matrix was 100% degraded without lowering the pH value, which might prevent deminarlization of dental hard tissues for it future intended application. This influence can be directly attributed to the solubility of MgCO3, as all other buffer substances are rinsed out of the PCL matrix too quickly (max. 9 days).

Inorganic/organic composite binder with self-healing property for silicon anode in lithium-ion battery

Silicon (Si) has garnered significant attention as a high-capacity anode material in high-energy density lithium-ion batteries (LIBs). Nevertheless, the huge volume variation of Si (>300%) during cycling results in rapid capacity deterioration, thereby impeding its commercial application. To confront this challenge, inorganic binder has been identified as a highly promising solution for Si anode due to its high bonding strength. Despite its effectiveness, the inorganic binder's limited elasticity hinders the rejuvenation of the impaired electrode structure. Hence, we devised an elasticity and self-healing composite binder, incorporating both inorganic and organic binders. The inorganic lithium metasilicate not only offers ample adhesion sites to Si but also establishes a protective coating layer on SiNPs. Simultaneously, the organic poly (vinyl alcohol) featuring a low glass transition temperature (72 °C) furnishes elasticity and a self-healing framework. Consequently, the Si anode shows exemplary cycling and rate performances. Additionally, the Si||NCM811 full cell attains a reversible capacity of 1.86 mAh/cm2 with a capacity retention of 67% after 50 cycles, indicating the commercial application potential of the composite binder. This study thus explores design strategies for composite binders, paving the way for high-performance Si anode.

Ionic Conductivity of a Lithium-Doped Deep Eutectic Solvent: Glass Formation and Rotation-Translation Coupling.

Deep eutectic solvents with admixed lithium salts are considered as electrolytes in electrochemical devices, such as batteries or supercapacitors. Compared to eutectic mixtures of hydrogen-bond donors and lithium salts, their raw-material costs are significantly lower. Not much is known about glassy freezing and rotational-translation coupling of such systems. Here, we investigate these phenomena by applying dielectric spectroscopy to the widely studied deep eutectic solvent glyceline, to which 1 and 5 mol % LiCl were added. Our study covers a wide temperature range, including a deeply supercooled state. The temperature dependences of the detected dipolar reorientation dynamics and ionic direct current (dc) conductivity reveal the signatures of glassy freezing. In comparison to pure glyceline, the lithium admixture leads to a reduction of ionic conductivity, which is accompanied by a reduction of the rotational dipolar mobility. However, this reduction is much smaller than that for deep eutectic solvents (DESs), where one main component is lithium salt, which we trace back to the lower glass-transition temperatures of lithium-doped DESs. In contrast to pure glyceline, the ionic and dipolar dynamics become increasingly decoupled at low temperatures and obey a fractional Debye-Stokes-Einstein relation, as previously found in other glass-forming liquids. The obtained results demonstrate the relevance of decoupling effects and glass transition to the enhancement of the technically relevant ionic conductivity in such lithium-doped DESs.

생분해성 PLA-나노바이오실리카 복합재 사출성형 최적화

Plant-based biodegradable polylactic acid (PLA) polymers have limited applications, such as in the production of disposable products using the extrusion method. This restricted usability is due to their low glass transition temperature and poor low-temperature molding properties. In the present study, we investigated the changes in PLA polymer properties induced by bioadditives and optimized the conditions of extrusion molding to commercialize biodegradable polymers using an injection molding process. Compared to pure PLA, the constructed PLA composite with nanosilica showed a 15% reduction in melt flow; however, the tensile strength increased by 13%, flexural strength increased by 15.9%, impact strength improved by 18.2%, and hardness increased by 40%, enabling injection molding even at temperatures of 180-190 °C. The mold flow of the nanocomposite and optimization analysis of product injection molding were conducted using a runner and fingate.

Supramolecular polymer-based, ultra-robust, and nonfluorinated, sub-zero temperature self-healing superhydrophobic coatings for energy harvesting

In this study, ultra-robust, nonfluorinated, and sub-zero temperature self-healing superhydrophobic coatings are fabricated by spray-coating imine-bond crosslinked polydimethylsiloxane-based supramolecular polymers (I-PDMS) and SiO2 nanoparticles (NPs). Due to the synergy between I-PDMS binding and SiO2 NPs reinforcement, the resulting I-PDMS/SiO2 coatings can maintain their superhydrophobicity after sandpaper abrasion, sand impacting, hand tapping, and foot trampling and showed the best mechanical robustness among reported superhydrophobic coatings. Furthermore, due to the low glass-transition temperature of I-PDMS monomers and the dynamic nature of the imine bonds, the I-PDMS/SiO2 coatings can spontaneously restore their damaged superhydrophobicity at − 30 °C through the free energy-driven diffusion of I-PDMS monomers. The I-PDMS/SiO2 coatings can be used as friction layers for triboelectric nanogenerators (TENGs), which provide them with long-lasting waterproofing and self-cleaning capabilities, thus preventing their output performance from being degraded due to water infiltration and dust accumulation. Due to the excellent mechanical strength of the I-PDMS/SiO2 coatings, the resulting self-healing superhydrophobic TENGs can generate electrical energy from repetitive motions such as hand tapping or foot trampling, which has not been possible in other reported superhydrophobic TENGs.

High Performance Proprioceptive Fiber Actuators Based on Ag Nanoparticles-Incorporated Hybrid Twisted and Coiled System.

Thermally driven fiber actuators are emerging as promising tools for a range of robotic applications, encompassing soft and wearable robots, muscle function restoration, assistive systems, and physical augmentation. Yet, to realize their full potential in practical applications, several challenges, such as a high operational temperature, incorporation of intrinsic self-sensing capabilities for closed-loop feedback control, and reliance on bulky, intricate actuation systems, must be addressed. Here, an Ag nanoparticles-based twisted and coiled fiber actuator that achieves a high contractile actuation of ≈36% is reported at a considerably low operational temperature of ≈83°C based on a synergistic effect of constituent fiber elements with low glass transition temperatures. The fiber actuator can monitor its contractile actuation in real-time based on the piezoresistive properties inherent to its Ag-based conductive region, demonstrating its proprioceptive sensing capability. By exploiting this capability, the proprioceptive fiber actuator adeptly maintains its intended contractile behavior, even when faced with unplanned external disturbances. To demonstrate the capabilities of the fiber actuator, this study integrates it into a closed-loop feedback-controlled bionic arm as an artificial muscle, offering fresh perspectives on the future development of intelligent wearable devices and soft robotic systems.

Fast-curing bio-based thermoset foams produced via the Michael 1,4-addition using fatty acid-based acetoacetate and acrylate

This study introduces an approach for creating bio-based polymer foams exploiting the Michael reaction that could be utilized as thermal insulation. The thermoset foams were developed using a second-generation bio-based feedstock – tall oil. Tall oil is a by-product of wood pulping in paper manufacturing and mainly comprises unsaturated fatty acids like oleic and linoleic acid. The study explores the use of tall oil-based acetoacetates (Michael donor) combined with various acrylates (Michael acceptor), petrochemical-based (bisphenol-A ethoxylate diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate), and bio-based (epoxidized soybean oil acrylate, epoxidized tall oil free fatty acids-based acrylate), to develop polymer foams that meet today's sustainability requirements. The developed polymer foams underwent extensive characterization. Matrix curing parameters were assessed by measuring changes in dielectric polarization during curing. Foaming parameters, including start and rise times, were precisely measured. The chemical composition of the foams was analysed using Fourier-transform infrared spectroscopy. Their thermal, thermo-mechanical, and mechanical properties were evaluated through thermal gravimetric analysis, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and compression tests. Additionally, the content of closed-cell and the coefficient of thermal conductivity were determined, further characterizing the foams as potential thermal insulation materials. Foams from bio-based donors with petrochemical-based acceptors exhibited a range of enhanced properties. They not only achieved high glass transition temperatures (up to 85 °C by DSC and up to 108 °C by DMA) but also displayed a spectrum of mechanical strengths (compression strength ranging from moderate to as high as ∼ 0.40 MPa) and good thermal isolation properties (thermal conductivity coefficient ∼ 31mW/(m·K)). Bio-based foams, derived from renewable resources, were characterized by properties fitting for flexible foam applications, such as low glass transition temperatures (down to −9.7 °C by DSC and down to 9.8 °C by DMA), reduced compression strength (approximately 0.011 MPa), and increased thermal conductivity (up to 46.7mW/(m·K)), indicating their potential utility in applications where flexibility is a key requirement.

The Effect of Nonterminal Liquid Crystalline Epoxy Resin Structure and Curing Agents on the Glass Transition of Polymer Networks.

Modern science and technology demand a low glass transition temperature, yet one tailored to specific thermoset needs and specific to individual hardener applications. Two novel, nonterminal liquid crystalline epoxy resins (LCER) were synthesised, with their structures characterized via nuclear magnetic resonance (NMR), mass spectrometry (MS), and elemental analysis. Their liquid crystalline nature and thermal properties were determined using polarized optical microscopy (POM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). A set of seven aromatic amines serving as curing agents was used to perform curing in fourteen different systems in order to assess the glass transition temperature (Tg) of the obtained polymer networks using DSC. The liquid crystalline elastomers were obtained with vitrification occurring in a low temperature range (-10-40 °C), with a more predictable outcome for amines with two aromatic rings in the structure than with one. Moreover, the resin with a core consisting of four aromatic rings produces networks with higher Tg than the three-aromatic resin. The use of nonterminal LCER allowed the lowering of the glass transition temperature of the polymers to more than 70 °C compared to a terminal analogue. This brings new possibilities of designing highly elastic yet cured polymers with potential for use in smart applications due to the LC nature of the resin.

The Effects of Microcrystalline Cellulose Addition on the Properties of Wood-PLA Filaments for 3D Printing.

This paper describes the use of microcrystalline cellulose (MCC) as an additive in wood-polylactic acid (PLA) filaments suitable for 3D printing. Filaments prepared with PLA, thermally modified (TM) wood, and three different MCC loadings (1, 3, and 5 wt%) by two-step melt blending in the extruder were characterized with respect to their rheological, thermal, and mechanical response. The analyses demonstrate that a low MCC content (1%) improves the mobility of the polymer chains and contributes to a higher elasticity of the matrix chain, a higher crystallinity, a lower glass transition temperature (by 1.66 °C), and a lower melting temperature (by 1.31 °C) and leads to a higher tensile strength (1.2%) and a higher modulus of elasticity (12.1%). Higher MCC loading hinders the mobility of the polymer matrix and leads to a rearrangement of the crystal lattice structure, resulting in a decrease in crystallinity. Scanning electron micrographs show that the cellulose is well distributed and dispersed in the PLA matrix, with some agglomeration occurring at higher MCC levels. The main objective of this study was to develop and evaluate a filament containing an optimal amount of MCC to improve compatibility between wood and PLA, optimize melt processability, and improve mechanical properties. It can be concluded that a 1% addition of MCC favorably changes the properties of the wood-PLA filaments, while a higher MCC content does not have this effect.

Mechanochromic properties of acridine heterocyclic derivatives with a donor-acceptor configuration

The mechanochromic properties of two acridine heterocyclic derivatives with a donor-acceptor configuration, 10-phenyl-10-(4-(7,7,13,13-tetramethyl-7,13-dihydro-5H-indeno[1,2-b]acridin-5-yl)phenyl)anthracene-9(10H)-one (DpAn-InAc) and 10-(4-(5,5-dimethylbenzofuro[3,2-c]acridin-13(5H)-yl)phenyl)-10-phenylanthracen-9(10H)-one (DpAn-BzAc), were investigated. The effect of different grinding time (10 and 20 min) and pre-heating temperature (−10, 100, and 120 °C) on the mechanochromic performance of DpAn-InAc and DpAn-BzAc were analyzed. The average red shift of the emission peak was 18 nm for DpAn-InAc powder under grinding stimuli, with the long grinding time (20 min) bringing the greatest shift, while both the highest (120 °C) and the lowest (−10 °C) pretreat temperature brought a greater impact on the luminescent peak. On the contrary, the ground DpAn-BzAc preheated at 100 °C showed the maximum wavelength shift, which was ascribed to the lower glass transition temperature of DpAn-BzAc. Meanwhile, the discolored sample could be recovered by ethanol fumigation, proving that the discoloration was reversible. X-ray diffractograms revealed that under the anisotropic force, the microcrystalline structure of DpAn-InAc and DpAn-BzAc were destroyed, resulting in the shift of the fluorescence peak. The fluorescence shift of DpAn-BzAc was more obvious than that of DpAn-InAc, while its recovery was inferior compared to DpAn-InAc, which was due to its looser molecular structure. Finally, DpAn-InAc and DpAn-BzAc were applied in delivering rewritable encrypted information and both of the two molecules have shown capabilities in transmitting coded information. This work sheds light on using the molecule with donor-acceptor molecular structure in the stimuli-responsive field, and shows their potential application in transmitting encrypted information.