Glass Transition Research Articles

A Novel Approach to Fabricate Fe-based Thin Film Metallic Glass With Commercial Boron Carbide and AISI M42 Tool Steel

In this study, we report a Fe-based thin film metallic glass (Fe-Cr-Mo-C-B-X TFMG) fabricated by magnetron sputtering with commercial boron carbide (B4C) target and AISI M42 tool steel pellets. Varied number of M42 pellets were co-sputtered with B4C target, resulting in Fe content ranged from 48.1 at% to 62.8 at%. X-ray diffraction and transmission electron microscopy confirmed that all sample films were amorphous. All samples showed glass transition and crystallization in differential scanning calorimetry (DSC), similar to typical metallic glasses. However, glass transition was barely observable in B4m owing to its high oxygen content. The sample films also had extremely low surface roughness of 0.14 – 0.26 nm. The sample films also showed tribological properties comparable to conventionally deposited TFMG, where the highest hardness and reduced modulus obtained was 9.0 GPa and 150.8 GPa respectively. The sample films also demonstrated specific wear rate K0 as low as 1.6 × 10-5 mm3Nm-1. Our work demonstrates a more cost-effective and sustainable way of fabricating Fe-based TFMG, in which both AISI M42 are readily available and can be easily recycled after use.

Enhanced ionic conductivity of proton-conducting flaxseed gum based biopolymer electrolyte for energy storage

This work presents a facile and systematic way to prepare low resistive proton conducting biopolymer electrolyte (BPE) membranes from flaxseed gum (FG) via the solution casting technique. Ammonium fluoride (NH4F) ionic salt has been added to the FG matrix and optimized the ionic conductivity of the BPE membrane. The structural and morphological investigations were done to comprehend the ion association phenomenon. The enhancement of amorphousity on doping is affirmed by x-ray diffraction (XRD). The complex formation and interactions between FG and proton (H+) have been characterized through fourier transform infrared (FTIR) spectroscopy. The flexibility of the prepared BPE membranes at low glass transition temperature Tg was confirmed by differential scanning calorimetry (DSC) thermal analysis. Electrochemical impedance spectroscopy (EIS) shows maximum ionic conductivity of 4.0 × 10−3 S/cm at FGAF7 composition. The obtained surface topographic images from atomic force microscopy (AFM) confirms that the predominantly uneven amorphous surface with high rms roughness has transformed to a homogenous even surface on the addition of dopant. The TNM findings demonstrated that the ions were the predominant charge carriers. The linear sweep voltammetry (LSV) and cyclic voltammetry (CV) investigations were employed to confirm the electrochemical stability of the BPE membrane. An electrical double layer capacitor (EDLC) has been fabricated using the optimized utmost conducting BPE membrane as an electrolyte and characterized using cyclic voltammetry (CV). These outcomes indicates that the present electrolyte shows promising performance for application in energy storage devices.

Physiochemical profiling of bioplasticizer derived from Ficus benghalensis leaves for eco-friendly applications

Ficus benghalensis is a tree belonging to the Moraceae family, reaching a height of 20–30 m and featuring branches that spread out widely, along with roots that grow in the air. F. benghalensis leaf cellulose (FBLC) is a type of biodegradable plasticizer with a restricted range of uses. Using pyrolysis and chemical reactions, this research aimed to produce a biodegradable plasticizer from natural sources. Once extracted, microscopic investigations evaluated the plasticizer’s suitability for use in lightweight packaging. The prominent Fourier transform infrared peaks ranging from 644 to 1124 cm−1 indicated the presence of C–Cl and C–F bonds. Additionally, the peak at 1524 cm−1 corresponds to the C–OH stretching in FBLC plasticizer, which is an organic molecule. The thin, downward UV peak indicated the presence of lignin or hemicelluloses. A strong transmission peak was observed at wavelengths of 240 and 366.34 nm. The FBLC plasticizers could be responsible for the size variations seen in the XRD view. The presence of a prominent thermogravimetric analysis (TGA) peak at an angle of 2θ = 28.35° indicated that the plasticizers had a significant enhancement on its crystalline properties. The material exhibits thermal stability up to a temperature of 271 °C. The FBLC plasticizer’s kurtosis (Rku) value ranged from 13.44 to 15.74, with a maximum value of 15.74 generating spikes on the produced surface and a minimum value of 13.44 skewing atomic force microscopy data. Scanning electron microscopy analysis revealed the presence of micro-sized fillers, plasticizers particles, rough surfaces on the fillers, and well-matched rough surfaces. The EDX test confirmed that the FBLC was free from any elemental impurities and showed a high level of purity. The Rq or Rrms value of FBLC surface roughness, measured at 48.28 μm, represented the square root of amplitudes relative to the midline. A significant reduction at 71.76 °C demonstrated the main thermal transition of the biopolymer, also known as the glass transition temperature of FBLC. In summary, the research findings suggested that bioplasticizers are a viable substitute for synthetic chemicals commonly used in the lightweight packaging industry.

Low-Melting Maleimide-Containing Phthalonitrile Resins: Synthesis, Curing Behaviour, and Thermal Performance

Phthalonitrile (PN) resins are highly valued in high-performance applications due to their exceptional thermal stability and mechanical properties. However, traditional PN monomers suffer from high melting points and slow curing rates, often requiring external curing accelerators that can compromise thermal performance. This study focuses on the synthesis and characterization of novel low-melting maleimide-containing PN monomers designed to enhance curing efficiency and thermal properties. Maleimide groups were introduced to improve self-catalytic properties, facilitating a more efficient curing process. The polymerization behavior, thermal stability, adhesive, and mechanical properties of these compounds were thoroughly investigated. Differential Scanning Calorimetry (DSC) and rheological tests showed that incorporating alkyl groups significantly improved flow properties, facilitating easier processing. The difference in the three-dimensional network structures of the cured PN resins was confirmed by Fourier Transform Infrared (FT-IR) spectroscopy. Thermogravimetric Analysis (TGA) demonstrated outstanding thermal stability, with 5% weight loss temperatures ranging from 387°C to 418°C under air and from 420°C to 471°C under nitrogen. Dynamic Mechanical Analysis (DMA) confirmed high glass transition temperatures (Tg) exceeding 400°C, indicating superior thermal performance and making these resins suitable for advanced applications in harsh environments. These findings suggest that low-melting maleimide-containing PN systems are promising candidates for high-performance materials in aerospace, electronics, and other demanding fields.

Preparation of cellulose nanofiber/polyvinyl alcohol-based composite films for metal ion detection by starch/disodium calcium ethylenediaminetetraacetate synergistic complexation effect

Heavy metal pollution causes irreversible damage to plants, animals, and humans. Therefore, it is meaningful to develop facile, fast, and efficient strategies for heavy metal ion (HMI) detection. Here, a portable composite film (CPSE) was designed for HMI detection with high sensitivity and wide detection range. The CPSE was prepared by using cellulose nanofibers (CNF)/polyvinyl alcohol (PVA) as the matrix and utilizing modified starch (HPS) to assist disodium calcium ethylenediaminetetraacetate (EDTA-Ca) to form stable complexes with HMI. The R, G and B values (the three primary colors of light) were captured using an image acquisition system to produce an HMI standard color card successfully. Specifically, the composite film can effectively distinguish Cu2+, Pb2+ and Fe3+. The response time of the composite film to HMI was 2–4 s, and the detection ranges of Cu2+ and Fe3+ were 5–700 ppm and 10–1000 ppm, respectively. Additionally, the synergistic effect of HPS and EDTA-Ca led to the increase in tensile strength (1.59–1.71 times), tear strength (3.29–3.57 times), and glass transition temperature (~ 6 °C) compared to CNF/PVA/HPS and CNF/PVA/EDTA-Ca films. This study confirms the value of CPSE films as materials for HMI detection and suggests innovative ideas for designing similar biomass detection materials in the future.

Coamorphous systems of rebamipide: Selection of amino acid coformers based on protein-ligand docking, in vitro assessment and study of interactions by computational and multivariate analysis.

Three coamorphous systems of Rebamipide (REB) with the amino acids namely, Tryptophan (TRP), Phenylalanine (PHE) and Arginine (ARG) are reported. A unique approach for the virtual screening of amino acid coformers is presented by employing molecular docking studies based on interactions of the drug molecule with various amino acid fragments in the drug-receptor cocrystal structure. Successful formation of stable coamorphous systems with ARG, TRP and PHE served as the proof-of-concept along with negative benchmarking standards Histidine and Aspartic acid, wherein coamorphous systems could not be obtained despite multiple trials which resulted in crystalline physical mixtures. The coamorphous systems were characterized by a halo pattern in Powder XRD and a single glass transition temperature (Tg) in modulated DSC. Physical stability assessments of the coamorphous systems showed direct correlation of Tg with the observed stability of the amorphous phase which was found in the order ARGREB > TRPREB ≥ PHEREB. To determine the specific functional groups engaged in the interactions, multivariate analysis was performed on the FTIR spectra. These interactions were further validated by DFT and QTAIM analysis, which revealed key noncovalent interactions in the three coamorphous systems. All three coamorphous systems showed excellent release profiles of the API as demonstrated by the f2 and DE parameters in the order ARGREB ≥ TRPREB > PHEREB ≥ amorphous drug, far exceeding that of the crystalline drug. The interplay of multivariate analysis and QTAIM can be useful in estimating the interactions within the coamorphous systems which can further contribute to stability and physicochemical properties of the systems.

Tunable protic ionic liquid catalysts for the efficient one-step synthesis of isosorbide-based polycarbonates

Using CO2-derived dimethyl carbonate (DMC) instead of diphenyl carbonate (DPC) as a carbonyl source for synthesizing bio-based polycarbonates is a green and cost-effective route. However, the synthesis of high-performance polycarbonates via the DMC route remains challenging due to the poor reactivity and selectivity of DMC compared to DPC. Herein, we designed a series of highly active protic ionic liquid (PIL) catalysts for the synthesis of poly(isosorbide carbonate) (PIC) from DMC with ISB. The influences of the structures of anion and cation on the catalytic activity of PILs were systematically studied. Compared with the reported aprotic IL catalysts, the unique reactive hydrogen of the cation in PILs could form a strong hydrogen bond interaction with the carbonyl group of DMC, resulting in higher reactivity of the carbonyl carbon of DMC. Moreover, the nucleophilicity of the anion could be easily tuned by adjusting the pKa value, which effectively realized the balance of the reactivity difference between exo-OH and endo-OH in ISB. Among them, [DBUH][Im] showed the highest catalytic activity, and the weight-average molecular weight (Mw) and glass transition temperature of PIC reached 55,700 g/mol and 160 °C, respectively. Combined with NMR analyses and DFT calculations, the mechanism that exhibited the synergetic catalytic effect of anion-cation for the polymerization of DMC and ISB was presented.

Microwave-Functionalized Natural Tannic Acid as an Anticorrosive UV-Curable Coating

Corrosion causes serious steel deterioration with consequent negative impacts on the environment and economy. Organic coatings are widely exploited to provide corrosion protection on low-carbon steel. However, the raw materials and preparation methods for common anticorrosive coatings are not sustainable. In this framework, the efficient microwave-assisted methacrylation of a natural polyphenolic compound, tannic acid (TA), provided a UV-curable monomer with a high degree of substitution. The produced methacrylated tannic acid (MTA) was characterized by means of 31P NMR and FTIR spectroscopies. The UV-curing of MTA by radical photopolymerization was deeply investigated via the real-time FTIR, photo-DSC, and photo-rheological analyses, confirming the high photo-reactivity of MTA with a conversion of 80% and a gel point at 2.5 s. The UV-cured MTA showed good thermal stability and a glass transition temperature (Tg) of 133 °C. Furthermore, UV-cured MTA coating exhibited high hardness and hydrophobicity. The zeta potential measurement indicated a negatively charged surface with an isoelectric point (IEP) at pH 2.7. Finally, the good corrosion protection performance of UV-cured MTA coating on plasma pre-treated steel surface was assessed through electrochemical impedance spectroscopy.

Evaluation of aspartame as a co-former in the preparation of co-amorphous formulations of dipyridamole using spray drying

Co-amorphous systems (CAMs) have shown promise in addressing the challenges associated with poorly water-soluble drugs. However, the limited selection of co-formers and the use of lab-scale techniques for their preparation present challenges in fully utilizing the advantages of CAMs. In this study, we used aspartame (a methyl ester of the aspartic acid/phenylalanine) as a model dipeptide with the BCS class II drug dipyridamole, to prepare co-amorphous systems using spray drying. The feed solutions were prepared by dissolving the drug and co-former into methanol–water mixtures. The spray drying process was evaluated and solid-state properties were compared with those of the individual amino acids, amino acid mixtures and aspartame as co-formers. Co-amorphous systems prepared with aspartame (AspPhe) exhibited better solid-state properties, including a higher glass transition temperature (Tg), compared to the individual amino acids and the mixture of amino acids. Additionally, this formulation showed improved physical stability when stored at 25 °C/60 % RH conditions. Hirshfeld Surface (HS) analysis was employed to visualize and analyse the molecular interaction sites within the crystal structures of dipyridamole and aspartame. The observed interactions were then correlated with the molecular interactions identified through FT-IR spectroscopic analysis within the CAMs. The spectroscopic analysis revealed molecular interactions between the sites found at the shortest distances in the HS analysis. The dominant hydrogen bond interactions identified in the co-amorphous DPM-AspPhe system was found to contribute significantly to its improve stability. X-ray powder diffraction in non-ambient mode reveals that both temperature and humidity play a role in the crystallization of the co-amorphous DPM-AspPhe. Crystallization rates increased notably at high temperature and humidity. To predict stability under accelerated conditions, the crystallization rates from DPM-AspPhe were fitted to a modified Arrhenius equation. However, the predictive accuracy of the resulting model was limited to a specific range of conditions.

Wave-transparent and eco-friendly flame-retardant phosphorus-based phthalonitrile/quartz composites by a synchronized self-curing strategy with cyano and alkynyl groups

The robust human–machine interaction systems of the aerospace industry necessitate the development of thermal resistant wave-transparent composites, with a pivotal focus on organic resin matrix. However, enhancing the heat resistance of such materials while preserving other critical attributes has been a formidable challenge. In this study, a novel designed strategy of a dual-curing functional phosphorus-based phthalonitrile monomer (P-ALK-PN) has been proposed. The optimized curing temperatures for intra- or intermolecular Diels-Alder reactions of alkynyl groups and polyaddition reaction of cyano groups resulted in a homogeneous and highly crosslinked N-enriched phthalonitrile system. After curing at 450 °C, the resin, namely P-ALK-PN-450 °C, demonstrated exceptional thermal stability (T5% = 644 °C), thermo-oxidative stability (T5% = 554 °C), and char yield at 800 °C (90.7 % in N2 and 67.5 % in air). Their quartz fiber reinforced composites (P-ALK-PN/QFs) were subsequently fabricated by the hot-pressing process. Upon post-curing at 420 °C, P-ALK-PN-420 °C/QF displayed elevated glass transition temperature (550 °C), flexural strength (319 MPa), and relatively low dielectric properties with a dielectric constant (Dk) of approximately 4.2 and a dissipation factor (Df) less than 0.02 across a wide temperature ranging from 25 °C to 600 °C. Especially, it exhibited excellent flame retardancy (only a 6.7 % weight loss at ambient temperatures exceeding 1300 °C for 200 s) as well, stemming from release of eco-friendly inert gases (NH3) and formation of a graphitized protective layer during pyrolysis. These promising results highlight the potential applications of P-ALK-PN resins in aerospace and high-performance engineering fields.

A Bio-Based Polybenzoxazine Derived from Diphenolic Acid with Intrinsic Flame Retardancy, High Glass Transition Temperature and Dielectric Properties.

A bio-based benzoxazine monomer, diphenolic methyl ester hexafluoro diamino benzoxazine (DPME-HFBz), was successfully synthesized from diphenolic acid (DPA), and the chemical structure was successfully verified. The curing kinetics were studied via non-isothermal differential scanning calorimetry (DSC). The activation energies of DPME-HFBz were calculated by Kissinger and Ozawa methods to be 136.15 and 139.92 kJ/mol, respectively, and the reaction order was calculated to be first order. Owing to the large number of hydrogen bonds after polymerization, poly(DPME-HFBz) presented an ultra-high glass transition temperature of 312 °C and a high initial decomposition temperature (350 °C under air and 345 °C under nitrogen). Because of the excellent charring ability (50.2% residue under nitrogen), the LOI value of poly(DPME-HFBz) was as high as 38%. Poly(DPME-HFBz) also exhibited a very low heat release capacity (HRC) of 90 J/(g·K). In addition, poly(DPME-HFBz) had a dielectric constant (Dk) of 1.88 at 1.5 MHz, which was much lower than the Dk of the reported low-dielectric polymers. This work provides an efficient and sustainable strategy for the synthesis of benzoxazine thermosetting materials with excellent comprehensive properties.

Effects of Al Substitution for Fe in Na₅FeSi₄O₁₂ (5.1.8) Glasses: Structure and Crystallization

In this study, the effects of substituting Al for Fe in 5Na2O∙(Al2O3)x∙(Fe2O3)1-x∙8SiO2 glass, x=0 to 1, and Na5AlxFe1-xSi4O12 (5.1.8) crystal, were investigated using thermal analysis, Fe K-edge X-ray absorption, X-ray diffraction, Raman spectroscopy, and Electron Probe Microanalysis. In both glass and crystallized glass, nearly all the Fe was tetrahedrally coordinated Fe3+, as expected from the high concentration of Na2O. The substitution of Al for Fe in the glasses caused the glass transition temperature to increase as polymerization increased, as evidenced by Raman, likely due to both field strength differences of Al vs Fe and a small amount of Fe2+ network modifier present with Fe. After heat treatment at 700 °C for 24 hours, the glasses had crystallized, forming Na2SiO3 and NaAlSiO4 in compositions with high Al concentrations and the 5.1.8 crystal in compositions with high Fe concentrations. Through electron microprobe, it was determined that <0.04 formula unit Al incorporated into the 5.1.8 crystal, i.e. Na5Fe0.96Al0.04Si4O12. The 5.1.8 crystal only formed when Fe concentration was higher than Al in the starting glass.

Feasible estimation of weathering stability for free film acrylic coatings via dynamic mechanical analysis as the sole characterization method

AbstractWeathering stability is a highly relevant materials property, especially for exterior coatings. Assessment of artificially or naturally weathered coatings is however still mostly subjective without distinct correlation between the formulation of a coating and its weathering stability. An aggravating issue in the industrial context is the often very sparse information on the exact chemical composition of materials by the manufacturers. In this study, a quantitative method to examine weathering-induced changes in coatings with limited chemical information is described, which is based solely on dynamic mechanical analysis (DMA). This approach is applied to free films to eliminate possible influences of the substrate during the measurement. The effects of artificial weathering on three exemplary acrylic waterborne wood coatings are then examined and compared to the results of state of the art artificial weathering. Precisely, the impact of additional light stabilizer on mechanical properties, molecular weight, and Tg is monitored. For the exemplary systems, it could be shown that the molecular weight of the polymers decreases during artificial weathering, where the most prominent decrease was observed in the first 300 h. In the same time frame, E′ and E″ also decrease, while the glass transition temperature increased dependent of the formulation by 6–15°C. Remarkably, for coatings without light stabilizer an apparent two-staged degradation mechanism is observed, which leads to an increase of E′ and E″ after 600 h of artificial weathering, accompanied with an increased brittleness of the free film. The primary goal of this approach is to offer a tool for quick and systematic investigation of new coating formulations in the industrial context.

Tungsten-Doped Borosilicate Glasses for Radiation Shielding

In this study, a series of glasses in the 25 Na2O- 15 B2O3- (60-x)SiO2- xWO3 system (with x up to 2 mol%) was developed by a melt-quench route. To evaluate their potential applications as novel lead-free transparent shielding materials in nuclear medicine, the impact of tungsten trioxide (WO3) addition on glass formation, structure, properties, and radiation shielding effectiveness of the produced glasses was also investigated. The glass forming ability was found to be restricted, and high-transparency homogeneous bulk glasses containing WO3 up to 1.5 mol% could only be achieved, as verified by XRD measurements. FTIR spectroscopy revealed the network modifications caused by the incorporation of various WO3 concentrations into the glass system. This was further supported by thermal and mechanical investigation, which demonstrated that increasing WO3 content increased both glass transition temperature (Tg) and Vickers hardness (Hv) values. The increases in Tg and Hv could be attributed to tungsten's participation in the formation of new strong W-O connections. Furthermore, the radiation shielding performance of the glasses, such as the half-value layer (HVL), the mean free path (MFP) and the lead equivalent thickness (LEV), as determined by means of a NaI(Tl) scintillation detector in a narrow beam geometry setup using 137Cs, 133Ba and 57Co as the radiation sources, were compared to that of commercial lead glass and found to be improved with higher WO3 content. The findings provide sufficient data to indicate that our tungsten-doped borosilicate glasses, especially the sample containing 1.5 mol% WO3, could be potential candidates for alternative lead-free, high-transparency radiation shielding materials in nuclear medicine applications.

Medium-Range Structural Order as the Driver of Activated Dynamics and Complexity Reduction in Glass-Forming Liquids.

We analyze in depth the Elastically Collective Nonlinear Langevin Equation theory of activated dynamics in metastable liquids to establish that the predicted inter-relationships between the alpha relaxation time, local cage and collective elastic barriers, dynamic localization length, and shear modulus are causally related within the theory to the medium range order (MRO) static correlation length. The latter grows exponentially with density for metastable hard sphere fluids and as a nonuniversal inverse power law with temperature for supercooled liquids under isobaric conditions. The physical origin of predicted connections between the alpha time and other metrics of cage order and the thermodynamic inverse dimensionless compressibility is fully established. It is discovered that although kinetic constraints from the real space first coordination shell are important for the alpha time, they are of secondary importance compared to the consequences of the more universal MRO correlations in both the modestly and deeply metastable regimes. This understanding sheds new light on the theoretical basis for, and prior successes of, the predictive mapping of chemically complex thermal liquids to effective hard sphere fluids based on matching their dimensionless compressibilities, a scheme we call "complexity reduction". In essence, the latter is equivalent to the physical requirement that the thermal liquid MRO correlation equals that of its effective hard sphere analog. The mapping alone is shown to provide a remarkable level of quantitative predictive power for the glass transition temperature Tg of 21 molecular and polymer liquids. Predictions for the chemically specific absolute magnitude and growth with cooling of the MRO correlation length are obtained and lie in the window of 2-6 nm at Tg. Dynamic heterogeneity, elastic facilitation, and beyond pair structure issues are briefly discussed. Future opportunities to theoretically analyze the equilibrated deep glass regime are outlined.

The effect of single walled carbon nanotubes on conductivity and thermal properties of glass fiber reinforced composites

Abstract This paper reports on a comprehensive study of the effect of single-walled carbon nanotube (SWCNT) on the alternating current (AC) conductivity, thermal and morphological properties of the unsaturated polyester based glass fiber reinforced polymer composite (GFRPC). AC conductivity measurements were carried out using the impedance spectrum and thermal measurements were carried out using differential scanning calorimetry (DSC) at a temperature range of 24-900 °C and heating rates of 20 °C/min. Impedance results showed that the conductivity behavior in the nanotube-loaded composite laminate obeys a Jonscher-type mechanism. At low frequencies, the conductivity value remains almost constant for the doped material and takes the value of 10-5 S/cm. It is observed that the AC conductivity starts to increase after the critical frequency value of approximately 103 Hz and increases up to 10-2 S/cm due to hopping and tunneling mechanisms caused by space charge polarization accumulated in the local regions at high frequencies. The pure material with an insulating nature also exhibited a typical insulating behavior. Thermal testing showed that nanotube reinforcement increases thermal conductivity in three different directions. DSC thermocurves analysis also revealed that the addition of carbon nanotubes increased the glass transition temperature of the material from 180°C to 190°C. The scaling and fractal analysis methods were also applied to obtain hetero morphological structure of materials. The fractal analysis results indicated that carbon nanotube doping to the standard sample increases the coating rates, scalability and heterogeneity of the solid phase surface of the sample. The coating rates of composite surfaces were calculated as 45% and 36%, respectively. Morphology analysis revealed that the probability of finding surface particles for the nanotube-doped sample decreased compared to the undoped sample, but the fractal dimension value increased. While this value was 1.83 in the pure sample, it increased to 1.92 in the nanotube material.

Synthesis of lignin-based elastomers via ARGET ATRP: Exceptional mechanical strength, adhesion, and self-repair properties.

In this study, ARGET ATRP method was employed to graft two functional monomers from lignin, resulting in the synthesis of a series of Lignin-graft-poly(lauryl methacrylate-co-cyclohexyl methacrylate) (Lignin-g-P(LMA-co-CMA)) copolymers with varying feed ratios and lignin content. The results demonstrate that by varying the feed ratios of the two monomers, the glass transition temperature of lignin-based elastomers can be finely tuned. Importantly, the introduction of lignin and CMA imparts outstanding mechanical properties to the lignin-based elastomers, with a maximum tensile strength reaching 20.13 MPa. The elastic recovery rate of the lignin-based elastomers was exceptional, with the elastic recovery coefficient (ER) of Lignin0.52-PLMA500 exceeding 90 %. Adhesion tests on various substrates revealed the remarkable adhesion properties of these copolymers. In particular, Lignin0.52-PLMA500 exhibited strong adhesion on both iron plate and glass substrate, with adhesion strengths of 2.23 MPa and 2.33 MPa, respectively. Notably, Lignin0.52-PLMA500 demonstrated significant self-healing ability after damage. Furthermore, the lignin-based elastomer exhibited exceptional ultraviolet absorption performance. In conclusion, the incorporation of lignin opens up a novel pathway for the development of high-strength and tough lignin-based elastomers. However，more effort still needs to be paid for increasing the adhesive properties aiming to explore more potential application field.

Enantiomorphic Site-Assisted Chain End Control Stereospecific Alternating Copolymerization of Chiral Cyclic Diesters.

Stereospecific alternating copolymerization of different chiral cyclic esters is one feasible approach to enrich the structural diversity of copolyesters and tailor their properties. However, dramatically different reactivities of different cyclic esters let a perfectly stereospecific alternating polymerization of these cyclic esters be a challenge, thus the catalyst is required to balance their reactivities. Herein, a remarkable enantiomorphic site effect on chain end control was discovered and successfully utilized to balance the reactivities of highly reactive S, S-lactide (S, S-LA) and low reactive R, R-ethylglycolide (R, R-EG)/R, R-propylglycolide (R, R-PG) during their heterospecific alternating copolymerization. The enantiomorphic site of R, R-SalenAl complex can increase the relative reactivity of R, R-EG/R, R-PG and suppress that of S, S-LA, then a perfectly alternating sequence of the copolymer of S, S-LA and R, R-EG/R, R-PG can be achieved (Palt=0.96/0.91); inversely, using S, S-SalenAl complex, the significant enantiomorphic site effect enlarges the reactivity difference of two monomers, the alternating level was just 0.70/0.68 even to 0.61. Poly(S, S-LA-alt-R, R-EG) with a high alternating regularity exhibits lower glass transition temperatures and a dramatically higher elongation at break (ϵB=449±51 % (Palt=0.96) vs ϵB=6±1% (Palt=0.70)).

Enantiomorphic Site‐Assisted Chain End Control Stereospecific Alternating Copolymerization of Chiral Cyclic Diesters

AbstractStereospecific alternating copolymerization of different chiral cyclic esters is one feasible approach to enrich the structural diversity of copolyesters and tailor their properties. However, dramatically different reactivities of different cyclic esters let a perfectly stereospecific alternating polymerization of these cyclic esters be a challenge, thus the catalyst is required to balance their reactivities. Herein, a remarkable enantiomorphic site effect on chain end control was discovered and successfully utilized to balance the reactivities of highly reactive S, S‐lactide (S, S‐LA) and low reactive R, R‐ethylglycolide (R, R‐EG)/R, R‐propylglycolide (R, R‐PG) during their heterospecific alternating copolymerization. The enantiomorphic site of R, R‐SalenAl complex can increase the relative reactivity of R, R‐EG/R, R‐PG and suppress that of S, S‐LA, then a perfectly alternating sequence of the copolymer of S, S‐LA and R, R‐EG/R, R‐PG can be achieved (Palt=0.96/0.91); inversely, using S, S‐SalenAl complex, the significant enantiomorphic site effect enlarges the reactivity difference of two monomers, the alternating level was just 0.70/0.68 even to 0.61. Poly(S, S‐LA‐alt‐R, R‐EG) with a high alternating regularity exhibits lower glass transition temperatures and a dramatically higher elongation at break (ϵB=449±51 % (Palt=0.96) vs ϵB=6±1% (Palt=0.70)).

Physical Adsorption and Glass Transition of Thin Polystyrene Films at a Graphene Interface

Physical Adsorption and Glass Transition of Thin Polystyrene Films at a Graphene Interface