Formation Of Cross-links Research Articles

Inhibition of cross-linked lysinoalanine formation in pH12.5-shifted silkworm pupa protein, and functionality thereof: Effect of ultrasonication and glycation

We added three different carbohydrates (Xylose/Xyl, Maltose/Mal, and Sodium alginate/Sal) to pH12.5-shifted silkworm pupa protein isolates (SPPI), and examined the influence of multi-frequency ultrasound (US) on them, with reference to lysinoalanine (LAL) formation, changes in conformational characteristics and functionality. Results showed that, the LAL content of the glycoconjugates - SPPI-Xyl, SPPI-Mal, and SPPI-Sal decreased by 1.47, 1.39, and 1.54 times, respectively, compared with the control. Notably, ultrasonication further reduced the LAL content by 45.85 % and brought SPPI-Xyl highest graft degree (57.14 %). SPPI-Xyl and SPPI-Mal were polymerized by different non-covalent bonds, and SPPI-Sal were polymerized through ionic, hydrogen, and disulfide (covalent/non-covalent) bonds. Significant increase in turbidity, Maillard reaction products and the formation of new hydroxyl groups was detected in grafted SPPI (p < 0.05). US and glycation altered the structure and surface topography of SPPI, in which sugars with high molecular weight were more likely to aggregate with SPPI into enormous nanoparticles with high steric hindrance. Compared to control, the solubility at pH 7.0, emulsifying capacity and stability, and foaming capacity of SPPI-US-Xyl were respectively increased by 244.33 %, 86.5 %, 414.67 %, and 31.58 %. Thus, combined US and xylose-glycation could be an effective approach for minimizing LAL content and optimizing functionality of SPPI.

Development of cat-GRRM/MC/MD method for the simulation of cross-linked network structure formation with molecular autocatalysis

Epoxy resins, which are common matrices in carbon fibre-reinforced plastics, are derived from the curing of epoxy amines. Molecular dynamics (MD) simulations are commonly used to model the physical properties of such network polymers, but they do not account for chemical reactions. Quantum chemical (QC) calculations can elucidate reaction mechanisms and energies but are not suitable for models with thousands of atoms. To address these limitations, in this study, we developed a new method, cat-GRRM/MC/MD, that combines QC calculations in the Global Reaction Route Mapping (GRRM) program with reaction simulations involved in MD simulation methods. This approach allows the simulation of reaction pathways in which proton donor molecules such as alcohols and amines act as molecular catalysts (autocatalysis), and the reaction kinetics are realised in a Monte Carlo (MC) manner. Our results show that autocatalysis significantly reduces the activation energy of the epoxy resin reaction, bringing the calculated data closer to the experimental results. When these quantum chemical calculations were incorporated into MD simulations, it was found that the activation energy influenced the crosslinking results. Models including catalysis led to network polymers with larger carbon skeletons, and physical properties such as the Young's modulus and glass transition temperature become closer to experimental results. This study not only deepens our understanding of the mechanism of the self-catalytic reaction of epoxy resins but also provides a new tool for accurately simulating the performance of epoxy resins, thus enabling more precise control of their properties.

Trimethoxy Silyl End-Capped Hyperbranched Polyglycidol/Polycaprolactone Particle Gels for Cell Delivery and Tissue Repair: Mechanical Properties, Biocompatibility, and Biodegradability Studies

This study focuses on the development of new biocompatible and biodegradable particle gel scaffolds based on PCL-HBPG/1SiHBPG triblock copolymers composed of a polycaprolactone (PCL) core and two outer blocks of trimethoxysilyl end-capped hyperbranched polyglycidol (HBPG/1SiHBPG) that have the potential to be used in soft tissue regeneration. The relationship between the gel’s composition, structure, mechanical properties, and performance has been investigated for the first time and the copolymer design parameters have been optimized. The particle gel scaffolds were formed from the concentrated dispersions of the most hydrophobic PCL-45HBPG/1SiHBPG at low temperatures, and were the result of the numerous hydrogen bonds formed from the HBPG/1SiHBPG moieties as well as the formation of siloxane crosslinks (i.e., Si–O–Si bonds). These gels were formed in the physiological temperature range. Gels with a mechanical strength that gradually increases were formed from the physically crosslinked PCL-45HBPG/1SiHBPG particles effectively and safely, in the absence of UV radiation. They feature high elasticity and undergo enzyme-triggered disassembly. The gels are biocompatible and have the potential to invoke cell attachment and differentiation in the absence of exogenous biological stimuli. A successful outcome of this study will be the prospect of a new approach for tissue regeneration that is currently not available.

The impact of ice slurry as a medium on oxidation status and flesh quality of shrimp (Litopenaeus vannamei) during refrigeration storage.

Oxidation of lipid and protein is a major reason of flesh quality deterioration during storage. In this work, cold storage (CS) and flake ice (FI) storage, as traditional strategies for live shrimp (Litopenaeus vannamei) sedation and refrigerated storage, showed remarkable oxidation damage of lipid and protein in shrimp flesh during storage. In contrast, ice slurry (IS), with good heat exchange capacity and contactability, stunned shrimp in a sudden and thus relieved antemortem stress, which resulted in reducing the reactive oxygen species and reactive nitrogen species accumulation, and the oxidation damage risk in flesh. Additionally, IS, as a storage medium acted an oxygen barrier, further inhibited the oxidation of lipid and myofibrillar protein (MP), as revealed by the lower thiobarbituric acid reactive substances level, carbonyl (CO) derives content, total disulfide bond (S-S) content, and the higher total sulfhydryl (SH) content in shrimp flesh during storage, compared with CS and FI. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis electrophoretogram pattern of MP also suggested better preservation of myosin heavy chain, myosin light chain, actin, and tropomyosin in IS, whereas these proteins degraded in CS and FI. Consequently, IS prevented the formation of cross-linking caused by oxidation in MP, leading to improved shrimp flesh quality during refrigerated storage, as demonstrated by the better maintained hardness, springiness, and water-holding capacity compared to CS and FI.

A Dual Reversible Cross-Linked Hydrogel with Enhanced Mechanical Property and Capable of Proangiogenic and Osteogenic Activities for Bone Defect Repair.

The clinical treatment of bone defects presents ongoing challenges. One promising approach is bone tissue engineering (BTE), wherein hydrogels have garnered significant attention. However, the application of hydrogels in BTE is severely limited due to their poor mechanical properties, as well as their inferior proangiogenic and osteogenic activities. To address these limitations, our develop a dual cross-linked alendronate (ALN)-Ca2+ /Mg2+ -doped sulfated hyaluronic acid (SHA@CM) hydrogel, using a one-step mixing injection molding method known as "three-in-one" approach. This approach enabled the simultaneous formation of Schiff-Base crosslinking and electric attraction-based crosslinking within the hydrogel. The Schiff-Base crosslinking contributed to the majority of the hydrogel's mechanical strength, while the electric attraction-based crosslinking served as a release reservoir for Ca2+ /Mg2+ and ALN, promoting enhanced osteogenic activities and providing additional mechanical reinforcement to the hydrogel. These experimental data demonstrates several favorable properties of the SHA@CM hydrogel, including satisfactory injectability, rapid gelation, self-healing capacity, and excellent cytocompatibility. Moreover, the presence of sulfated groups and Mg2+ within the SHA@CM hydrogel exhibited pro-angiogenic effects, while the controlled release of nanoparticles formed by Ca2+ /Mg2+ and ALN further enhanced the osteogenesis of the hydrogel. Overall, these results indicate that the SHA@CM hydrogel holds significant potential for the clinical translation of BTE.

Potential of carboxymethyl cellulose solution to increase the shale stability

Slope failures in Bangladesh's Chittagong division are a growing concern, with fatalities increasing from 19 in 2000 to 162 in 2017 and projected to rise further. This study aims to identify the most vulnerable rock formation and assess Carboxymethyl Cellulose (CMC) as a solution for enhancing shale strength and mitigating slope failures. The research began by evaluating weathering susceptibility and stability of different rock layers, revealing the high instability of shale in the Bhuban Formation. Slake durability tests measured cation concentration to understand shale instability mechanisms. Laboratory experiments, including immersion tests and grained-and-molded shale specimens, examined CMC's potential to improve shale stability. Results indicated that the shale of the Bhuban Formation had the highest hammer value variations, indicating increased weathering susceptibility. Shale instability was attributed to illite layer dissolution, releasing K+. Intact shale specimens treated with CMC showed enhanced penetration resistance, shear strength, and deformation behavior, suggesting CMC's potential in increasing shale stability. Grained-and-molded shale specimens treated with CMC demonstrated increased shear strength, critical shear displacement, and contraction deformational behavior. Optical microscopy and scanning electron microscopy revealed the formation of cross-links between shale grains, contributing to improved shale stability. Further research is needed to explore the application of CMC for enhancing in situ rock slope stability. This study emphasizes the importance of addressing slope failures in the Chittagong division and provides insights into mitigating the risks through CMC-based interventions.

Characterization of enzyme-crosslinked albumin hydrogel for cell encapsulation

Albumin is an attractive component for the development of biomaterials applied as biomedical implants, including drug carriers and tissue engineering scaffolds, because of its high biocompatibility and low immunogenicity. Additionally, albumin-based gelators facilitate cross-linking reactions under mild conditions, which maintains the high viability of encapsulated living cells. In this study, we synthesized albumin derivatives to undergo gelation under physiological conditions via the peroxidase-catalyzed formation of cross-links. Albumin was modified with phenolic hydroxyl groups (Alb-Ph-OH) using carbodiimide chemistry, and the effect of degree of substitution on gelation was investigated. Various properties of the Alb-Ph-OH hydrogels, namely the gelation time, swelling ratio, pore size, storage modulus, and enzymatic degradability, were easily controlled by adjusting the degree of substitution and the polymer concentration. Moreover, the viability of cells encapsulated within the Alb-Ph-OH hydrogel was high. These results demonstrate the potential applicability of Alb-Ph-OH hydrogels as cell-encapsulating materials for biomedical applications, including tissue engineering.

Characterizing lysinoalanine crosslinks in food systems: Discovery of a diagnostic ion in model peptides using MALDI mass spectrometry.

Formation of lysinoalanine protein-protein crosslinks during food processing adversely impacts nutritional value. However, mapping lysinoalanine directly in food is challenging. We characterized the fragmentation pattern of lysinoalanine crosslinks in synthetic peptide models over a range of pH and time treatments using mass spectrometry. A putative diagnostic ion resulting from the cleavage of the α-carbon and β-carbon of lysinoalanine is identified in MALDI MS/MS spectra. This represents the first step in mapping lysinoalanine in real food samples with higher precision than currently identifiable through standard or customized software. We then determined a correlated trend in the reduction of disulfide bonds and formation of lysinoalanine with increasing pH and time. Mapping lysinoalanine formation is critical to enhance our understanding of molecular processes impacting the nutritional value of foods, including notably in the development of protein alternatives that use alkaline treatment to extract protein isolates.

Dehydrothermal crosslinking of the “Corneoplast”: possibilities of controlling physical, structural and biological properties. Experimental research

Collagen crosslinking – the formation of cross-links between polypeptide chains – reduces the latter’s ability to hydrate. This property is universal for any variant of crosslinking (chemical, physical, physico-chemical) and for any form of collagen (gelatin, fibrillar collagen). Dehydrothermal crosslinking (DTC) is the formation of cross-links in biomaterials when they are heated under vacuum. Despite the fact that DTC methods are widespread in tissue engineering, its effect on the properties of the corneal stroma has not been practically studied. The use of DTK at temperatures up to 200 °C is described. For corneal stroma, the temperature limits of DTC treatment that allow its transplantation are unknown.Purpose: to evaluate the effect of dehydrothermal (DHT) cross-linking of stromal corneal grafts based on the “Corneoplast” material at temperatures of 60, 100, 140, 180 and 220 °C on their principal applicability in keratoplasty.Materials and methods. A corneoscleral disc was excised from a porcine eye (&lt;12 h post-mortem) with epithelium and Descemet’s membrane removed, dried, and a 10 mm central corneal graft was cut out. Dry grafts (n = 36) were divided into 6 groups of 6 samples: in five groups they were kept under vacuum for 3 days at 60, 100, 140, 180, 220 °C; group 6 – untreated control; the structure was evaluated according to small-angle X-ray scattering and atomic force microscopy; for other studies, the grafts were immersed in a phosphate-salt buffer for 24 hours. Parameters evaluated: gross appearance, image quality from 5 m, light transmission, water content, central thickness, suture retention load. A test for epithelialization was performed ex vivo after 3 days in fresh porcine cornea organ culture.Results. The 220 °C mode caused charring destruction of the material. The grafts after 180 °C became significantly weaker than the 9-0 nylon thread. In the range of 60–140 °C suture retention load significantly lowered from 913 (control) down to 137 g (140 °C). Grafts increased their light transmission from 30 (control) up to 75% (140 °C); the central thickness went from 3000 (control) down to 320 um (140 °C), water content decreased from 94 (control) down to 44% (140 °C). Subjective image quality of the grafts after treatment at 60, 100, and 140 °C increased and grafts allowed distinguishing optotypes 0.3, 1.0, and 1.0 decimal, respectively. In organ culture control grafts and grafts after 60 and 100 °C treatment were covered with epithelial cells. 140 °C samples showed smooth surface with no cells upon.Conclusion. The limits of DTC processing are determined. Changing the temperature regime of DTK makes it possible to control the basic properties of “Corneoplast” in a wide range to achieve the possibility of using it as a keratoplastic material.

Substrate-Controlled Catalysis in the Ether Cross-Link-Forming Radical SAM Enzymes.

Darobactin is a heptapeptide antibiotic featuring an ether cross-link and a C-C cross-link, and both cross-links are installed by a radical S-adenosylmethionine (rSAM) enzyme DarE. How a single DarE enzyme affords the two chemically distinct cross-links remains largely obscure. Herein, by mapping the biosynthetic landscape for darobactin-like RiPP (daropeptide), we identified and characterized two novel daropeptides that lack the C-C cross-link present in darobactin and instead are solely composed of ether cross-links. Phylogenetic and mutagenesis analyses reveal that the daropeptide maturases possess intrinsic multifunctionality, catalyzing not only the formation of ether cross-link but also C-C cross-linking and Ser oxidation. Intriguingly, the different chemical outcomes are controlled by the exact substrate motifs. Our work not only provides a roadmap for the discovery of new daropeptide natural products but also offers insights into the regulatory mechanisms that govern these remarkably versatile ether cross-link-forming rSAM enzymes.

Cross-linked gelatin–riboflavin-based film incorporated with essential oils and silver nanoparticle by gamma-irradiation: A novel approach for extending the shelf life of meat

The gamma-irradiation is one of the most acceptable technologies to modify the biopolymer structure by forming a highly energetic electron. The effect of gamma-irradiation for cross-linking of gelatin (G) film in the presence of riboflavin (R) and the physicochemical properties of films were investigated. Different concentrations of R (0.3, 0.75, and 1.2% (w/w) based on the dry weight of G) and 3 doses of gamma-irradiation (5, 10, and 15 kGy) were used. The cross-linked film was incorporated with a mixture of essential oils (EOs) and silver nanoparticles (AgNPs) in order to use as an active packaging for prolonging the shelf life of meat. The results indicated 0.75% R (w/w) and 5 kGy irradiation had a positive effect on the tensile strength, water insolubility, and water barrier properties of the composite G film. Nevertheless, the reduction of film elongation (%), suggests the formation of compact structure and cross-linking through the generation of radicals. The infrared spectroscopy evaluation showed that proper irradiation dosages could produce cross-linking bonds in G film and form a denser network. In vitro and in situ microbial analyses showed that the active film incorporated with EO-AgNPs had antimicrobial activity against most spoilage and pathogenic bacteria and was able to prolong the shelf life of meat by up to 21 days. Therefore, irradiated G-R-EO-AgNP film with good mechanical and antimicrobial properties has the potential to be developed as a biodegradable food packaging material in the food industry.

COMPOSITE MATERIALS BASED ON ALICYCLIC COPOLYIMIDE AND ACRYLIC ACID COPOLYMER WITH ACRYLAMIDE

Progress in polymer materials science is mainly associated with the development of new composite materials, created by the introduction of modifying additives into the matrix polymer which which improve polymer characteristics due to their properties. The purpose of this work is to obtain composite materials with improved thermal and mechanical properties from copolyimide based on dianhydrides of tricyclotetracarboxylic and diphenyloxydtetracarboxylic acids with diaminodiphenyl ether modified by a copolymer of acrylic acid with acrylamide. Results and discussion. Polymer compositions of copolyimides of arylalycyclic structure in combination with acrylic acid copolymer and acrylamide, as well as composite materials (film) based on them, were obtained. It was found that with an increase in the content of the added component from 0.35 to 2.0 wt%, uniformity is maintained in the polymer mixture. The infrared (IR) spectroscopy method shows that during formation of the above polymer mixtures the interaction of functional groups of the polymers under study with the formation of hydrogen bonds, which determine the homogeneity of the mixture. By methods of thermogravimetry and stretching of the sample with a constant deformation rate were used to determine, respectively, the thermal resistance and mechanical properties of the developed composite films. The increase of thermal resistance and strength of the film is explained by the formation of partial intermolecular cross-linking between the components of the mixture and the elasticity of the material – with the plasticizing effect of the additive. Conclusion. Polymer mixtures were obtained and composite films were molded on their basis.

Site-specific crosslinking and assembly of tetrameric β-glucuronidase improve glycyrrhizin hydrolysis.

In this study, eight nonconserved residues with exposed surfaces and flexible conformations of the homotetrameric PGUS (β-glucuronidase from Aspergillus oryzae Li-3) were identified. Single-point mutation into cysteine enabled the thiol-maleimide reaction and site-specific protein assembly using a two-arm polyethylene glycol (PEG)-maleimide crosslinker (Mal2 ). The Mal2 (1k) (with 1 kDa PEG spacer)-crosslinked PGUS assemblies showed low crosslinking efficiency and unimproved thermostability except for G194C-Mal2 (1k). To improve the crosslinking efficiency, a lengthened crosslinker Mal2 (2k) (with 2 kDa PEG spacer) was used to produce PGUS assembly and a highly improved thermostability was achieved with a half-life of 47.2-169.2 min at 70°C, which is 1.04-3.74 times that of wild type PGUS. It is found that the thermostability of PGUS assembly was closely associated with the formation of inter-tetramer assembly and intratetramer crosslinking, rather than the PEGylation of the enzyme. Therefore, the four-arm PEG-maleimide crosslinker Mal4 (2k) (with 2 kDa PEG spacer) was employed to simultaneously increase the inter-tetramer assembly and intratetramer crosslinking, and the resulting PGUS assemblies showed further improved thermostabilities compared with Mal2 (2k)-crosslinked assemblies. Finally, the application of PGUS assemblies with significantly improved thermostability to the bioconversion of GL proved that the PGUS assembly is a strong catalyst for glycyrrhizin (GL) hydrolysis in industrial applications.

Sample size dependence of high-temperature thermal stability of Ti2AlN MAX phase

The thermal stability of Titanium Aluminum Nitride (Ti2AlN) microcrystalline powder in vacuum has been studied by in-situ high-temperature X-ray diffraction. The limit of thermal stability for Ti2AlN phase is T < 850 °C. The process of thermal decomposition consists of the Al atoms sublimation and the formation of a new TiNx phase on the sample surface. An increase in sample size leads to an increase in thermal stability limit (850 °C for microcrystals and 1550 °C for dense bulk sample). Based on crystal chemical analysis and quantum chemical calculations, a mechanism of thermal dissociation was proposed. Kinetics of thermal dissociation of the Ti2AlN phase was modeled using the Avrami equation. Avrami exponent parameters (n = 1.09; 1.28) indicate that the process of germs formation occurs at a subgrain boundaries of the sample. The observed temperature dependence of the parameter n can be associated with a probability change of crosslinking formation during the growth of a new phase. The size dependence of Ti2AlN thermal stability was explained by the ratios of Al diffusion coefficients in the crystallite bulk and along the subgrain boundaries.

THERMAL PROPERTIES OF CROSS-LINKED POLYMERS BASED ON CHITOSAN AND POLYACRYLAMIDE

The thermal properties of cross-linked polymers based on chitosan and polyacrylamide were studied. Samples of the resulting network polymers, which included chains of polyacrylamide and chitosan, were obtained as hydrogel materials by radical polymerization of acrylamide in the presence of chitosan using the redox system of cerium (IV) ammonium nitrate as an initiator and N,N’-methylene-bis-acrylamide as a crosslinker. The structure of the obtained polymers was confirmed by comparing their IR spectra with the spectra of chitosan and polyacrylamide. It was shown that in the IR spectrum of the chitosan-containing sample, the peak at 2932 cm -1 indicates the presence of CH2 groups in the polymer chains and the formation of cross-links. Deformation and valence vibrations of the amide group in polyacrylamide are observed at 1600–1660 cm -1, and the band at 1633 and 1411 cm -1, which appears when the amide bond of polyacrylamide is formed, corresponds to C-N vibrations in the graft copolymer. These characteristic bands confirm the possibility of graft copolymerization of acrylamide on chitosan. The influence of the mass ratio of chitosan and polyacrylamide on the thermal properties of polymer systems was investigated by the method of thermogravimetric and differential thermogravimetric analysis. Atmospheric gas (1 bar, 40 % relative humidity) was used in all thermoanalytical measurements. The samples were examined after vacuum drying at 4 × 10-7 bar and 60 °C using Concentrator Plus. TGA and DTG curves were obtained in the temperature range from 30 to 500 °C with a scanning speed of 5 °C/min using 40 μl aluminum oxide crucibles. It was established that increasing the concentration of chitosan during synthesis reduces the amount of bound water in the obtained samples. Analysis of thermal destruction at the final stages of heating indicates that the presence of chitosan in samples of cross-linked polymers increases their heat resistance by 10–15 °C. The obtained regularities can be used in the creation of composite materials for hydrogel wound dressings and covering medical agents for external use.

Building Porous Ni(Salen)-Based Catalysts from Waste Styrofoam via Autocatalytic Coupling Chemistry for Heterogeneous Oxidation with Molecular Oxygen.

The development of robust and industrially viable catalysts from plastic waste is of great significance, and the facile construction of high performance heterogeneous catalyst systems for phenol-quinone conversions remains a grand challenge. Herein, a feasible strategy is demonstrated to reclaim Styrofoam into hierarchically porous nickel-salen-loaded hypercrosslinked polystyrene (PS@Ni-salen) catalysts with high activities through an unusual autocatalytic coupling route. The salen is immobilized onto PS chain by Friedel-Crafts alkylation of benzyl chloride derivatives, and the generated hydrogen chloride coordinately promotes the simultaneous crosslinking and bridge formation between aromatic rings via a Scholl coupling route, leading to hierarchically porous networks. After the metallization with Ni, the resultant networks exhibit high catalytic activity for the oxidation of 2,3,6-trimethylphenol to 2,3,5-trimethyl-1,4-benzoquinone under mild conditions (303 K, 1bar of O2 ). This catalyst also demonstrates attractive recycling performance without an obvious loss of catalytic efficiency over five consecutive cycles. This methodology might provide a potential sustainable alternative to construct environmentally benign and cost-effective catalysts for specific organic transformation.

Recent advances in the development of the physically crosslinked hydrogels and their biomedical applications

Hydrogels are three-dimensional networks formulated from natural or synthetic polymers with a high capacity to absorb and transport water in their structure. Hydrogels are prepared from the crosslinking of their polymeric chains, which involves two basic mechanisms: chemical crosslinking and physical crosslinking. In chemical crosslinking, hydrogels are held together by covalent bonds; while physically cross-linked hydrogels are produced by non-covalent interactions, such as hydrogen bonds, electrostatic interactions, and hydrophobic forces, among others. Physically cross-linked hydrogels are more similar to biological systems due to their assembly dynamics, so they have wide biomedical applications. The most used approaches in the preparation of hydrogels by physical crosslinking include freeze-thaw, formation of stereocomplexes, ionic interaction, hydrogen bonding, crystallization, and crosslinking by hydrophobic interactions. These approaches are briefly discussed in this review. Some biomedical applications of these hydrogels will also be discussed.

Preparation of UV Debonding Acrylate Adhesives by a Postgrafting Reaction.

UV debonding acrylate adhesive (UDAA) plays a crucial role in the semiconductor industry, where its excellent adhesion is required to ensure the stability of silicon wafers and leave no residue on the surface after UV irradiation. The necessary UV debonding is achieved through the formation of rigid networks by the reactions of all the vinyl groups in the system. Acrylate copolymers with vinyl groups are typically obtained by the grafting reaction of isocyanate with a side-chain hydroxyl comonomer. However, these grafting reactions easily fail due to early cross-link formation. In this study, we illustrate a straightforward method for preparing UDAA by conducting a postgrafting reaction after one-step mixing of isocyanate functional monomer (IPDI-H) and hydroxyl acrylate copolymers (BA-H), thereby skipping the abovementioned vinyl grafting process. The chemical structures of the synthesized IPDI-H and BA-H were confirmed using Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H-NMR) analysis. Gel permeation chromatography (GPC) was employed to determine their molecular weights, while differential scanning calorimetry (DSC) was used to determine their glass transition temperatures. The postgrafting reactions successfully introduced vinyl groups onto the polyacrylate copolymer chains, resulting in high bonding strength during use and a significant decrease in peeling strength after UV irradiation. Rheological methods, including the three-interval thixotropy test (3ITT) and tack test modes, were employed to characterize a series of acrylate UV debonding adhesives. The recovery percentage of the storage modulus in the 3ITT mode indicated that a 0.6 wt% isocyanate curing agent made the UV debonding adhesives resistant to deformation. From the maximum normal force in the tack test mode, it was found that UDAA with 10 wt% PETA monomer and 30 wt% C5 tackifying resin exhibited excellent combined adhesion and debonding properties, which were further confirmed by peel strength tests. Microscope images of the wafer surfaces after removing the adhesive tapes demonstrated the excellent UV debonding properties achieved after 40 s of UV irradiation through the postgrafting reaction. The prepared UDAA has excellent properties; the peel strength can reach 15 N/25 mm before UV irradiation and can be reduced to 0.5 N/25 mm after ultraviolet irradiation. This research establishes a comprehensive method for understanding and applying UDAA in various applications.

Thermomechanical Stress Analysis of Hydrated Vital Gluten with Large Amplitude Oscillatory Shear Rheology.

Vital gluten is increasingly researched as a non-food product for biodegradable materials. During processing, the protein network is confronted with increased thermal and mechanical stress, altering the network characteristics. With the prospect of using the protein for materials beyond food, it is important to understand the mechanical properties at various processing temperatures. To achieve this, the study investigates hydrated vital gluten under thermomechanical stress based on large amplitude oscillatory shear (LAOS) rheology. LAOS rheology was conducted at increasing shear strains (0.01-100%), various frequencies (5-20 rad/s) and temperatures of 25, 45, 55, 65, 70 and 85 °C. With elevating temperatures up to 55 °C, the linear viscoelastic moduli decrease, indicating material softening. Then, protein polymerization and the formation of new cross-links due to thermal denaturation cause more network connectivity, resulting in significantly higher elastic moduli. Beyond the linear viscoelastic regime, the strain-stiffening ratio rises disproportionately. This effect becomes even more evident at higher temperatures. Lacking a viscous contribution, the highly elastic but also stiff network shows less mechanical resilience. Additionally, at these elevated temperatures, structural changes during the protein's denaturation and network shrinkage due to water evaporation could be visualized with confocal laser scanning microscopy (CLSM).

Thermal decomposition behaviors and degradation kinetics of biobased polyesters with partial crosslinking to eliminate cyclic compounds

A series of poly(butylene adipate-co-butylene itaconate) (PBAPI) copolyesters with and without a small amount of ethylenediaminetetraacetic acid (EDTA) were synthesized via melt polymerization. Thermogravimetric analysis -gas chromatography/mass spectroscopy (TGA-GC/MS) techniques were used to identify the thermal degradation behaviors. By introducing 0.1 mol % EDTA into BA/BI = 10/0, the dominant degradation product was converted from furan and cyclopentanone derivatives to CO2 and formation of cyclic compounds was notably inhibited. Moreover, similar tendencies were observed when the BI content increased, demonstrating that the existence ratio of CO2 and furan derivatives increased while the concentrations of cyclopentanone and cyclic compounds reduced during decomposition. Finally, no cyclic compound product was detected in the BA/BI = 7/3 copolyester. These results indicate that the introduction of both EDTA and BI inhibits generation of cyclic compounds, which are attributed to the formation of partial crosslinking for chemical structures. The nonisothermal degradation kinetic was also carried out to investigate the decomposition behaviors. The activation energy requirements at each degradation stage varied with the composition of BA/BI ratios and the introduction of EDTA, demonstrating further evidence of degradation behavior transformation.