Effect Of Different Crosslinkers Research Articles

Water-in-oil microemulsions with greener oil solvents as sustainable nanoreactors of biopolymer nanoparticles

Microemulsions have been widely used in multidisciplinary fields, yet reverse water-in-oil microemulsions are traditionally dispersed in petroleum-based oil solvents. For greener approaches, it should be also feasible to use less toxic, bio-based hydrocarbon solvents as continuous oil phase. Herein, reverse microemulsions in different alkanes, middle-chain alkanols, middle-chain esters or combinations of nonpolar solvent with alkanol are compared, using Aerosol-OT as common surfactant. As model of bio-based solvents, ethyl caprylate, isoamyl acetate and isoamyl alcohol are proposed as a more sustainable approach of oil solvents. Various characterization techniques were used to compare the properties and stability of reverse microemulsions for the different oil phase compositions, ranging from ternary phase diagrams to conductometry and turbidity titrations, micro-Differential Scanning Calorimetry and cryo-Scanning Electron Microscopy. As sustainable application, these microemulsions in bio-based solvents were proved suitable as template phase for the synthesis of cross-linked chitosan nanoparticles. The sizes of the resulting biopolymer nanoparticles were characterized by Dynamic Light Scattering and Atomic Force Microscopy, so that the effect of different crosslinkers and different the oil phase compositions was also compared. Thus, the use bio-based alkyl esters can provide similar microemulsion properties as the conventional alkanes, especially when using a combination of nonpolar solvents with alkanols.

Effect of Different Crosslinkers on Denatured Dentin Collagen's Biostability, MMP Inhibition and Mechanical Properties.

Sound, natural dentin collagen can be stabilized against enzymatic degradation through exogenous crosslinking treatment for durable bonding; however, the effect on denatured dentin (DD) collagen is unknown. Hence, the ability of different crosslinkers to enhance/restore the properties of DD collagen was assessed. Demineralized natural and DD collagen films (7 mm × 7 mm × 7 µm) and beams (0.8 mm × 0.8 mm × 7 mm) were prepared. DD collagen was experimentally produced by heat or acid exposure, which was then assessed by various techniques. All specimens were then treated with 1 wt% of chemical crosslinker 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/n-hydroxysuccinimide (EDC/NHS) and two structurally different flavonoids-theaflavins (TF) from black tea and type-A proanthocyanidins from cranberry juice (CR) for either 30 s or 1 h. The controls were untreated. Dentin films were assessed for chemical interaction and cross-linking effect by FTIR, biostability against exogenous collagenase by weight loss (WL) and hydroxyproline release (HYP), and endogenous matrix metalloproteinases (MMPs) activity by confocal laser microscopy. Dentin beams were evaluated for tensile properties. Data were analyzed using ANOVA and Tukey's test (α = 0.05). Compared with natural collagen, DD collagen showed pronounced structural changes, altered biostability and decreased mechanical properties, which were then improved to various degrees that were dependent on the crosslinkers used, with EDC/NHS being the least effective. Surprisingly, the well-known MMP inhibitor EDC/NHS showed negligible effect on or even increased MMP activity in DD collagen. As compared with control, cross-linking induced by TF and CR significantly increased collagen biostability (reduced WL and HYP release, p < 0.05), MMP inhibition (p < 0.001) and mechanical properties (p < 0.05), regardless of denaturation. DD collagen cannot or can only minimally be stabilized via EDC/NHS crosslinking; however, the challenging substrate of DD collagen can be enhanced or restored using the promising flavonoids TF and CR.

Effect of the crosslinking agent on the biorepulsive and mechanical properties of polyglycerol membranes

Polyglycerol (PG) based surfaces materials and surfaces are well-established bio-compatible materials. Crosslinking of the dendrimeric molecules via their OH groups improves their mechanical stability up to the point that free-standing materials can be attained. Here, we investigate the effect of different crosslinkers on PG films regarding their biorepulsivity and mechanical properties. For this purpose, PG films with different thicknesses (15, 50 and 100 nm) were prepared by polymerizing glycidol in a ring-opening polymerization onto hydroxyl-terminated Si substrates. These films were then crosslinked using ethylene glycol diglycidyl ether (EGDGE), divinyl sulfone (DVS), glutaraldehyde (GA), 1,11-di(mesyloxy)−3,6,9-trioxaundecane (TEG-Ms2) or 1,11-dibromo-3,6,9-trioxaundecane (TEG-Br2), respectively. While DVS, TEG-Ms2, and TEG-Br2 resulted in slightly thinned films, presumably due to loss of unbound material, increase of film thickness was observed with GA and, in particular, EDGDE, what can be explained by the different crosslinking mechanisms. The biorepulsive properties of the crosslinked PG films were characterized by water contact angle (WCA) goniometry and various adsorption assays involving proteins (serum albumine, fibrinogen, γ-globulin) and bacteria (E. coli), showing that some crosslinkers (EGDGE, DVS) improved the biorepulsive properties, while others deteriorated them (TEG-Ms2, TEG-Br2, GA). As the crosslinking stabilized the films, it was possible to use a lift-off procedure to obtain free-standing membranes if the thickness of the films was 50 nm or larger. Their mechanical properties were examined with a bulge test showing high elasticities, with the Young’s moduli increasing in the order GA ≈ EDGDE < TEG-Br2 ≈ TEG-Ms2 < DVS.

Self-healing hybrid hydrogels with sustained bioactive components release for guided bone regeneration

Guided bone regeneration (GBR) is widely used in treating oral bone defects to exclude the influence of non-osteogenic tissue on the bone healing process. The traditional method of GBR with a titanium mesh to treat large-area bone defects is limited by the deficiency of increased trauma and costs to patients. Herein, a bi-layered scaffold for GBR composed of a fiber barrier layer and a self-healing hydrogel repair layer is successfully fabricated. The barrier layer is a fibrous membrane material with specific porosity constructed by electrospinning, while the functional layer is a self-healing hydrogel material formed by multiple dynamic covalent bonds. The system can provide an osteogenic microenvironment by preventing the infiltration of connective tissue to bone defects, maintain the stability of the osteogenic space through the self-healing property, and regulate the release of bioactive substances in the dynamic physical condition, which is beneficial to osteoblast proliferation, differentiation, and bone regeneration. This study focused on exploring the effects of different crosslinkers and bonding methods on the comprehensive properties of hydrogels. and proved that the hybrid scaffold system has good biocompatibility, cell barrier function and can enhance bone regeneration activity. Thereby it could be a promising clinical strategy for bone regeneration.

Effect of Crosslinker Types on Temporary Plugging Performance of Degradable Preformed Particle Gels for Unconventional Petroleum Reservoir Development

Temporary plugging agents (TPAs) have been widely used in unconventional petroleum reservoirs to increase the stimulated reservoir volume and generate an easier flow of oil and gas into the production well. The properties of particle-gel-based TPAs include a straightforward injection procedure, excellent deformation, strong plugging strength, and total self-degradation. This study prepared degradable preformed particle gel (DPPG) samples polymerized by two types of crosslinkers (i.e., alcohol ester and alkenoic acid ester) for low-temperature (less than 40 °C) reservoirs. The effects of different crosslinkers in the DPPG compositions on the temporary plugging performance were investigated. Infrared spectrum analysis, differential calorimetry scanning evaluation, static particle gel swelling and degradation performance assessment experiments, and dynamic temporary plugging performance tests were all employed. The results showed that the swelling ratio of DPPGs prepared by the crosslinker containing alcohol ester was larger than that of alkenoate acid ester, but the degradation rate was slower. Among them, when the amount of crosslinker was 0.01 g, the swelling ratio of DPPG prepared using the alcohol ester crosslinker was as high as 40 times, and the complete degradation time could be regulated between 80 and 360 h. When the type of crosslinker was the same, the influence of its molecular weight also significantly affected the performance of the particle gel. The plugging strength of DPPG prepared by different crosslinkers in cores was as high as 20 MPa. The DPPG prepared from the alcohol ester crosslinker caused less damage to the core after being self-degraded and was used as an ideal crosslinker. Infrared spectroscopy and differential scanning calorimetry analysis at the molecular level verified that different types of crosslinkers had apparent effects on the chemical structure stability of the DPPG. In this paper, the influence of the type of crosslinker on the performance of the DPPG was studied, which provides a new idea and theoretical basis for developing a particle gel-based TPA system with programmed self-degradation time at low temperatures.

Effect of oxidized sucrose, citric acid crosslinking and dual modification on some physicochemical properties of cassava starch for potential application in packaging films

Background: Crosslinking is one method of starch modification that has been applied to improve the properties of starch and starch-based films. The effects of different crosslinkers on some properties of starch give an insight into the impact the crosslinking modification will have on the final behaviour of starch films. The aim of this study was to analyse the effects of oxidized sucrose and citric acid crosslinking on cassava starch intended for packaging film applications. Methods: Cassava starch was crosslinked with oxidized sucrose and citric acid individually and also in combination (dual modification). The properties studied were amylose content, degree of substitution (DS), degree of crosslinking (DC), solubility, swelling power and paste clarity while FTIR, SEM, XRD and thermal analysis were also carried out. Results: The optimal concentrations of oxidized sucrose and citric acid in this study were 1% and 5% resulting in a maximum amylose content of 20.78 and 19.4 respectively while an intermediate DS (0.182- 0.401) was recorded for all crosslinked starches. The swelling power and solubility of oxidized sucrose crosslinked starch (OS-starch) was lower than that of citric acid crosslinked starch (CA-starch) in all the temperatures observed. The SEM, XRD as well as FTIR analysis highlighted changes in the crystalline structure of starch granules after the crosslinking. Thermo-gravimetric analysis indicated that the thermal stability of all starches was significantly improved by crosslinking, as residual weights of 18.74%, 19.59% and 19.68% were observed for CA-starch, OS-starch, and dual modified starch (OS-CA starch) respectively. Conclusion: Overall, the study suggests that although both crosslinkers significantly improved the physicochemical properties of cassava starch studied, oxidized sucrose had higher effect on most these properties, hence can be suggested to be better suitable when modifying starch for packaging film applications.

Sustainable Cross-Linkers for the Synthesis of Cellulose-Based Aerogels: Research and Application

Cellulose aerogels with polyester resin as cross-linkers have attracted much attention. This study describes the route to produce a fully bio-based aerogel with high added value from waste paper and starch, cellulose acetate and starch–cellulose acetate mixture as cross-linkers for oil adsorption, instead of the environmentally harmful polyester resin. The manufacturing process is simple, sustainable and cost-efficient, without releasing harmful by-products into the environment. The effects of different cross-linkers on the oil adsorption, dynamic oil retention, reusability and morphology of the aerogels were studied in detail. Experimental results show that these environmentally friendly recycled aerogels have a very low density, i.e., —0.0110–0.0209 g cm−3, and highly porous structures, with a porosity of 96.74–99.18%. The synthesized hydrophobic aerogels showed contact angles of ∼124–129°. The compression moduli are lower than that of an aerogel with polyester as a cross-linker, but the compression modulus of the mixture of starch and cellulose acetate especially shows a higher value than expected. The sorption capacity of the aerogels with bio-based cross-linkers was significantly increased compared to the aerogels with polyester; it is now up to 56 times their own weight. The aerogels also have good oil-retention properties.

Developing a liquid and curable two-component precursor system for fabrication of SiC(N)-based composites

Precursor impregnation and pyrolysis (PIP) is an important process to fabricate fiber-reinforced SiC matrix composites, and a low viscous, curable, long-storable, and affordable liquid precursor is urgently needed. To meet the above requirements, a liquid two-component precursor system is proposed, which contains (1) the liquid by-product of polycarbosilane (b-PCS), and (2) organosilicon compound with double carbon bond. The b-PCS with the M‾w value of 635 is mainly composed of the oligomers of carbosilane with abundant amount of Si–H active groups. Four candidates of organosilicon compounds including tetramethyldivinyldisilazane (TMDS), methyltriallysilane (MTAS), Tetraallylsilane(TAS), and 1,3,5-Trivinyl-1,3,5-trimethylcyclotrisilazane (TVSN) were used, called crosslinkers. The effect of different crosslinkers on curing and pyrolysis process was investigated via TG-DSC, FTIR and TG-FTIR-MS, et al. Based on the results of the total ceramic yield, TVSN is the optimized crosslinker of four candidate organosilicon compounds. The ceramic product of corresponding two-component precursor was also characterized via element analysis, compositional element Si, C, N, and O account for 54.77 wt%, 36.23 wt%, 6.83 wt%, 2.07 wt%, respectively. Moreover, the two-component precursor has excellent storage stability at room temperature.

Physical and mechanical properties of alginate-based hydrogel film as carrier for release of acetylthiocholine

The effects of different cross-linkers on mechanical and physical properties of alginate hydrogel films were determined to use prepared films as potential carrier structure for rapid detection system. Xylitol and d-mannitol cross-linked hydrogel films improved mechanical properties and generated more rigid, tough and stretchable film than uncross-linked film. Results exhibited increased tensile strength by 2.3 folds (58.3±5.8 MPa) and 1.8 folds (47.4±4.9MPa) when compared to uncross-linked film (25.8±7.3 MPa) respectively. Young’s modulus of d-mannitol cross-linked film was slightly greater (16.8±2.1 MPa) than that of xylitol (15.7±2.7 MPa) whereas the elongation at break (E%) value of xylitol cross-linking (5.46±1.2%) was greater than d-mannitol (2.72±0.8%) cross-linking. Altered mechanical properties were investigated in terms of different amount of % cumulative release of AchI and DTNB that were immobilized in film matrix. Results showed different release amount depending on types of cross-linkers as following: xylitolcrosslinked (71.5%) > d-mannitol (64.9%) > uncross-linked (58.3%) at 10 min of release period. The exponent value n which determined based on power-law expression was ranged between 0.56 and 0.98, and indicates the release was mediated by anomalous Non-Fickian diffusion.

Synthesis and performance of a novel nanofiltration membrane with a crosslinked sulfonated polysulfone separation layer

The composite nanofiltration membrane was prepared by coating the covalent crosslinked sulfonated polysulfone on porous substrate. Polyethylene glycol (PEG), dopamine (DA) and m-phenylenediamine (MPD) were used as crosslinkers, respectively. The polyethersulfone/sulfonated polysulfone substrate was prepared by phase inversion. The membrane surface chemistry, hydrophilicity, morphology, PWF and rejections of PEG, methyl red and Na2SO4 were characterized. The effects of different crosslinkers and their concentrations on membrane characteristics were investigated. The effect of the sulfonated polysulfone concentration on the membrane characteristic was also investigated. The PEG crosslinked membrane showed the lowest contact angle of 9.0°, the highest PEG-600 rejection of 99.8%, the highest methyl red rejection of 99.8%, and the rejection of Na2SO4 was 93.4% and the PWF was 3.1 L m−2 h−1. The DA crosslinked membrane had the highest PWF of 51.5 L m−2 h−1, and the rejections of PEG-600, methyl red and Na2SO4 were 46.0, 44.0, and 34.0%, respectively. The MPD crosslinked membrane had the lowest PWF and rejections.

Porous ovalbumin scaffolds with tunable properties: a resource-efficient biodegradable material for tissue engineering applications.

Natural materials are promising alternatives to synthetic materials used in tissue engineering applications as they have superior biocompatibility and promote better cell attachment and proliferation. Ovalbumin, a natural polymer found in avian egg white, is an example of a nature-derived material. Despite the availability and reported biocompatibility of ovalbumin, limited research has been carried out to investigate the efficacy of ovalbumin-based scaffolds for adipose tissue engineering applications. Hence, the current study was carried out to investigate the effect of different crosslinkers on ovalbumin scaffold properties as first step towards the development of ovalbumin-based scaffolds for adipose tissue engineering applications. In this study, highly porous three-dimensional scaffolds were fabricated by using three different crosslinkers: glutaraldehyde, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and 1,4-butanediol diglycidyl ether. Results showed that the overall scaffold properties such as morphology, pore size and mechanical properties could be modulated based on the type and concentration of crosslinkers used during the fabrication process. Subsequently, the efficacy of the different scaffolds for supporting cell proliferation was investigated. In vitro degradation was also carried on for the best scaffold based on the mechanical and cellular results. Overall, this study is a demonstration of the viability of ovalbumin-based scaffolds as cell carriers for soft tissue engineering applications.

Studies on Effects of Different Cross-Linkers on the Properties of Starch-Based Wood Composites

A green route is demonstrated to prepare biobased composites from renewable resources like starch and soft wood with engineering aspects. In this process, three different cross-linkers such as glutaraldehyde (GA), dimethyloldihydroxyethyleneurea (DMDHEU), and N-methylol acrylamide (NMA) have been used to cross-link methyl methacrylate-grafted starch with wood flour. Water is used as a solvent and glycerol as a plasticizer in the preparation of wood starch composites. Effects of these cross-linkers on different properties of the composites have been investigated through a limiting oxygen index test and mechanical, dynamic mechanical, and thermogravimetric analysis. DMDHEU cross-linked composites show the least water uptake capacity compared to NMA- and GA-based cross-linked composites due to their better cross-linked structure as DMDHEU contains a higher number of functional groups. The interaction among polymer, cross-linker, and wood has been found to be the maximum in DMDHEU cross-linked composites as revealed by FTIR and SEM studies. DMDHEU cross-linked composites also exhibit higher mechanical and thermal properties.

Breathability studies of electron beam curable polyurethane pressure sensitive adhesive for bio-medical application

Polyurethane (PU) based pressure sensitive adhesive (PSA) commonly used in surgical dressing has been made by electron beam (e-beam) irradiation. In contact with biological substrate like skin, PSAs generally lose their adhesive strength due to very low moisture vapor transmission rate (MVTR). In the present study, effects of varying e-beam dose and different crosslinkers on the MVTR of the PU-PSA have been investigated. A comparative study of effects of different crosslinkers showed that PU-PSA with IPDI has the least while that with TAC has the highest gel content and crystallinity and a reverse trend was observed for the MVTR.

Shrinkage studies in electron beam curable polyurethane pressure-sensitive adhesive

Polyurethane (PU)-based pressure-sensitive adhesive (PSA) has been manufactured by electron beam (e-beam) irradiation using urethane-acrylate. The effect of variation of e-beam dose and crosslinkers viz. triallyl cyanurate (TAC), triallyl isocyanurate, polymeric methylene diphenyl diisocyanate, carbodiimide-modified methylene diphenyl di-isocyanate, methylene diphenyl di-isocyanate, and isophorone di-isocyanate (IPDI) has been studied concerning the shrinkage, adhesion properties, and gel content of the PU-PSA. It was found that with increasing e-beam dose the shrinkage is increased up to 25 kGy, but remained constant thereafter with further increasing the dose up to 60 kGy. Similarly, with increasing concentration of crosslinkers from 2 to 6%, shrinkage is increased but beyond that there is no appreciable change. A comparative study of the effect of different crosslinkers on shrinkage, adhesion properties, and gel content of PU-PSA was carried out, and it was found that TAC leads to the maximum, while IPDI to the lowest shrinkage. However, the opposite was observed for the adhesion properties, i.e. the use of IPDI ensures the maximum and of TAC, the minimum adhesive performance characteristics.

The effect of procyanidine crosslinking on the properties of the electrospun gelatin membranes

In this study, the effect of different crosslinkers including glutaraldehyde (GTA), genipin (GIP) and procyanidine (PA) on the properties of the electrospun gelatin membranes was compared. The water-resistant ability of the membranes could be significantly improved after being crosslinked with PA at T > 40 °C. In contrast with GTA and GIP, the PA-crosslinking process did not apparently affect the fibrous structure, and induced the lowest shrinkage of the membranes. At the concentration of 5% of PA, the ultimate tensile strength and elongation of the hydrated membrane were 0.87 MPa and 148%, respectively, which were higher than those of the GIP-crosslinked counterparts. In addition, the PA-crosslinked membranes displayed the highest resistance to pepsin degradation, and fibroblast cells could migrate deeper into the interior of the membranes due to the good preservation of the fibrous structure during the cell culture process.

Alginates as binding matrix for bio‐molluscicides against harmful snails Lymnaea acuminata

AbstractVarious properties of alginates, such as its biodegradability, nontoxicity, biocompatibility, and ability to form gel with a variety of crosslinking agents in mild and aqueous conditions, make it a very useful binding matrix. Use of alginates as binding matrix for bio‐molluscicides (crude Annona squamosa powder and acetogenin extracted from the seed powder of A. squamosa) is explored in this article. Effect of different crosslinkers as well as different loaded concentrations of biomolluscicides on the release were studied The release of the biomolluscicides extended over 25 and 20 days, respectively. The release was affected by the type of crosslinker and the amount of loaded concentration of the molluscicides. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Changes in mechanical properties and cellularity during long‐term culture of collagen fiber ACL reconstruction scaffolds

Resorbable scaffolds for anterior cruciate ligament (ACL) reconstruction should provide temporary mechanical function then gradually breakdown while promoting matrix synthesis by local cells. Crosslinking influences collagen's mechanical properties, degradation rate, and interactions with cells. Our objective was to compare the effects of different crosslinkers on cellularity and mechanical properties during long-term (8 week) culture of collagen fiber scaffolds. Fibers were fabricated from an acid-insoluble dispersion of bovine dermal collagen and crosslinked with either ultraviolet irradiation (UV; a physical crosslinker) or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC; a chemical crosslinker). Scaffolds consisted of 50 fibers bundled in parallel. Initial attachment of fibroblasts was similar on both scaffolds; however, from 1 to 8 weeks in culture, UV-crosslinked scaffolds had significantly more cells attached than EDC-crosslinked scaffolds. The initial breaking load (3.50 N) and stiffness (2.23 N/mm) of EDC-crosslinked scaffolds were significantly greater than those of UV-crosslinked scaffolds (2.32 N; 1.21 N/mm) and were unaffected by long-term fibroblast culture. In contrast, the load-bearing capacity of fibroblast-seeded UV-crosslinked scaffolds decreased 60% to 0.91 N after 8 weeks in culture. EDC-crosslinked scaffolds maintained strength and moderate cellularity; UV-crosslinked scaffolds, in contrast, were highly cellular, but had poor mechanical properties that decreased during culture. These in vitro results suggest that collagen fiber scaffolds crosslinked with EDC may be more suitable for ACL reconstruction than those crosslinked with UV.