Preparation and Characterization of pH Sensitive Chitosan/3-Glycidyloxypropyl Trimethoxysilane (GPTMS) Hydrogels by Sol-Gel Method

pH responsive chitosan and 3-Glycidyloxypropyl trimethoxysilane (GPTMS) hydrogels were synthesized by the sol-gel crosslinking reaction. GPTMS was introduced to influence several behaviors of the chitosan hydrogels, such as the swelling ratio, mechanical properties, swelling thermodynamics, kinetics, and expansion mechanism. The functional groups of Chitosan/GPTMS hybrid hydrogels were verified by FT-IR spectrometer. Differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA) were used to analyzed the thermal behavior of water molecules, the expansion of thermodynamics, and the content of water molecules in the hydrogel. The results show that hydrogel consists of 50 wt.% GPTMS (CG50) and has good mechanical properties and sensitivity to pH response characteristics in the acidic/alkaline buffer solution. The increase of GPTMS content leads to the increase of hydrophobic groups in the hydrogel and causes the decrease of the overall water content and the freezing bond water content. When the hydrogels were immersed in acid solution, the interaction force parameter was smaller than that of DI-water and alkaline. It means that the interaction forces between hydrogel and water molecules are relatively strong. The swelling kinetics of hybrid hydrogels were investigated to inspect the swelling mechanism. The result is consistent with the Fisk’s diffusion mechanism, meaning that the rate of water penetration is adjustable. The biodegradable hydrogel (CG50) in this study has good environmental sensitivity and mechanical properties. It is suitable to be applied in the fields of drug release or biomedical technology.

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Oxazoline-based crosslinking reaction for coatings

Journal of Coatings Technology and Research ◽

10.1007/s11998-021-00479-9 ◽

2021 ◽

Author(s):

Philipp Knospe ◽

Patrick Böhm ◽

Jochen Gutmann ◽

Michael Dornbusch

Keyword(s):

Mechanical Properties ◽

Loss Modulus ◽

New Technology ◽

Sol Gel ◽

Polymer Network ◽

Time Dependent ◽

Crosslinking Reaction ◽

Coating Materials ◽

Rheological Measurements ◽

Excellent Adhesion

AbstractNowadays, coating materials must meet high demands in terms of mechanical, chemical and optical properties in all areas of application. Amongst others, amines and isocyanates are used as crosslinking components for curing reactions, meeting the highly demanding properties of the coatings industry. In this work, a new crosslinking reaction for coatings based on oxazoline chemistry is investigated with the objective to overcome disadvantages of established systems and fulfill the need for sustainable coating compounds. The oxazoline-group containing resin, synthesized from commercially available substances, undergoes cationic self-crosslinking polymerization to build up a network based on urethane and amide moieties. NMR-, IR- and ES-mass spectroscopy are suitable techniques to characterize the synthesized oxazoline monomers, which are linked to polyisocyanates and polymerized afterwards via self-polymerization. The progress of crosslinking is followed by changes in IR spectra and by rheological measurements to calculate time dependent values for storage and loss modulus. The glass transition temperature of the resulting coating is determined, too. Furthermore, sol–gel-analysis is performed to determine the degree of crosslinking. After application on steel and aluminium panels, application tests are performed. In addition to excellent adhesion to the substrate, the polymer network shows promising mechanical properties and with that it could represent a new technology for the coatings industry.

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Novel Chitosan-Silica Hybrid Hydrogels for Cell Encapsulation and Drug Delivery

International Journal of Molecular Sciences ◽

10.3390/ijms222212267 ◽

2021 ◽

Vol 22 (22) ◽

pp. 12267

Author(s):

Soher N. Jayash ◽

Paul R. Cooper ◽

Richard M. Shelton ◽

Sarah A. Kuehne ◽

Gowsihan Poologasundarampillai

Keyword(s):

Mechanical Properties ◽

Sol Gel ◽

Cell Encapsulation ◽

Biological Properties ◽

Aqueous Environment ◽

Absorption Bands ◽

Hybrid Hydrogels ◽

Oscillatory Rheometry ◽

3D Cell Cultures

Hydrogels constructed from naturally derived polymers provide an aqueous environment that encourages cell growth, however, mechanical properties are poor and degradation can be difficult to predict. Whilst, synthetic hydrogels exhibit some improved mechanical properties, these materials lack biochemical cues for cells growing and have limited biodegradation. To produce hydrogels that support 3D cell cultures to form tissue mimics, materials must exhibit appropriate biological and mechanical properties. In this study, novel organic-inorganic hybrid hydrogels based on chitosan and silica were prepared using the sol-gel technique. The chemical, physical and biological properties of the hydrogels were assessed. Statistical analysis was performed using One-Way ANOVAs and independent-sample t-tests. Fourier transform infrared spectroscopy showed characteristic absorption bands including amide II, Si-O and Si-O-Si confirming formation of hybrid networks. Oscillatory rheometry was used to characterise the sol to gel transition and viscoelastic behaviour of hydrogels. Furthermore, in vitro degradation revealed both chitosan and silica were released over 21 days. The hydrogels exhibited high loading efficiency as total protein loading was released in a week. There were significant differences between TC2G and C2G at all-time points (p < 0.05). The viability of osteoblasts seeded on, and encapsulated within, the hydrogels was >70% over 168 h culture and antimicrobial activity was demonstrated against Pseudomonas aeruginosa and Enterococcus faecalis. The hydrogels developed here offer alternatives for biopolymer hydrogels for biomedical use, including for application in drug/cell delivery and for bone tissue engineering.

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Using Graphene Sulfonate Nanosheets to Improve the Properties of Siliceous Sacrificial Materials: An Experimental and Molecular Dynamics Study

Materials ◽

10.3390/ma13214824 ◽

2020 ◽

Vol 13 (21) ◽

pp. 4824 ◽

Cited By ~ 1

Author(s):

Hongyan Chu ◽

Zifei Wang ◽

Yu Zhang ◽

Fengjuan Wang ◽

Siyi Ju ◽

...

Keyword(s):

Mechanical Properties ◽

Molecular Dynamics ◽

High Performance ◽

Pore Diameter ◽

Water Molecules ◽

Scanning Calorimetry ◽

Optimal Amount ◽

Cement Based Materials ◽

Decomposition Enthalpy ◽

Sacrificial Materials

The fabrication of high-performance cement-based materials has benefited greatly from the extensive use of graphene and its derivatives. This paper studies the effects of graphene sulfonate nanosheets (GSNSs) on sacrificial cement paste and mortar (the tested materials) and other siliceous sacrificial materials, especially their ablation behaviors and mechanical properties. Decomposition temperatures and differential scanning calorimetry were used to examine how different contents of GSNSs determines the corresponding decomposition enthalpy of the tested materials and their ablation behaviors. Molecular dynamics was also used to clarify the mechanism how the GSNSs work in the CSH (calcium silicate hydrated)/GSNSs composite to increase the resistance to high temperature. The experimental results show that: (1) the contents of GSNSs at 0.03 wt.%, 0.1 wt.%, and 0.3 wt.% brought an increase of 10.97%, 22.21%, and 17.56%, respectively, in the flexural strength of siliceous sacrificial mortar, and an increase of 1.92%, 9.16%, and 6.70% in its compressive strength; (2) the porosity of siliceous sacrificial mortar was decreased by 5.04%, 9.91%, and 7.13%, respectively, and the threshold pore diameter of siliceous sacrificial mortar was decreased by 13.06%, 35.39%, and 24.02%, when the contents of GSNSs were 0.03 wt.%, 0.1 wt.%, and 0.3 wt.%, respectively; (3) a decline of 11.16%, 28.50%, and 61.01% was found in the ablation velocity of siliceous sacrificial mortar, when the contents of GSNSs were 0.03 wt.%, 0.1 wt.%, and 0.3 wt.%, respectively; (4) when considering the ablation velocities and mechanical properties of siliceous sacrificial materials, 0.1 wt.% GSNSs was considered to be the optimal amount; (5) the GSNSs contribute to the reinforced effect of GSNSs on CSH gel through the grab of dissociated calcium and water molecules, and the chemical reaction with silicate tetrahedron to produce S–O–Si bonds. These results are expected to promoting the development of new kinds of siliceous sacrificial materials that contain GSNSs.

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Biomimetic Mineralization of Tannic Acid-Supplemented HEMA/SBMA Nanocomposite Hydrogels

Polymers ◽

10.3390/polym13111697 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1697

Author(s):

Tai-Yu Chen ◽

Shih-Fu Ou ◽

Hsiu-Wen Chien

Keyword(s):

Mechanical Properties ◽

Water Content ◽

Tannic Acid ◽

Chemical Structure ◽

Fold Increase ◽

Biomimetic Mineralization ◽

X Ray ◽

Nanocomposite Hydrogels ◽

Hybrid Hydrogels ◽

Structure Water

This study developed a tannic acid (TA)-supplemented 2-hydroxyethyl methacrylate-co-sulfobetaine methacrylate (HEMA-co-SBMA) nanocomposite hydrogel with mineralization and antibacterial functions. Initially, hybrid hydrogels were synthesized by incorporating SBMA into the HEMA network and the influence of SBMA on the chemical structure, water content, mechanical properties, and antibacterial characteristics of the hybrid HEMA/SBMA hydrogels was examined. Then, nanoclay (Laponite XLG) was introduced into the hybrid HEMA/SBMA hydrogels and the effects evaluated of the nanoclay on the chemical structure, water content, and mechanical properties of these supplemented hydrogels. The 50/50 hybrid HEMA/SBMA hydrogel with 30 mg/mL nanoclay showed outstanding mechanical properties (3 MPa) and water content (60%) compared to pure polyHEMA hydrogels. TA then went on to be incorporated into these hybrid nanocomposite hydrogels and its effects investigated on biomimetic mineralization. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) showed that bone-like spheroidal precipitates with a Ca/P ratio of 1.67% were observed after 28 days within these mineralized hydrogels. These mineralized hydrogels demonstrated an almost 1.5-fold increase in compressive moduli compared to the hydrogels without mineralization. These multifunctional hydrogels display good mechanical and biomimetic properties and may have applications in bone regeneration therapies.

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Preparation, Characterization, and Enhanced Thermal and Mechanical Properties of Epoxy-Titania Composites

The Scientific World JOURNAL ◽

10.1155/2014/515739 ◽

2014 ◽

Vol 2014 ◽

pp. 1-7 ◽

Cited By ~ 19

Author(s):

Zakya Rubab ◽

Adeel Afzal ◽

Humaira M. Siddiqi ◽

Shaukat Saeed

Keyword(s):

Mechanical Properties ◽

Elevated Temperatures ◽

Sol Gel ◽

High Stress ◽

Thermal And Mechanical Properties ◽

Mechanical Mixing ◽

Scanning Calorimetry ◽

X Ray ◽

Thermal Oxidative Stability ◽

Epoxy Polymers

This paper presents the synthesis and thermal and mechanical properties of epoxy-titania composites. First, submicron titania particles are prepared via surfactant-free sol-gel method using TiCl4as precursor. These particles are subsequently used as inorganic fillers (or reinforcement) for thermally cured epoxy polymers. Epoxy-titania composites are prepared via mechanical mixing of titania particles with liquid epoxy resin and subsequently curing the mixture with an aliphatic diamine. The amount of titania particles integrated into epoxy matrix is varied between 2.5 and 10.0 wt.% to investigate the effect of sub-micron titania particles on thermal and mechanical properties of epoxy-titania composites. These composites are characterized by X-ray photoelectron (XPS) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric (TG), and mechanical analyses. It is found that sub-micron titania particles significantly enhance the glass transition temperature (>6.7%), thermal oxidative stability (>12.0%), tensile strength (>21.8%), and Young’s modulus (>16.8%) of epoxy polymers. Epoxy-titania composites with 5.0 wt.% sub-micron titania particles perform best at elevated temperatures as well as under high stress.

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Influence of sol–gel derived silica-based interfacial coatings on the mechanical properties of carbon–carbon composites

Carbon ◽

10.1016/s0008-6223(02)00387-1 ◽

2003 ◽

Author(s):

S Dhakate

Keyword(s):

Mechanical Properties ◽

Sol Gel ◽

Carbon Composites

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Hydrogels as Antibacterial Biomaterials

Current Pharmaceutical Design ◽

10.2174/1381612824666180213122953 ◽

2018 ◽

Vol 24 (8) ◽

pp. 843-854 ◽

Cited By ~ 6

Author(s):

Weiguo Xu ◽

Shujun Dong ◽

Yuping Han ◽

Shuqiang Li ◽

Yang Liu

Keyword(s):

Mechanical Properties ◽

Drug Delivery ◽

Tissue Engineering ◽

Water Content ◽

Oxygen Permeability ◽

Structural Diversity ◽

High Water ◽

Clinical Applications ◽

High Water Content ◽

Biomedical Field

Hydrogels, as a class of materials for tissue engineering and drug delivery, have high water content and solid-like mechanical properties. Currently, hydrogels with an antibacterial function are a research hotspot in biomedical field. Many advanced antibacterial hydrogels have been developed, each possessing unique qualities, namely high water swellability, high oxygen permeability, improved biocompatibility, ease of loading and releasing drugs and structural diversity. In this article, an overview is provided on the preparation and applications of various antibacterial hydrogels. Furthermore, the prospects in biomedical researches and clinical applications are predicted.

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