Polycaprolactone (PCL) is a semicrystalline thermoplastic polymer well-known as a nontoxic and biodegradable material. Due to this nature, PCL has been studied for drug delivery and a bioscaffold in tissue engineering. However, it has incomplete properties as the structural materials such as relatively low mechanical properties, low surface energy, and long degradation rates. Thus, this study aims to complement the previous shortcomings and present the possibility of a more advanced biomaterial by forming nanocomposites with cellulose nanocrystal (CNC), one of the abundant natural polymers with high specific modulus and strength, environmentally-friendliness, and nontoxic. Bulk materials with various concentrations of CNC in PCL matrix were fabricated, and a three-point bending test was conducted. The measured bending modulus was compared with the estimated values based on the rule of mixtures of the nanocomposite and surface morphology was investigated by scanning electron microscopy.
Cellulose nanofibers (CNFs) have attracted attention in a diverse area of applications due to their amazing mechanical properties and lightweight. Recent advances in enhancing the mechanical performance of nanocellulose filaments and films have reported efforts to align the individual cellulose nanofibers using different methods. Among them, the most recent being the use of electrical fields experimentally. It is important to investigate at the molecular level if the application of low electric fields on CNF can induce alignment and what effects these electric fields have on the molecular structure of the CNF. This study reports a molecular dynamics (MD) study of CNF model in a varying electric field (EF) strengths and direction. The MD simulations were conducted in GROningen Machine for Chemical Simulations (GROMACS) and the All-Atom Optimized Potential for Liquid Simulations (OPLS-AA) force field was used. Induced electric field alignment was investigated in terms of how quickly the alignment begins, how long it takes for complete alignment, and the ability to maintain any achieved alignment at different electric fields. To understand the electric field-induced structural changes, the hydrogen bonding network, hydrogen bond length, radius of gyration, and deviation from the original model are critically analyzed. The results show that CNF can be successfully aligned in low electric fields without compromising its molecular structure.
Cellulose, a natural fiber, has been employed vastly for structural components due to its high mechanical strength and young’s modulus. The hydrophilic hydroxyl groups on the surface of cellulose nanofiber enables formation of cellulose-based nanocomposites with high mechanical properties which has been widely studied. The interfacial bonding of the composites between cellulose and other polymers could be improved further by surface modification of cellulose. Aiming to improve the mechanical properties of cellulose nanofiber and its composites as well as functional properties, a bio-inspired approach to coating polydopamine onto cellulose nanofiber was developed. Due to strong adhesion ability and self-polymerization of dopamine in tris buffer, polydopamine could be easily coated on cellulose nanofiber under mild conditions. Prefabricated cellulose nanofiber film and filament were modified by coating with polydopamine. FTIR, XPS, SEM confirmed a homogeneous polydopamine coating on cellulose nanofiber film and filament. The mechanical strength and stiffness of the cellulose-polydopamine fiber and the respective composite materials were investigated. The photostability, antibacterial, and electrical properties of the polydopamine-cellulose nanofiber were also studied.
Being a naturally occurring biopolymer, cellulose is popular and deeply explored for its amazing mechanical properties. Cellulose nanofibers are modelled and molecular dynamics simulations conducted using GROMACS and All-Optimized Potential for Liquid Simulations (OPLS-AA) force field is used for parameterization. The mechanical properties and structural stability of the cellulose nanofibers are investigated via the simulations. We explore the hydrogen bonding disparities on the CNF structure as it is subjected to different pull forces. The results show that the hydrogen bonds decrease every time a pull force is increased, with the decrement more significant when large pull forces are applied than low pull forces.
Surface-functionalizations are of essential importance for diverse areas from biomedicine to biosensing, nanocomposites, water treatment, and energy harvesting devices. One facile and rapid way to functionalize any materials surface is by mussel inspired polydopamine (PDA) coating. It has been realized that dopamine (DA), the precursor, can be coated virtually on any substrates in presence of a buffer of pH ~ 8.5. Over the past 20 years, an overwhelming interest has been noticed around cellulose based materials specially nanofibers (CNFs) shown due to its many unique characteristics including high stiffness and modulus, great transparency well biodegradability, biocompatibility and low production cost. Despite of the facts, pristine cellulose often suffers from certain characteristic limitations in biomaterial applications due to the lack of appropriate surface functionalities. This research therefore aims to develop cellulose based composite materials suitable for biomedical applications, precisely electrode material for biosensors. The electrodes were made of controlled amount of polydopamine treated cellulose nanofiber composite. When investigated the mechanical properties of the composites, significant improvement was observed. Moreover, the composites exhibited good sensing behaviors under electrochemical investigations, leading them to be a promising material for biosensing applications.
Atomic force microscopy (AFM) is known for measuring the mechanical properties of nanomaterials. It has been used for measuring the mechanical properties of few kinds of fibers, such as carbon nanotubes, gold nanofibers, graphene. In this study, the effect of various sources on the elastic modulus of cellulose nanofibers (CNFs) was investigated by using AFM three-points bending test. The CNFs were extracted from hardwood, softwood, bamboo and cotton by using aqueous counter collision (ACC) system and the morphology of CNFs were studied by AFM. CNFs were successfully transferred to the AFM calibration chip and the three-points bending test was performed. CNFs were considered to be circular shape by taking into account the AFM tip radius and the Young’s modulus was calculated. The calculation results indicate that the range of Young’s modulus is between 102 and 131 GPa varying upon the cellulose resources.
Cellulose is the most naturally occurring biomolecular polymers ensemble into cellulose nanofibers that has both amorphous and crystalline domains in proportions dependent on the source. Cellulose nanofibrils have raised significant interest as excellent structural materials with exceptional mechanical properties. It is important to understand the structure of CNF and its synergy. This study entails molecular dynamics simulations of the cellulose nanofibrils to give insightful understanding of its atomic details in response to temperature. GROningen Machine for Chemical Simulations (GROMACS) is used as the simulations software and All-Atom Optimized Potential for Liquid Simulations (OPLS-AA) force field is chosen for the simulation. To understand the thermally induced structural changes, lattice parameters, crystal density, hydrogen bonding network and other parameters are critically analyzed. The total number of hydrogen bonds is also observed.
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