Effect of Chitin Whiskers on the Molecular Dynamics of Carrageenan-Based Nanocomposites

From fundamental insights to rational (bio)polymer nanocomposite design - Connecting the nanometer to meter scale

Nanoparticle addition has the potential to make bioplastic use mainstream, as the resultant nanocomposite shows improved mechanical, barrier, and thermal properties. It is well established that the architecture and dynamics of the nanoparticle-polymer interphasial region, ∼ 1.5-9 nm from the nanoparticle surface, are crucial for nanocomposite characteristics. Yet, how these molecular phenomena translate to the bulk is still largely unknown. A multi-disciplinary and multi-scale vision is required to capture the full picture and improve materials far beyond what is currently possible. In this review, a first step in bridging the apparent gap between fundamental insights toward observed material properties is made. At the molecular scale, the polymer chain density and dynamics at the nanoparticle surface are governed by a complex interplay between enthalpy and entropy. The resultant interphasial properties can only be propagated to the macroscopic scale effectively when the nanoparticles are well-distributed. This makes the dispersion state a key parameter for which thermodynamic and kinetic insights can be used to prevent nanoparticle aggregation. These insights are linked to material properties relevant to packaging. The outlook section elaborates on the remaining challenges and the steps required to further understand and better design nanocomposite systems.

A review on chitosan and alginate-based microcapsules: Mechanism and applications in drug delivery systems

Natural polymers, like chitosan and alginate have potential of appearance, as well as the changes and handling necessary to make it acceptable vehicle for the controlled release of medicines and biomolecules. Microcapsules are characterized as micrometer-sized particulate that can be employed to store chemicals within them. In the present review, we have discussed various advantages, components of microcapsules, release mechanisms, preparation methods, and their applications in drug delivery systems. The preparation methods exhibited strong encapsulation effectiveness and may be used in a wide range of pharmaceutical and biomedical applications. The major advantages of using the microencapsulation technique are, sustained and controlled delivery of drugs, drug targeting, improvement of shelf life, stabilization, immobilization of enzymes and microorganisms. As new biomaterials are developed for the body, they are better suited to the development of pharmaceutical systems than traditional pharmaceuticals because they are more reliable, biocompatible, biodegradable, and nontoxic. Furthermore, the designed microcapsules had been capable of shielding the essential components from hostile environments. More advanced techniques could be developed in the future to facilitate the formulation and applications of microcapsules and working with the pharmaceutical and medical industries.

Nanochitin: Chemistry, Structure, Assembly, and Applications

Chitin, a fascinating biopolymer found in living organisms, fulfills current demands of availability, sustainability, biocompatibility, biodegradability, functionality, and renewability. A feature of chitin is its ability to structure into hierarchical assemblies, spanning the nano- and macroscales, imparting toughness and resistance (chemical, biological, among others) to multicomponent materials as well as adding adaptability, tunability, and versatility. Retaining the inherent structural characteristics of chitin and its colloidal features in dispersed media has been central to its use, considering it as a building block for the construction of emerging materials. Top-down chitin designs have been reported and differentiate from the traditional molecular-level, bottom-up synthesis and assembly for material development. Such topics are the focus of this Review, which also covers the origins and biological characteristics of chitin and their influence on the morphological and physical-chemical properties. We discuss recent achievements in the isolation, deconstruction, and fractionation of chitin nanostructures of varying axial aspects (nanofibrils and nanorods) along with methods for their modification and assembly into functional materials. We highlight the role of nanochitin in its native architecture and as a component of materials subjected to multiscale interactions, leading to highly dynamic and functional structures. We introduce the most recent advances in the applications of nanochitin-derived materials and industrialization efforts, following green manufacturing principles. Finally, we offer a critical perspective about the adoption of nanochitin in the context of advanced, sustainable materials.

Applications of emerging botanical hydrocolloids for edible films: A review

In recent years, many studies have been conducted on the production of edible films from emerging gums, which are mostly made from botanical sources. However, each one interacts differently with the film compounds, producing films with different properties that may improve or hinder their utilization in food packaging. Therefore, the aim of this review was to investigate and compare the physical, mechanical, thermal and structural properties of edible films produced with these emerging gums. The results of this review showed that it is possible to produce edible films with desirable physical, mechanical and thermal properties by optimizing the amounts and type of compounds in film formulations such as plasticizers, nanoparticles, lipid compounds, crosslinkers and combination of gums with other biopolymers. The future trends of this research include the deepening of knowledge to understand the molecular structures of emerging gums and to address the shortcomings of films based on these gums for their industrial-scale application in food packaging.

Engineered Multilayer Microcapsules Based on Polysaccharides Nanomaterials

The preparation of microcapsules composed by natural materials have received great attention, as they represent promising systems for the fabrication of micro-containers for controlled loading and release of active compounds, and for other applications. Using polysaccharides as the main materials is receiving increasing interest, as they constitute the main components of the plant cell wall, which represent an ideal platform to mimic for creating biocompatible systems with specific responsive properties. Several researchers have recently described methods for the preparation of microcapsules with various sizes and properties using cell wall polysaccharide nanomaterials. Researchers have focused mostly in using cellulose nanomaterials as structural components in a bio-mimetic approach, as cellulose constitutes the main structural component of the plant cell wall. In this review, we describe the microcapsules systems presented in the literature, focusing on the works where polysaccharide nanomaterials were used as the main structural components. We present the methods and the principles behind the preparation of these systems, and the interactions involved in stabilizing the structures. We show the specific and stimuli-responsive properties of the reported microcapsules, and we describe how these characteristics can be exploited for specific applications.

Compression Shear Properties of Adhesively Bonded Single-Lap Joints of C/C Composite Materials at High Temperatures

The performance of joint structure is an important aspect of composite material design. In this study, we examined the compression shear bearing capacity of the adhesively bonded single-lap joint structure of high-temperature-resistant composite materials (C/C composite materials). The test pieces were produced in accordance with the appropriate ASTM C1292 standard, which were used for the compression shear test. The failure morphology of the layer was observed by a digital microscopic system and scanning electron microscope. The experimental result shows that the load on the test piece increased nonlinearly until the failure occurred, and most of the adhesive layer exhibited cohesive failures at three temperature points (400, 600, and 800 °C), while the interface failures occurred in a small part of the adhesive layer. A numerical analysis model was established using ABAQUS finite element software. The simulation results were compared with the test results to verify the correctness of the model. On the basis of correctness of the model verified by comparing the simulation results and the test results, the influences of temperature and overlapped length on the joint compression shear performance were studied through the validated simulation method. Numerical results showed that the ultimate load of the joint decreased with increases in temperature and that the distribution trends of the shear stresses in the overlapped length direction were substantially the same for joints of different overlapped lengths.

Effect of Bay Leaves Essential Oil Concentration on the Properties of Biodegradable Carboxymethyl Cellulose-Based Edible Films

Films containing bay leaves essential oils (BEOs) were prepared and evaluated for edible packaging applications. The BEOs were extracted by the Soxhlet method, using ethanol or methanol as organic solvent. Then, films were prepared by “solvent casting” technique using carboxymethyl cellulose (CMC), with different concentrations for the as-obtained BEOs (from 1% to 30% wt.). The resulting films were characterized to evaluate their physical (thickness, moisture content, water solubility and water vapor permeability), optical (transparency and UV-light barrier), mechanical (tensile strength and elongation at break), antioxidant and antimicrobiological properties Attractive films were obtained for food active packaging applications, as they presented a high antioxidant activity (up to 99%) and total phenolic content, and good barrier properties against water vapor (50% improved of CMC) in the case of CMC-film containing 15% wt. ethanolic extract. Related to optical properties, UV-light barrier effect was increased (almost 100% of protection) avoiding typical lipids oxidation in food systems. High water solubility (93%) was also found, ensuring also their biodegradability. Moreover, it was demonstrated that developed films inhibit microorganisms’ growth (Escherichia coli and Candida glabrata), this avoiding an early food oxidation.