Stimuli-responsive polymers, also known as smart polymers, exhibit reversible, significant physical or chemical transformations in response to slight changes in their environment. To further progress the field of smart polymers and their applications, there has been a global drive of multidisciplinary research involving scientists from diverse disciplines.
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Utilization of Multipurpose Smart Conducting Polymers in Food Packaging
Over the past few decades, food packaging markets have captured the attention of researchers due to their direct impact on human health. Both metallic and nonmetallic materials find use in the food and pharmaceutical industries. Among these, materials like tinplate and aluminum are prevalent due to their durability, gas barrier properties, and various practical functionalities. As a result, they are widely employed in packaging markets and are highly effective as food containers.
In recent decades, conventional packaging methods have showcased several issues, leading to a significant gap in the food industry. Particularly concerning is the utilization of plastics in the food markets since these materials are not biodegradable, posing a major concern in today's environmental context.
The latest article published in Industrial & Engineering Chemical Research states that smart conducting polymers doped with nanomaterials are the ideal choice for food packaging specifically due to their stability and ease of preparation. These polymers are also distinguished by their electro-activity, enabling them to be doped with diverse species.
The emerging next-generation packaging boasts multiple functional properties, including antioxidants, antibacterial agents, and toxic gas sensors, ensuring optimal protection for packaged products and extending their shelf-life significantly. Nevertheless, it is crucial, as stated in the article, to conduct toxicity studies on such polymers in the future. Public concern has arisen regarding the toxicity of active smart polymer packaging that relies on nanomaterials and its potential environmental impact on consumers.
Furthermore, an intriguing aspect to explore is the development of a standardized apparatus for testing the newly devised smart polymeric materials as food packaging when they come into contact with food items.
How are Smart Polymers Revolutionizing Cancer Immunotherapy?
Cancer remains one of the primary causes of death worldwide, contributing significantly to the global disease burden. Projections suggest that by 2040, there will be an alarming 29.5 million new cancer cases and a staggering 16.4 million cancer-related deaths.
Over the past 130 years, substantial progress has been made in cancer treatment, with immunotherapy standing out as a revolutionary approach. Immunotherapy has the potential to transform cancer treatment by overcoming the tumor's immune escape mechanism and reinvigorating the immune system to combat cancer cells effectively. However, significant challenges persist, including limited patient response and the immunosuppression of the tumor microenvironment, which are a hurdle in fully harnessing the potential of immunotherapy.
As per the latest article published in Pharmaceuticals, targeted drug delivery aims to transport therapeutic agents precisely to their intended action sites. Smart polymers, owing to their versatility and ability to adapt to various biological properties, offer a safe and effective means to deliver chemotherapeutic agents. The utilization of targeted polymer nanoparticles further enhances the control of drug bio-distribution and bioavailability.
The tumor microenvironment exhibits a distinctly acidic nature in comparison to normal tissue. Dysregulated glycolysis in cancer cells leads to elevated lactate levels and an acidic pH in tumor tissues. Tumor tissue pH typically ranges from 6.5 to 7.2, whereas intracellular fluid pH is normally 5.0 to 6.5. By employing pH-responsive polymer carriers, drug delivery efficiency in vivo can be significantly improved while also reducing adverse drug reactions by leveraging the unique characteristics of the polymer.
In addition, temperature-responsive drug delivery strategies capitalize on the local temperature elevation at the focal site to achieve targeted drug release. Typically, the activation temperature range for drug delivery systems falls between 37 and 42 ºC, as temperatures beyond this range may lead to protein denaturation, causing potential adverse effects.
Shape Memory Polymers – The Most Effective Type of Smart Polymers
Researchers have presented their research recently in Polymers, focusing on the advantages of shape memory polymers (SMPs) as the most efficient smart polymers.
Shape memory polymers (SMPs) are intelligent materials capable of being deformed and locked into a temporary shape, which can then recover their original permanent shape when exposed to an external stimulus. One striking characteristic of SMPs is their ability to retain more than two temporary shapes during the shape memory effect (SME) process, making them excellent candidates for smart systems that require control under various conditions and multiple external stimuli. In the shape memory effect, the SMPs memorize their original permanent shape through net points responsible for maintaining it, while the reversible shape change of SMPs is achieved through switching domains responsible for the temporary shapes.
Utilizing the properties of these particular types of smart polymers, researchers are using them for the development of artificial muscle fibers, as demonstrated by the research published in the International Journal of Engineering.
The mechanical limitations of SMPs restrict their application in structural sectors; however, they can be extensively utilized in areas where the mechanical response of the parts is of lesser concern. This has opened up avenues for the use of SMPs in bio-medical parts.
In recent developments, muscle fibers have been created using a combination of polymers with low transitional temperatures and thermoplastic elastomers blended with high-stiffness polymers like polylactic acid (PLA). Such blends exhibit network points and molecular switching phases formed through covalent bonds, intermolecular interactions, and cross-links.
To produce SMP alloyed films, a two-roller device was employed to melt and mix the polymer components, including TPU (0 to 70%), ABS (0 to 70%), and EVA (0 to 50%), under heat and intense shear forces. The inclusion of EVA in the alloyed systems was found to increase fiber elongation, while the addition of the ABS phase led to higher modulus values. The results revealed strong correlations between the tensile behavior, retraction, and energy release of SMPs upon thermal actuation. These fibers are highly recommended for the fabrication of synthetic muscles.
Progress in Additive Manufacturing of Smart Polymers
Recent advancements in additive manufacturing (AM) techniques have enabled the fabrication of smart polymers and polymeric composites, resulting in personalized, unique, and complex structures capable of adapting to external conditions over time. The flexibility of AM processes in producing intricate and precisely tailored materials with optimized properties has led to numerous industrial applications.
According to the latest article published in Polymer Composites, AM techniques are also referred to as 3D printing (3DP) processes. 3DP goes beyond creating static 3D objects with limited functions and extends to producing multifunctional and shape-variable structures throughout their life cycle, a concept known as 4D printing (4DP).
The use of smart polymers in 3D printed stimuli-responsive structures has shown significant progress, particularly in developing novel materials for various applications. Exploring the performance of reversible micro/macrostructure smart polymers in biomedical applications holds great potential.
While temperature-responsive polymers are extensively studied for additive manufacturing, there is still a lack of evaluation concerning the glass transition temperatures of different materials, which is a crucial aspect in various applications and requires further attention.
In short, smart polymers have a bright future expanding the horizons of materials science. Their applications in modern genetics, textile engineering, synthetic fiber fabrication, and food packaging have sparked a massive research interest in the field of smart polymers.
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References and Further Reading
El Guerraf. et. al. (2022). Multifunctional Smart Conducting Polymers–Silver Nanocomposites-Modified Biocellulose Fibers for Innovative Food Packaging Applications. Industrial & Engineering Chemistry Research. 62(11). 4540-4553. Available at: https://doi.org/10.1021/acs.iecr.2c01327
Yu Z. et. al. (2023). Smart Polymeric Nanoparticles in Cancer Immunotherapy. Pharmaceutics. 15(3). 775. Available at: https://doi.org/10.3390/pharmaceutics15030775
Dayyoub T. et. al. (2022). Shape Memory Polymers as Smart Materials: A Review. Polymers. 14(17):3511. Available at: https://doi.org/10.3390/polym14173511
Karevan M. et. al. (2023). High energy release-high retraction smart polymer fibers used in artificial muscle fabrication. International Journal of Engineering, Engineering, Transactions A: Basics, 36(4), 788-796. Available at: https: https://doi.org/10.5829/ije.2023.34.04a.15
Ikram, H. et. al. (2022). Additive manufacturing of smart polymeric composites: Literature review and future perspectives. Polymer Composites, 43(9), 6355-6380. Available at: https://doi.org/10.1002/pc.26948
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