Fabric Coated with Shape Memory Polyurethane and Its Properties

Redefining vascular repair: revealing cellular responses on PEUU-gelatin electrospun vascular grafts for endothelialization and immune responses on in vitro models

Tissue-engineered vascular grafts (TEVGs) poised for regenerative applications are central to effective vascular repair, with their efficacy being significantly influenced by scaffold architecture and the strategic distribution of bioactive molecules either embedded within the scaffold or elicited from responsive tissues. Despite substantial advancements over recent decades, a thorough understanding of the critical cellular dynamics for clinical success remains to be fully elucidated. Graft failure, often ascribed to thrombogenesis, intimal hyperplasia, or calcification, is predominantly linked to improperly modulated inflammatory reactions. The orchestrated behavior of repopulating cells is crucial for both initial endothelialization and the subsequent differentiation of vascular wall stem cells into functional phenotypes. This necessitates the TEVG to provide an optimal milieu wherein immune cells can promote early angiogenesis and cell recruitment, all while averting persistent inflammation. In this study, we present an innovative TEVG designed to enhance cellular responses by integrating a physicochemical gradient through a multilayered structure utilizing synthetic (poly (ester urethane urea), PEUU) and natural polymers (Gelatin B), thereby modulating inflammatory reactions. The luminal surface is functionalized with a four-arm polyethylene glycol (P4A) to mitigate thrombogenesis, while the incorporation of adhesive peptides (RGD/SV) fosters the adhesion and maturation of functional endothelial cells. The resultant multilayered TEVG, with a diameter of 3.0 cm and a length of 11 cm, exhibits differential porosity along its layers and mechanical properties commensurate with those of native porcine carotid arteries. Analyses indicate high biocompatibility and low thrombogenicity while enabling luminal endothelialization and functional phenotypic behavior, thus limiting inflammation in in-vitro models. The vascular wall demonstrated low immunogenicity with an initial acute inflammatory phase, transitioning towards a pro-regenerative M2 macrophage-predominant phase. These findings underscore the potential of the designed TEVG in inducing favorable immunomodulatory and pro-regenerative environments, thus holding promise for future clinical applications in vascular tissue engineering.

Advances in Additive Manufacturing of Polymer-Fused Deposition Modeling on Textiles: From 3D Printing to Innovative 4D Printing-A Review

Technological advances and the development of new and advanced materials allow the transition from three-dimensional (3D) printing to the innovation of four-dimensional (4D) printing. 3D printing is the process of precisely creating objects with complex shapes by depositing superimposed layers of material. Current 3D printing technology allows two or more filaments of different polymeric materials to be placed, which, together with the development of intelligent materials that change shape over time or under the action of an external stimulus, allow us to innovate and move toward an emerging area of research, innovative 4D printing technology. 4D printing makes it possible to manufacture actuators and sensors for various technological applications. Its most significant development is currently in the manufacture of intelligent textiles. The potential of 4D printing lies in modular manufacturing, where fabric-printed material interaction enables the creation of bio-inspired and biomimetic devices. The central part of this review summarizes the effect of the primary external stimuli on 4D textile materials, followed by the leading applications. Shape memory polymers attract current and potential opportunities in the textile industry to develop smart clothing for protection against extreme environments, auxiliary prostheses, smart splints or orthoses to assist the muscles in their medical recovery, and comfort devices. In the future, intelligent textiles will perform much more demanding roles, thus envisioning the application fields of 4D printing in the next decade.

Investigation of Shape Memory Polyurethane Properties in Cold Programming Process Towards Its Applications

Thermoresponsive shape memory polymers (SMPs) with the remarkable ability to remember a temporary shape and recover their original one using temperature have been gaining more and more attention in a wide range of applications. Traditionally, SMPs are investigated using a method named often "hot-programming", since they are heated above their glass transition temperature (Tg) and after that, reshaped and cooled below Tg to achieve and fix the desired configuration. Upon reheating, these materials return to their original shape. However, the heating of SMPs above their Tg during a thermomechanical cycle to trigger a change in their shape creates a temperature gradient within the material structure and causes significant thermal expansion of the polymer sample resulting in a reduction in its shape recovery property. These phenomena, in turn, limit the application fields of SMPs, in which fast actuation, dimensional stability and low thermal expansion coefficient are crucial. This paper aims at a comprehensive experimental investigation of thermoplastic polyurethane shape memory polymer (PU-SMP) using the cold programming approach, in which the deformation of the SMP into the programmed shape is conducted at temperatures below Tg. The PU-SMP glass transition temperature equals approximately 65 °C. Structural, mechanical and thermomechanical characterization was performed, and the results on the identification of functional properties of PU-SMPs in quite a large strain range beyond yield limit were obtained. The average shape fixity ratio of the PU-SMP at room temperature programming was found to be approximately 90%, while the average shape fixity ratio at 45 °C (Tg - 20 °C) was approximately 97%. Whereas, the average shape recovery ratio was 93% at room temperature programming and it was equal to approximately 90% at 45 °C. However, the results obtained using the traditional method, the so-called hot programming at 65 °C, indicate a higher shape fixity value of 98%, but a lower shape recovery of 90%. Thus, the obtained results confirmed good shape memory properties of the PU-SMPs at a large strain range at various temperatures. Furthermore, the experiments conducted at both temperatures below Tg demonstrated that cold programming can be successfully applied to PU-SMPs with a relatively high Tg. Knowledge of the PU-SMP shape memory and shape fixity properties, estimated without risk of material degradation, caused by heating above Tg, makes them attractive for various applications, e.g., in electronic components, aircraft or aerospace structures.

Sunlight-Driven Photocatalytic Active Fabrics through Immobilization of Functionalized Doped Titania Nanoparticles

Frequent washing of textiles poses a serious hazard to the ecosystem, owing to the discharge of harmful effluents and the release of microfibers. On one side, the harmful effluents from detergents are endangering marine biota, while on the other end, microplastics are observed even in breastfeeding milk. This work proposes the development of sunlight-driven cleaning and antibacterial comfort fabrics by immobilizing functionalized Zn-doped TiO₂ nanoparticles. The research was implemented to limit the use of various detergents and chemicals for stain removal. A facile sol-gel method has opted for the fabrication of pristine and Zn-doped TiO₂ nanoparticles at three different mole percentages of Zn. The nanoparticles were successfully functionalized and immobilized on cotton fabric using silane coupling agents via pad-dry-cure treatment. As-obtained fabrics were characterized by their surface morphologies, availability of chemical functionalities, and crystallinity. The sunlight-assisted degradation potential of as-functionalized fabrics was evaluated against selected pollutants (eight commercial dyes). The 95-98% degradation of dyes from the functionalized fabric surface was achieved within 3 h of sunlight exposure, estimated by color strength analysis with an equivalent exposition of bactericidal activities. The treated fabrics also preserved their comfort and mechanical properties. The radical trapping experiment was performed to confirm the key radicals responsible for dye degradation, and h⁺ ions were found to be the most influencing species. The reaction pathway followed the first order kinetic model with rate constant values of 0.0087 min^-1 and 0.0131 min^-1 for MB and MO dyes, respectively.

"Evaluation of physico-mechanical properties of naturally dyed betel-nut leaf plate (BLPF) - Banana blended fabric"

Betel-nut leaf plate fiber (BLPF) is a lingo-cellulosic natural fiber that can be used to make eco-friendly and biodegradable blended or hybrid fabric with Banana fiber. In the world of organic textiles, naturally dyed BLPF-Banana fiber can be used for wearable products and satisfy health and hygiene issues. BLPF and Banana fiber can be good natural fibers for hybrid fabrics despite being considered waste materials. In this research work, both of the fibers were pretreated carefully to get the desired fineness, color, flexibilities, etc., which are necessary to manufacture fabric. BLPF-Banana woven (1 × 1) hybrid fabric was developed where 12 Ne Banana yarns were used in the warp direction, and 20 Ne BLPF yarns were used in the weft direction and it was dyed naturally with Turmeric. Evaluations of different physico-mechanical properties; tensile strength (854.9 N), tearing strength (14.5 N), stiffness (3.1 N), crease recovery (75° angle), and fabric thickness (1.33 mm) of naturally dyed BLPF-Banana blended fabric were tested, and found satisfactory. SEM, FTIR, and Water vapor transmission tests were also conducted in this study. It attempted to turn the wastages into an asset to make a unique biodegradable BLPF-Banana hybrid fabric by blending two types of natural fibers with the help of natural dyeing substance; it could be a god replacement for synthetic blended fabric.

Effect of Aromatic Chain Extenders on Polyurea and Polyurethane Coatings Designed for Defense Applications

The present work describes the synthesis of new versatile polyurea (PU) and polyurethane (PUR) matrices, including different chain extenders, which facilitate the design of distinct, tunable properties, and high-performance derivatives. These polymers can be used for various defense and security applications, such as coatings for ballistic protection, CBRN protection, binders for energetic formulations, etc. Combining aliphatic and aromatic molecules in PU or PUR structures enables the synthesis of polymers with improved and controllable thermo-mechanical properties. Thus, for polyurea synthesis, we utilized two types of polymeric aliphatic diamines and three types of aromatic chain extenders (1,1'-biphenyl-4,4'-diamine, benzene-1,2-diamine, and 1,2-diphenylhydrazine). An analogous method was used to synthesize polyurethane films by employing one polymeric aliphatic polyol and three types of aromatic chain extenders (benzene-1,3-diol, benzene-1,4-diol, and benzene-1,2,3-triol). Subsequently, various analytic techniques (Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), single cantilever dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), frequency-dependent shear modulus survey, tensile tests, water contact angle measurements, and scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDX)) have been utilized to characterize the synthesized materials and to evaluate the influence of each chain extender on their final properties.

Application and Development of Shape Memory Micro/Nano Patterns

Shape memory polymers (SMPs) are a class of smart materials that change shape when stimulated by environmental stimuli. Different from the shape memory effect at the macro level, the introduction of micro-patterning technology into SMPs strengthens the exploration of the shape memory effect at the micro/nano level. The emergence of shape memory micro/nano patterns provides a new direction for the future development of smart polymers, and their applications in the fields of biomedicine/textile/micro-optics/adhesives show huge potential. In this review, the authors introduce the types of shape memory micro/nano patterns, summarize the preparation methods, then explore the imminent and potential applications in various fields. In the end, their shortcomings and future development direction are also proposed.

Actuator Behaviour of Tailored Poly(thiourethane) Shape Memory Thermosets

In this work, a new family of poly(thiourethane) shape memory thermosetting actuators was developed and characterized. These materials can be easily prepared from mixtures of two different aliphatic diisocyanates and a trithiol in the presence of a latent catalyst, allowing an easy manipulation of the formulation. Rheological studies of the curing process confirm the latent character of the formulations. The glass transition temperatures and the mechanical properties can be modified by varying the proportion of diisocyanates (hexamethylene diisocyanate, HDI, and isophorone diisocyanate, IPDI) with stoichiometric amounts of trimethylolpropane tris(3-mercaptopropionate). The shape-memory behavior was deeply investigated under three different conditions: unconstrained, partially constrained, and fully constrained. Tests were performed in single cantilever bending mode to simulate conditions closer to real complex mechanics of thermomechanical actuators under flexural performances. The complex recovery process in single cantilever bending mode was compared with that obtained using tensile mode. The results evidenced that the amount of recovery force in fully constrained conditions, or energy released during the recovery process in partially constrained, can be modulated by simply changing the proportion of both diisocyanates. A simple model based on Timoshenko beam theory was used for the prediction of the amount of work performed. The reported results are an important guideline to design shape-memory materials based on poly(thiourethane) networks, establishing criteria for the choice of the material depending on the expected application.

Hot-melt Adhesive Bonding of Polyurethane/Fluorinated Polyurethane/Alkylsilane-Functionalized Graphene Nanofibrous Fabrics with Enhanced Waterproofness, Breathability, and Mechanical Properties

Waterproof-breathable (WB) materials with outstanding waterproofness, breathability, and mechanical performance are critical in diverse consumer applications. Electrospun nanofibrous membranes with thin fiber diameters, small pore sizes, and high porosity have attracted significant attention in the WB fabric field. Hot-press treatment technology can induce the formation of inter-fiber fusion structures and hence improve the waterproofness and mechanical performance. By combining electrospinning and hot-press treatment technology, polyurethane/fluorinated polyurethane/thermoplastic polyurethane/alkylsilane-functionalized graphene (PU/FPU/TPU/FG) nanofiber WB fabric was fabricated. Subsequently, the morphologies, porous structure, hydrostatic pressure, water vapor transmission rate (WVTR), and stress–strain behavior of the nanofiber WB fabric were systematically investigated. The introduction of the hydrophobic FG sheet structure and the formation of the inter-fiber fusion structure greatly improved not only the waterproofness but also the mechanical performance of the nanofiber WB fabric. The optimized PU/FPU/TPU-50/FG-1.5 WB fabric exhibited an excellent comprehensive performance: a high hydrostatic pressure of 80.4 kPa, a modest WVTR of 7.6 kg m⁻² d⁻¹, and a robust tensile stress of 127.59 MPa, which could be used to achieve various applications. This work not only highlights the preparation of materials, but also provides a high-performance nanofiber WB fabric with huge potential application prospects in various fields.

Mechanically Robust, Responsive Composite Membrane for a Thermoregulating Textile

The human body releases heat via four mechanisms: conduction, convection, evaporation, and radiation. The normal core temperature of the human body is around 37 °C, and metabolism may be negatively affected and enzymes/proteins may be destroyed if the core temperature rises above 45 °C. To prevent such overheating, we developed an evaporative-radiative-convective fabric which can control the personal microclimate of the human body through a cooling mechanism (evaporation of perspiration, air convection, and emission of heat radiation directly into the environment). In this work, we fabricated a thermo-moisture sensitive polyurethane/silica aerogel composite membrane which showed super evaporative and radiative effects and which can facilitate the convection process in the human body. We also fabricated a sensitive membrane-based textile which can cool down the human body by releasing body heat. The developed material possessed robust mechanical properties for the longevity of the material, high water-evaporative ability, and air permeability to provide comfort to the wearer. Microclimate-controlled clothing can release most of our body heat to the environment.

Shape Memory Polyurethane and its Composites for Various Applications

The inherent capability to deform and reform in a predefined environment is a unique property existing in shape memory polyurethane. The intrinsic shape memory ability of the polyurethane is due to the presence of macro domains of soft and hard segments in its bulk, which make this material a potential candidate for several applications. This review is focused on manifesting the applicability of shape memory polyurethane and its composites/blends in various domains, especially to human health such as shielding of electromagnetic interference, medical bandage development, bone tissue engineering, self-healing, implants development, etc. A coherent literature review highlighting the prospects of shape memory polyurethane in versatile applications has been presented.