Thermal induced shape-memory and self-healing of segmented polyurethane containing diselenide bonds

In vivo self-assembled shape-memory polyurethane for minimally invasive delivery and therapy

Advanced elastomers are highly in demand for the fabrication of medical devices for minimally invasive surgery (MIS). Herein, a shape memory and self-healing polyurethane (PCLUSe) composed of semi-crystalline poly(ε-caprolactone) (PCL) segments and interchangeable and antioxidative diselenide bonds was designed and synthesized. The excellent shape memory of PCLUSe contributed to the smooth MIS operation, leading to less surgical wounds than in the case of sternotomy. The diselenide bonds of PCLUSe contributed to the rapid self-healing under 405 nm irradiation within 60 s, and the alleviation of tissue oxidation post injury. After being delivered through a 10 mm diameter trocar onto a beating canine heart by MIS, two shape-recovered PCLUSe films self-assembled (self-healing) into a larger single patch (20 × 10 × 0.2 mm3) under the trigger of laser irradiation in situ, which could efficiently overcome the limited-size problem within MIS and meet a larger treatment area. The diselenide bonds in the PCLUSe cardiac patches protected the myocardium under oxidative stress post myocardial infarction (MI), and significantly maintained the cardiac functions.

Simple and Efficient Synthesis of Oligoetherdiamines: Hardeners of Epoxyurethane Oligomers for Obtaining Coatings with Shape Memory Effect

In this work, new polymers with a shape memory effect for self-healing coatings based on oligomers with terminal epoxy groups, synthesized from oligotetramethylene oxide dioles of various molecular weights, were developed. For this purpose, a simple and efficient method for the synthesis of oligoetherdiamines with a high yield of the product, close to 94%, was developed. Oligodiol was treated with acrylic acid in the presence of a catalyst, followed by the reaction of the reaction product with aminoethylpiperazine. This synthetic route can easily be upscaled. The resulting products can be used as hardeners for oligomers with terminal epoxy groups synthesized from cyclic and cycloaliphatic diisocyanates. The effect of the molecular weight of newly synthesized diamines on the thermal and mechanical properties of urethane-containing polymers has been studied. Elastomers synthesized from isophorone diisocyanate showed excellent shape fixity and shape recovery ratios of >95% and >94%, respectively.

Preparation and Closed-Loop Recycling of Ultra-High-Filled Wood Flour/Dynamic Polyurethane Composites

The development of biomass-based composites has greatly reduced the daily consumption of plastics. However, these materials are rarely recyclable, thus, posing a severe threat to the environment. Herein, we designed and prepared novel composite materials with ultra-high biomass (i.e., wood flour) filling capacity and good closed-loop recycling properties. The dynamic polyurethane polymer was polymerized in situ on the surface of wood fiber, and then they were hot-pressed into composites. Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), and dynamic thermomechanical analysis (DMA) measurements reveal good compatibility between the polyurethane and wood flour in the composites when the wood flour content is ≤80 wt%. The maximum tensile and bending strength of the composite are 37 and 33 MPa when the wood flour content is 80%. The higher wood flour content results in higher thermal expansion stability and creep resistance in the composites. Moreover, the thermal debonding of dynamic phenol–carbamate bonds facilitates the composites to undergo physical and chemical cycling. The recycled and remolded composites exhibit good mechanical property recovery rates and retain the chemical structures of the original composites.

Self-Healing Polymeric Soft Actuators

Natural evolution has provided multicellular organisms with sophisticated functionalities and repair mechanisms for surviving and preserve their functions after an injury and/or infection. In this context, biological systems have inspired material scientists over decades to design and fabricate both self-healing polymeric materials and soft actuators with remarkable performance. The latter are capable of modifying their shape in response to environmental changes, such as temperature, pH, light, electrical/magnetic field, chemical additives, etc. In this review, we focus on the fusion of both types of materials, affording new systems with the potential to revolutionize almost every aspect of our modern life, from healthcare to environmental remediation and energy. The integration of stimuli-triggered self-healing properties into polymeric soft actuators endow environmental friendliness, cost-saving, enhanced safety, and lifespan of functional materials. We discuss the details of the most remarkable examples of self-healing soft actuators that display a macroscopic movement under specific stimuli. The discussion includes key experimental data, potential limitations, and mechanistic insights. Finally, we include a general table providing at first glance information about the nature of the external stimuli, conditions for self-healing and actuation, key information about the driving forces behind both phenomena, and the most important features of the achieved movement.

Progress in Utilizing Dynamic Bonds to Fabricate Structurally Adaptive Self-Healing, Shape Memory, and Liquid Crystal Polymers

Stimuli-responsive structurally dynamic polymers are capable of mimicking the biological systems to adapt themselves to the surrounding environmental changes and subsequently exhibiting a wide range of responses ranging from self-healing to complex shape-morphing. Dynamic self-healing polymers (SHPs), shape-memory polymers (SMPs) and liquid crystal elastomers (LCEs), which are three representative examples of stimuli-responsive structurally dynamic polymers, have been attracting broad and growing interest in recent years because of their potential applications in the fields of electronic skin, sensors, soft robots, artificial muscles, and so on. We review recent advances and challenges in the developments towards dynamic SHPs, SMPs and LCEs, focusing on the chemistry strategies and the dynamic reaction mechanisms that enhance the performances of the materials including self-healing, reprocessing and reprogramming. We compare and discuss the different dynamic chemistries and their mechanisms on the enhanced functions of the materials, where three summary tables are presented: a library of dynamic bonds and the resulting characteristics of the materials. Finally, we provide a critical outline of the unresolved issues and future perspectives on the emerging developments. This article is protected by copyright. All rights reserved.

Shape Memory Composite Sandwich Structures with Self-Healing Properties

In this study, Polyurea/Formaldehyde (PUF) microcapsules containing Dicyclopentadiene (DCPD) as a healing substance were fabricated in situ and mixed at relatively low concentrations (<2 wt%) with a thermosetting polyurethane (PU) foam used in turn as the core of a sandwich structure. The shape memory (SM) effect depended on the combination of the behavior of the PU foam core and the shape memory polymer composite (SMPC) laminate skins. SMPC laminates were manufactured by moulding commercial carbon fiber-reinforced (CFR) prepregs with a SM polymer interlayer. At first, PU foam samples, with and without microcapsules, were mechanically tested. After, PU foam was inserted into the SMPC sandwich structure. Damage tests were carried out by compression and bending to deform and break the PU foam cells, and then assess the structure self-healing (SH) and recovery capabilities. Both SM and SH responses were rapid and thermally activated (120 °C). The CFR-SMPC skins and the PU foam core enable the sandwich to exhibit excellent SM properties with a shape recovery ratio up to 99% (initial configuration recovery). Moreover, the integration of microcapsules (0.5 wt%) enables SH functionality with a structural restoration up to 98%. This simple process makes this sandwich structure ideal for different industrial applications.

Organoselenium chemistry-based polymer synthesis

Novel synthesis of selenium containing polymers with pre-determined structures and applications thereof.