High performance bio-based polyurethane elastomers: Effect of different soft and hard segments

Heating/Solvent Responsive Shape-Memory Polymers for Implant Biomedical Devices in Minimally Invasive Surgery: Current Status and Challenge

This review is about the fundamentals and practical issues in applying both heating and solvent responsive shape memory polymers (SMPs) for implant biomedical devices via minimally invasive surgery. After revealing the general requirements in the design of biomedical devices based on SMPs and the fundamentals for the shape-memory effect in SMPs, the underlying mechanisms, characterization methods, and several representative biomedical applications, including vascular stents, tissue scaffolds, occlusion devices, drug delivery systems, and the current R&D status of them, are discussed. The new opportunities arising from emerging technologies, such as 3D printing, and new materials, such as vitrimer, are also highlighted. Finally, the major challenge that limits the practical clinical applications of SMPs at present is addressed.

Bio-based, biodegradable and amorphous polyurethanes with shape memory behavior at body temperature

In this work, a series of bio-based, biodegradable and amorphous shape memory polyurethanes were synthesized by a two-step pre-polymerization process from polylactide (PLA) diol, polycaprolactone (PCL) diol and diphenylmethane diisocyanate-50 (MDI-50). The ratio of PLA diol to PCL diol was adjusted to investigate their thermal and mechanical properties. These bio-based shape memory polyurethanes (bio-PUs) showed a glass transition temperature (T_g) value in the range of −10.7–32.5 °C, which can be adjusted to be close to body temperature. The tensile strength and elongation of the bio-PUs could be tuned in the range from 1.7 MPa to 12.9 MPa and from 767.5% to 1345.7%, respectively. Through a series of shape memory tests, these bio-PUs exhibited good shape memory behavior at body temperature. Among them, PU with 2 : 1 as the PLA/PCL ratio showed the best shape recovery behavior with a shape recovery rate higher than 98% and could fully reach the original shape state in 15 s at 37 °C. Therefore, these shape memory bio-PUs are promising for applications in smart biomedical devices.

A series of bio-based, biodegradable and amorphous polyurethanes with shape memory behavior at body temperature were synthesized.

Fabric Coated with Shape Memory Polyurethane and Its Properties

In order to provide thermo-physiological comfort to the wearer, textile materials should have some functional property like water-resistance or water vapor transmission (WVT), so that perspiration can evaporate and be transmitted from the body surface to the environment even in extreme weather conditions that require wind and rain proof. Shape memory polyurethane (SMPU) could possibly be a candidate; it is a functional textile material that meets such requirements. In this research, we synthesized a series of SMPUs, which are responsive materials, to test whether these coated cotton fabrics could provide thermal insulation with lower permeability at low temperature or low relative humidity (RH), and high permeability at room temperature or above, or high relative humidity with its water-resistance property. In this paper, we have proposed a segmented shape memory polyurethane for coated textiles in order to have a water-resistant textile with good water vapor transmitting ability.

Facile Preparation of Highly Stretchable and Recovery Peptide-Polyurethane/Ureas

In this work, a new class of highly stretchable peptide-polyurethane/ureas (PUUs) were synthesized containing short β-sheet forming peptide blocks of poly(γ-benzyl-l-glutamate)-b-poly(propylene glycol)-b-poly(γ-benzyl-l-glutamate) (PBLG-b-PPG-b-PBLG), isophorone diisocyanate as the hard segment, and polytetramethylene ether glycol as the soft phase. PBLG-b-PPG-b-PBLG with short peptide segment length (<10 residues) was synthesized by amine-initiated ring opening polymerization of γ-benzyl-l-glutamate-N-carboxyanhydrides (BLG-NCA), which shows mixed α-helix and β-sheet conformation, where the percent of β-sheet structure was above 48%. Morphological studies indicate that the obtained PUUs show β-sheet crystal and nanofibrous structure. Mechanical tests reveal the PUUs display medium tensile strength (0.25⁻4.6 MPa), high stretchability (>1600%), human-tissue-compatible Young's modulus (226⁻513 KPa). Furthermore, the shape recovery ratio could reach above 85% during successive cycles at high strain (500%). In this study, we report a facile synthetic method to obtain highly stretchable and recovery peptide-polyurethane/urea materials, which will have various potential applications such as wearable and implantable electronics, and biomedical devices.

Review of Progress in Shape Memory Epoxies and Their Composites

Shape memory polymer (SMP) is capable of memorizing one or more temporary shapes and recovering successively to the permanent shape upon various external stimuli. Beside of the above mentioned one-way variants, also two-way shape memory polymers (SMPs) and shape memory (SM) systems exist which feature a reversible shape change on the basis of "on-off switching" of the external stimulus. The preparation, properties and modelling of shape memory epoxy resins (SMEP), SMEP foams and composites have been surveyed in this exhaustive review article. The underlying mechanisms and characteristics of SM were introduced. Emphasis was put to show new strategies on how to tailor the network architecture and morphology of EPs to improve their SM performance. To produce SMEPs novel preparation techniques, such as electrospinning, ink printing, solid-state foaming, were tried. The potential of SMEPs and related systems as multifunctional materials has been underlined. Added functionality may include, among others, self-healing, sensing, actuation, porosity control, recycling. Recent developments in the modelling of SMEPs were also highlighted. Based on the recent developments some open topics were deduced which are merit of investigations in future works.

Bio-based (co)polylactide-urethane networks with shape memory behavior at body temperature

The novel bio-based polymer networks with shape memory behavior were synthesized from polylactide-based tetraols and hexamethylene diisocyanate trimer.