Much attention has been drawn to our previously reported polyurethane featuring a hard backbone and dangling poly(ethylene glycol) (PEG) soft segment. It is endowed with a unique self-stiffening property when exposed to water. Yet the mechanism from a molecular perspective is still not quite clear. Herein, coarse-grained (CG) and all-atom (AA) molecular dynamics (MD) simulations, alongside experimental approaches, have been employed to unravel the mechanism behind the phenomenon. It is confirmed that water could induce the polyurethane to achieve a higher degree of phase separation. When being stretched, hard domains of aqueous side chain PEG polyurethane (SPPU) have a stronger tendency to orient in the direction of tensile stress and facilitate the effective transfer of stress. This enhancement effect of water-stiffening cannot be achieved at an insufficient side chain density. The ratio of hydrogen bonds in the SPPU exhibited a higher degree of enhancement with water content, which is in accordance with experimental results. The unique topology of SPPU was considered to be the most important factor to the Young's modulus determined by the gradient boosting regression (GBR) model. This research helps to advance our comprehension of the interplay between the structure and performance of polyurethane, providing a theoretical foundation for the design of a novel material.

Synthesis biomedical waterborne polyurethane with high strength retention and satisfactory water absorption by a solvent free method.

The reported dynamic covalent bonds (DCBs) exhibit certain drawbacks, including sluggish reaction rates and high dissociation temperatures, which impede the reusability of DCBs cross-linked polymers. Herein, we develop a kind of imidazole-urea bond (IUBs) through the rapid self-catalytic reaction between imidazole and isocyanate without additional catalysts. The IUBs are found to be highly reversible via a thermally dissociative mechanism while also demonstrating an irreversible exchange with amines. Then, histamine (1H-imidazole-4-ethanamine) is first employed as a chain extender to construct IUBs in the synthesis of novel imidazole-based cross-linked polyurethane-ureas (IMCPU). The IMCPU can undergo multiple recyclings of melt processing and be aminolyzed even at room temperature. Given the wide availability of the commodity histamine, IMCPU exhibits great potential for broad applications in the fields of dynamic materials.

Despite the rapid development of tissue adhesives, flaws including allergies, poor stability, and indiscriminate double-sided adhesive properties limit their application in the medical field. In this work, Janus polyurethane patches were spontaneously prepared by adjusting the difference in the functional group distribution between the top and bottom sides of the patch during emulsion drying. Consequently, poor adhesion was exhibited on the bottom surface, while the top surface can easily adhere to metals, polymers, glasses, and tissues. The difference in adhesive strength to pork skin between the two surfaces is more than 5 times. The quaternary ammonium salt and hydrophilic components on the surface of the polyurethane patch enable the rapid removal and absorption of water from the tissue surface to achieve wet adhesion. Animal experiments have demonstrated that this multifunctional Janus polyurethane patch can promote skin wound closure and healing of infected wounds. This facile and effective strategy to construct Janus polyurethane patch provides a promising method for the development of functional tissue-adhesives.

Ice-templated porous biomaterials possess transformative potential in regenerative medicine; yet, scaling up ice-templating processes for broader applications-owing to inconsistent pore formation-remains challenging. This study reports an innovative semi-solid freeze-casting technique that draws inspiration from semi-solid metal processing (SSMP) combined with ice cream-production routines. This versatile approach allows for the large-scale assembly of various materials, from polymers to inorganic particles, into isotropic 3D scaffolds featuring uniformly equiaxed pores throughout the centimeter scale. Through (cryo-)electron microscopy, X-ray tomography, and finite element modeling, the structural evolution of ice grains/pores is elucidated, demonstrating how the method increases the initial ice nucleus density by pre-fabricating a semi-frozen slurry, which facilitates a transition from columnar to equiaxed grain structures. For a practical demonstration, as-prepared scaffolds are integrated into a bilayer tissue patch using biodegradable waterborne polyurethane (WPU) for large-scale oral mucosal reconstruction in minipigs. Systematic analyses, including histology and RNA sequencing, prove that the patch modulates the healing process toward near-scarless mucosal remodeling via innate and adaptive immunomodulation and activation of pro-healing genes converging on matrix synthesis and epithelialization. This study not only advances the field of ice-templating fabrication but sets a promising precedent for scaffold-based large-scale tissue regeneration. A generic semi-solid freeze-casting technique is established, resulting from an elegant coupling of semi-solid metal processing and ice cream. This novel method enables the scalable fabrication of homogeneous, isotropic porous scaffolds for large-scale oral mucosal defect repair. Biomaterial-mediated scar-free mucosal remodeling arises from early wound contracture blocking, caused by innate and adaptive immunomodulation together with comprehensive activation of pro-healing signaling. image

Injectable hydrogels have attracted significant interest in the biomedical field due to their minimal invasiveness and accommodation of intricate scenes. Herein, we developed an injectable polyurethane-based thermogel platform by modulating the hydrophilic-hydrophobic balance of the segmented components with pendant PEG. The thermogelling behavior is achieved by a combination of the bridging from the hydrophilic PEG and the percolated network from the hydrophobic micelle core. Firstly, the thermogelation mechanism of this system was demonstrated by both DPD simulation and experimental investigation. The gelling temperature could be modulated by varying the solid content, the component of soft segments, and the length of the pendant PEG. We further applied 3D printing technology to prepare personalized hydrogel structures. This integration highlights the adaptability of our thermogel for fabricating complex and patient-specific constructs, presenting a significant advance in the field of regenerative medicine and tissue engineering. Subsequently, in vitro cell experiments demonstrated that the thermogel had good cell compatibility and could promote the proliferation and migration of L929 cells. Impressively, A549 cells could be expediently in situ parceled in the thermogel for three-dimensional cultivation and gain lifeful 3D cell spheres after 7 days. Further, in vivo experiments demonstrated that the thermogel could promote wound healing with the regeneration of capillaries and hair follicles. Ultimately, our study demonstrates the potential of hydrogels to prepare personalized hydrogel structures via 3D printing technology, offering innovative solutions for complex biomedical applications. This work not only provides a fresh perspective for the design of injectable thermogels but also offers a promising avenue to develop thermoresponsive waterborne polyurethane for various medical applications. This study introduces an injectable polyurethane thermogel with tunable transition temperature via hydrophilic-hydrophobic balance, enabling rapid gelation, injectability, biodegradation, and significantly improved wound healing.

Although conventional chemical copolymerization method has shown favorable results in improving certain performance of polymers, simultaneous improvement of overall properties is hardly achieved. Here, we reported a feasible method to fabricate high-performance polymers with great overall properties by simultaneously tailoring their chemical constitution and topological conformation. We designed and synthesized a novel functional monomer with a sidechain caged structure based on phosphorus chemistry, and prepared the corresponding aliphatic polyamide as a typical representative of thermoplastic synthetic polymers. The incorporation of a sidechain caged structure enhanced the chain entanglement of the resultant polyamide, thus improved the mechanical strength by 39% and largely enhanced the heat resistance. The great processability was basically uninfluenced due to the easy dissociation of the entanglement during processing, enabling the potentially wide application fields as both fibers and engineering plastics. Furthermore, based on the free radical scavenging effect of the phosphorus-based monomer, the flame retardancy of the resultant polyamide was significantly improved. In sight of these findings, this work provides a novel method for fabricating high-performance polymers for various applications.

Temperature-accelerated in vitro degradation was established to estimate the longevity of polyurethane applied for long-term implantation. However, the prediction did not correlate well with the data from clinical explants and the rationality of accelerated in vitro test is still in a controversial due to the deviation. To improve the accuracy of the in vitro prediction, the influence of hydrogen bonding (HB) on the accelerated hydrolysis of silicone based polyetherurethans (SPEUs) extended with three side chains. Combining the temperature-controlled FTIR and the physical properties after temperature-accelerated in vitro degradation, it was demonstrated that side chain could increase the degree of hydrogen bond dissociation at higher temperature, resulting in the decrease of the calculated activation energy (Ea) of hydrolysis. At low temperatures, changes in surface morphology and molar mass of PEUs are minimal and HB are less easily dissociated, which had barely impact on the hydrolysis resistance. It was proposed that the Ea will not be impacted and that the accuracy of prediction will be increased if the acceleration temperature is lower than 70 °C and HB change is less than 15

The ability of nanocarriers to enter tumor cells can be enhanced by positive surface charge. Nonetheless, the relationship between the spatial distributions of cationic groups and the endocytosis and tumor penetration of nanocarriers remains largely elusive. Here, using quaternary ammonium salt (QAS) as a model cationic group, a series of hybrid micelles (HMs) bearing QAS with different spatial distributions were prepared from star-shaped polymers with well-defined molecular architectures. The structural characteristics of HM, such as spatial location of QAS and local poly(ethylene glycol) (PEG) density near QAS, were investigated by both experimental techniques and dissipative particle dynamics (DPD) simulation. We show that the drug carriers with QAS extending to the micellar outer space allows QAS to facilitate cell surface binding with minimized hindrance, resulting in greatly enhanced endocytosis compared with nanocarriers with QAS attached onto the micellar surface or shielded by a PEG corona. This study offers cues for future development of tumor-penetrating drug delivery systems.

Volatile solid additives (SADs) are considered as a simple yet effective approach to tune the film morphology for high-performance organic solar cells (OSCs). However, the structural effects of the SADs on the photovoltaic performance are still elusive. Herein, two volatilizable SADs were designed and synthesized. One is SAD1 with twisted conformation, while the other one is planar SAD2 with the S···O noncovalent intramolecular interactions (NIIs). The theoretical and experimental results revealed that the planar SAD2 with smaller space occupation can more easily insert between the Y6 molecules, which is beneficial to form a tighter intermolecular packing mode of Y6 after thermal treatment. As a result, the SAD2-treated OSCs exhibited less recombination loss, more balanced charge mobility, higher hole transfer rate, and more favorable morphology, resulting in a record power conversion efficiency (PCE) of 18.85% (certified PCE: 18.7%) for single-junction binary OSCs. The universality of this study shed light on understanding the conformation effects of SADs on photovoltaic performances of OSCs.

To regulate the phase structure and improve the chemical resistance of silicon-containing polycarbonate urethanes (SiPCUs), a diol with fluorocarbon side chain was introduced as a second chain extender. The fluorinated silicon-containing polyurethanes (FSiPCUs) displayed stronger hydrogen bonding between carbonate and urethane groups than SiPCUs in attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The glass transition temperatures of the polycarbonate soft segments shifted to higher temperatures determined by thermal analysis. Combined with the results of small angle X-ray scattering (SAXS) and dissipative particle dynamics (DPD), it was proved that the dangling chain could disrupt the undesirable excessive hard segment aggregation caused by the apolar PDMS and promoted the miscibility between hard segments and polycarbonate soft segments. The enhanced segmental interaction provided protection for the vulnerable carbonate groups from chain scission initiated by oxidative media.

Shape memory polymers (SMPs) with multiple functionalities have great potential in implantable biomedical devices, especially vascular stents. However, stents made of SMPs are generally faced with the problem of insufficient radial support due to the sharp decline of the modulus after shape recovery. Therefore, it is necessary to improve the modulus of SMPs after opening the narrow part by other means. In this study, the novel SMPs available for vascular stents were developed with impressive water-induced stiffening when shape recovered in a physiological environment. Herein, a series of shape memory polyurethanes (SMPUs) containing full hard segments on the main chains and bearing hydrophilic tertiary amine soft segments on the side chains were synthesized. When immersed in water, the soft segments were dramatically separated from the hard segments, which were aggregated more to form densely packed hard domains with stronger hydrogen bonding and higher crystallinity. Both Young's modulus and the shape recovery ratio were thus promoted due to the segmental rearrangement in water. At the same time, hydrophilic side chains migrated to the surface driven by the segmental rearrangement in water, which promotes the adhesion and growth of vascular endothelial cells and inhibits the activation of the coagulation system. The ingenious structural design provided SMPUs with adequate mechanical strength and hemocompatibility to qualify for potential applications in self-expanding vascular stents.

Background The main challenge of polymeric micelles as drug delivery systems is that the actual delivery efficiency is not as high as expected, which is closely related with the interactions with the complex biological environments such as blood components, phagocytosis, and biodistribution. Herein, we expect to understand these concerns for the clinically relevant micelles that composed of methoxypolyethylene glycol (MPEG) with identical chain length And poly(ε-caprolactone) (PCL) with tunable chain length (PCLn-MPEG) (n=20, 30, and 40) wherein doxorubicin was encapsulated as a model drug. Methods The doxorubicin-loaded PCLn-MPEG micelles were prepared by a dialysis method and characterized by dynamic light scattering and transmission electron microscopy. The surface PEG density and chain conformation were investigated by dissipative particle dynamics simulation. The stability of the micelles was detected by nanoparticle tracking analysis. The effects of PCL chain length on the blood components, phagocytosis, and biodistribution were assayed in vitro and in vivo. Results The micelles exhibited spherical morphology with a diameter about 30nm. The PEG chain conformation from “mushroom-like” to “brush-like” was evident. The micelles have no remarkable effect on the red blood cells, blood coagulation, and platelet activation. Interestingly, the protein adsorption was affected and dependent on the chain conformation, with lowest adsorption for PCL30-MPEG, which also has the loWest phagocytosis. The stability of the micelles was in the order of PCL40-MPEG>PCL30-MPEG>PCL20-MPEG which was dependent on the PCL chain length. The micelles mainly accumulated in liver, with the order consistent with their stability, indicating that, besides the phagocytosis, the stability of the micelle plays an important role in biodistribution as well. The related mechanisms were proposed and discussed. Conclusion Manipulating the PEG/PCL ratio of the micelle is an effective approach to modulate the protein adsorption, phagocytosis, and biodistribution, which may be a prerequisite for clinical applications.

Fluorinated diols (FDO) with dangling chain were introduced into polyether urethanes (PEUs) as chain extender in order to achieve internal plasticization. Based on temperature dependent Fourier transform infrared (FTIR) spectroscopy results, the fluorinated polyether urethanes (FPEUs) exhibited weaker hydrogen bonding between C=O and N-H groups with addition of FDO. The crystallinity of hard domain was destroyed determined by thermal analysis. Combined with the results of dynamic mechanical analysis (DMA) and dissipative particle dynamics (DPD) simulation, it was proved that more loosely aggregated hard domains with weakened interaction separated from soft segment were formed. Rheological analysis indicated that FDO reduced the complex viscosity and viscous flow activation energy which endowed the polymer with more flexibility. Despite the loss of hydrogen bonds, there was no significant decline in mechanical property resulting from the decrease of hard segment dissolved in soft segment phase. The presence of fluorinated carbon side chain could function as internal plasticizer and contribute to the processability of polyurethane.

Shape-memory polymers (SMPs) induced by heat or water are commonly used candidates for biomedical applications. Shape recovery inevitably leads to a dramatic decrease of Young's modulus due to the enhanced flexibility of polymer chains at the transition temperature. Herein, the principle of phase-transition-induced stiffening of shape-memory metallic alloys (SMAs) is introduced to the design of molecular structures for shape-memory polyurethane (SMPUs), featuring all-hard segments composed of main chains that are attached with poly(ethylene glycol) (PEG) dangling side chains. Different from conventional SMPs, they achieve a soft-to-stiff transition when shape recovers. The stiffening process is driven by water-triggered segmental rearrangement due to the incompatibility between the hard segments and the soft PEG segments. Upon hydration, the extent of microphase separation is enhanced and the hard domains are transformed to a more continuous morphology to realize more effective stress transfer. Meanwhile, such segmental rearrangement facilitates the shape-recovery process in the hydrated state despite the final increased glass transition temperature (Tg ). This work represents a novel paradigm of simultaneously integrating balanced mechanics, shape-memory property, and biocompatibility for SMPUs as materials for minimally invasive surgery such as endoluminal stents.

Polydimethylsiloxane(PDMS) based segmented polyether urethanes (SiPEUs) suffer from poor adhesion between apolar PDMS and polar hard domains, which results in inferior mechanical properties and inadequate stability in long-term implantation. To regulate the interfacial miscibility, three chain extenders attached with different dangling side chains (fluorinated diol FDO, silicone-based diol SDO, and hexyl-based diol HDO) were used in two-step synthesis to modify the polarity of hard segments. Thermal analysis demonstrated a higher glass transition temperature of PDMS and PTMO (poly (tetramethylene oxide)) domain in SDO modified SiPEU(SSPEU) in contrast to the samples extended with FDO and HDO. Fourier transform infrared spectroscopy (FT-IR), small-angel x-ray scattering (SAXS), and dissipative particle dynamics (DPD) simulation further proved that SSPEU was achieved with optimal interfacial miscibility compared with SPEU. The intermediate layers were proposed to be functionally percolated composed of PDMS, PTMO, MDI-SDO, and MDI-BDO units, which promoted oxidative stability under accelerated test in vitro without mechanical compromise.