Microporous Hyper-Crosslinked Polystyrenes and Nanocomposites with High Adsorption Properties: A Review

Hyper-crosslinked (HCL) polystyrenes show outstanding properties, such as high specific surface area and adsorption capability. Several researches have been recently focused on tailoring their performance for specific applications, such as gas adsorption and separation, energy storage, air and water purification processes, and catalysis. In this review, main strategies for the realization of HCL polystyrene-based materials with advanced properties are reported, including a summary of the synthetic routes that are adopted for their realization and the chemical modification approaches that are used to impart them specific functionalities. Moreover, the most up to date results on the synthesis of HCL polystyrene-based nanocomposites that are realized by embedding these high surface area polymers with metal, metal oxide, and carbon-based nanofillers are discussed in detail, underlining the high potential applicability of these systems in different fields

Motion control in free-standing shape-memory actuators

In this work, free-standing shape-memory thermally triggered actuators are developed by laminating 'thiol-epoxy'-based glassy thermoset (GT) and stretched liquid-crystalline network (LCN) films. A sequential curing process was used to obtain GTs with tailored thermomechanical properties and network relaxation dynamics, and also to assemble the final actuator. The actuation extent, rate and time were studied by varying the GT and the heating rate in thermo-actuation with an experimental approach. The results demonstrate that it is possible to tailor the actuation rate and time by designing GT materials with a glass transition temperature close to that of the liquid-crystalline-to-isotropic phase transition of the LCN, thus making it possible to couple the two processes. Such coupling is also possible in rapid heating processes even when the glass transition temperature of the GT is clearly lower than the isotropization temperature of the LCN, depending on the network relaxation dynamics of the GT and the presence of thermal gradients within the actuators. Interestingly, varying the GT network relaxation dynamics does not affect the actuation extent. As predicted by the analytical model developed in our previous work, the modulus of the GT layer is mainly responsible for the actuation extent. Finally, to demonstrate the enhanced control of the actuation, specifically designed actuators were assembled in a three-dimensional actuating device able to make complex motions (including 'S-type' bending). This approach makes it possible to engineer advanced functional materials for application in self-adaptable structures and soft robotics.Postprint (author's final draft

Functional liquid crystalline epoxy networks and composites: from materials design to applications

Liquid crystalline epoxy networks (LCENs) are a class of materials that combine the useful benefits of both liquid crystals and epoxy networks exhibiting fascinating thermal, mechanical, and stimuli-responsive properties. They have emerged as a new platform for developing functional materials suitable for various applications, such as sensors, actuators, smart coatings and adhesives, tunable optical systems, and soft robotics. This article provides an overview of LCENs and their composites as functional materials, including their synthesis and characterisation, focusing on structure-processing–property relationships. We provide objective analyses on how materials engineers can use these relationships to develop LCENs with desired functionalities for targeted applications. Emerging areas, including advanced manufacturing and multi-functional design of LCENs are covered to show the overall progress in this field. We also survey the forward-looking status of LCEN research in designing novel materials for future technologies

Thermal and fire behavior of a bio-based epoxy/silica hybrid cured with methyl nadic anhydride

Thermosetting polymers have been widely used in many industrial applications as adhesives, coatings and laminated materials, among others. Recently, bisphenol A (BPA) has been banned as raw material for polymeric products, due to its harmful impact on human health. On the other hand, the use of aromatic amines as curing agents confers excellent thermal, mechanical and flame retardant properties to the final product, although they are toxic and subject to governmental restrictions. In this context, sugar-derived diepoxy monomers and anhydrides represent a sustainable greener alternative to BPA and aromatic amines. Herein, we report an “in-situ” sol–gel synthesis, using as precursors tetraethylorthosilicate (TEOS) and aminopropyl triethoxysilane (APTS) to obtain bio-based epoxy/silica composites; in a first step, the APTS was left to react with 2,5-bis[(oxyran-2-ylmethoxy)methyl]furan (BOMF) or diglycidyl ether of bisphenol A (DGEBA) monomers, and silica particles were generated in the epoxy in a second step; both systems were cured with methyl nadic anhydride (MNA). Morphological investigation of the composites through transmission electron microscopy (TEM) demonstrated that the hybrid strategy allows a very fine distribution of silica nanoparticles (at nanometric level) to be achieved within a hybrid network structure for both the diepoxy monomers. Concerning the fire behavior, as assessed in vertical flame spread tests, the use of anhydride curing agent prevented melt dripping phenomena and provided high char-forming character to the bio-based epoxy systems and their phenyl analog. In addition, forced combustion tests showed that the use of anhydride hardener instead of aliphatic polyamine results in a remarkable decrease of heat release rate. An overall decrease of the smoke parameters, which is highly desirable in a context of greater fire safety was observed in the case of BOMF/MNA system. The experimental results suggest that the eect of silica nanoparticles on fire behavior appears to be related to their dispersion degree

Bronchoscopic Intra-Pleural Instillation of Fibrin Glue and Autologous Blood to Manage Persistent Air Leaks after Lung Resection

Background: Persistent air leak is a common complication after lung resection causing prolonged length of stay and increased healthcare costs. Surgical intervention can be an option, but other more conservative approaches should be considered first. Here, we describe the use of flexible bronchoscopy to apply fibrin glue and autologous blood sequentially to the damaged lung. We named the technique "flexible thoracoscopy". Methods: Medical records from patients with persistent air leaks after lung resection were collected retrospectively. Depending on the type of aerostasis that was performed, two groups were created: flexible thoracoscopy and surgery (thoracotomy). Flexible thoracoscopy was introduced at our institution in 2013. We entered the pleural space with a bronchoscope following the same surgical pathway that was used for tube thoracostomy. Perioperative characteristics and outcomes were analyzed using R software (ver. 3.4.4). Results: From 1997 to 2021, a total of 23 patients required an intervention for persistent air leaks. Aerostasis was performed via flexible thoracoscopy in seventeen patients (69%) and via thoracotomy in six patients (31%). The median age was 70 years (22-82). Twenty patients were males (87%). There was no difference in age, sex distribution, BMI, comorbidities and FEV1%. An ASA score of 3 was more represented in the flexible thoracoscopy group; however, no evidence of a difference was found when compared to the thoracotomy group (p = 0.124). Length of in-hospital stay and chest tube duration was also similar between groups (p = 1 and p = 0.68, respectively). Conclusions: Aerostasis achieved either by flexible thoracoscopy or by thoracotomy showed similar results. We believe that flexible thoracoscopy could be a valid alternative to facilitate minimally invasive treatments for persistent air leaks. Further studies are needed to confirm these results