Multiphysics modelling of the mechanical properties in polymers obtained via photo-induced polymerization

Photopolymerization is an advanced technology to trigger free radical polymerization in a liquid monomer solution through light-induced curing, during which mechanical properties of the material are significantly transformed. Widely used in additive manufacturing, parts fabricated with this technique display precisions up to the nanoscale; however, the performance of final components is not only affected by the raw material but also by the specific setup employed during the printing process. In this paper, we develop a multiphysics model to predict the mechanical properties of the photo-cured components, by taking into account the process parameters involved in the considered additive manufacturing technology. In the approach proposed, the main chemical, physical, and mechanical aspects of photopolymerization are modelled and implemented in a finite element framework. Specifically, the kinetics of light diffusion from a moving source and chain formation in the liquid monomer is coupled to a statistical approach to describe the mechanical properties as a function of the degree of cure. Several parametric examples are provided, in order to quantify the effects of the printing settings on the spatial distribution of the final properties in the component. The proposed approach provides a tool to predict the mechanical features of additively manufactured parts, which designers can adopt to optimize the desired characteristics of the products.

Improved cationic dyeability of thermotropic liquid crystal polyarylate fabrics by ultraviolet irradiation-induced grafting of acrylic acid

As one of the most promising high-performance fibers, it is worthwhile to investigate the dyeing property of thermotropic liquid crystal polyarylate (TLCP) fibers. In this work, ultraviolet (UV) irradiation-induced grafting using the acrylic acid (AAc) method was employed to improve the cationic dyeability of the TLCP fabrics. The TLCP fabrics were firstly immersed in an AAc monomer solution for 24 h, followed with the UV radiation process for grafting polymerization. The results showed that the dyeing performance to C.I. Basic Red 46 of the modified TLCP fabrics was remarkably improved. Through several characterizations, it was found that the AAc-grafted TLCP fibers became more roughened with many pits on the fiber surface, while the crystalline structure of the TLCP fibers was hardly affected. More importantly, carboxyl groups have been successfully introduced onto the TLCP fiber surface, which is the main reason for the good dye uptake. Therefore, this paper provides a simple and efficient way for the improvement of the cationic dyeing property of TLCP fabrics.

Injectable Cryogels in Biomedicine

Cryogels are interconnected macroporous materials that are synthesized from a monomer solution at sub-zero temperatures. Cryogels, which are used in various applications in many research areas, are frequently used in biomedicine applications due to their excellent properties, such as biocompatibility, physical resistance and sensitivity. Cryogels can also be prepared in powder, column, bead, sphere, membrane, monolithic, and injectable forms. In this review, various examples of recent developments in biomedical applications of injectable cryogels, which are currently scarce in the literature, made from synthetic and natural polymers are discussed. In the present review, several biomedical applications of injectable cryogels, such as tissue engineering, drug delivery, therapeutic, therapy, cell transplantation, and immunotherapy, are emphasized. Moreover, it aims to provide a different perspective on the studies to be conducted on injectable cryogels, which are newly emerging trend.

Direct 2D-to-3D transformation of pen drawings

Pen drawing is a method that allows simple, inexpensive, and intuitive two-dimensional (2D) fabrication. To integrate such advantages of pen drawing in fabricating 3D objects, we developed a 3D fabrication technology that can directly transform pen-drawn 2D precursors into 3D geometries. 2D-to-3D transformation of pen drawings is facilitated by surface tension–driven capillary peeling and floating of dried ink film when the drawing is dipped into an aqueous monomer solution. Selective control of the floating and anchoring parts of a 2D precursor allowed the 2D drawing to transform into the designed 3D structure. The transformed 3D geometry can then be fixed by structural reinforcement using surface-initiated polymerization. By transforming simple pen-drawn 2D structures into complex 3D structures, our approach enables freestyle rapid prototyping via pen drawing, as well as mass production of 3D objects via roll-to-roll processing.

Preparation of Stainless Steel Mesh-Supported MnO2/Polypyrrole Nanocomposites as Binder-Free Electrode for Supercapacitor

Designing and preparation of excellent energy storage electrodes are of significance for supercapacitor. In this work, a self-supported electrode was successfully fabricated by electrodepositing MnO2 and polypyrrole (PPy) on stainless steel mesh (SSM) via amperometric measurements in different monomer solution. The electrode presented a specific capacitance of 239 F g[Formula: see text] at a current density of 1 A g[Formula: see text] and 86.7% capacitance retention after 10[Formula: see text]000 cycles. The in situ growth of MnO2 and PPy on SSM led to greater stability, higher conductivity and better robustness, which ensured the achievement of excellent electrochemical performance of the electrode accompanied with the synergetic effect between MnO2 and PPy to improve the electron transfer and take fully advantage of active materials.

Highly porous, fast responding acrylamide hydrogels through emulsion polymerization using coconut oil

Conventional acrylamide hydrogel exhibits a slow swelling rate which limits its potential for novel applications. It is a formidable challenge to increase the rate of swelling and if addressed successfully, this paves new paths for significant advanced applications. Fast responding polyacrylamide hydrogels with microporous structures and an interconnected network of capillary channels have been successfully synthesized by free radical emulsion-templated polymerization (a 2.5 m acrylamide monomer solution was crosslinked with 1% N,N-methylenebisacrylamide using 5% potassium persulfate as the initiator). Virgin coconut oil (70% v/v) was used as the pore forming agent, which was dispersed in the aqueous monomer solution by using 5% non-ionic surfactant (Tween 80®). Developed porous acrylamide hydrogel displayed approximately 600 wt% water absorptivity compared to the dry weight of the sample in 15 s at 30°C. Swelling ratio and scanning electron microscopy studies uncovered the characteristic microporous structure of the hydrogel. Pores of the hydrogel are interconnected to form capillary channels and thus they are responsible for the higher swelling rate of the hydrogel.

Development of a Simplified Radiation-Induced Emulsion Graft Polymerization Method and Its Application to the Fabrication of a Heavy Metal Adsorbent

A simplified radiation-induced emulsion graft polymerization (SREG) method is proposed. This method involves a convenient and easy degassing process of a monomer solution using a commercially available sealed glass jar. A loaded weight on the lid of the jar was used to control the jar’s internal pressure as the degassing of the monomer solution took place using a vacuum pump. The degassing method was highly reproducible, resulting from no bumping of the monomer solution. The initial grafting velocity was proportional to the absorbed doses of pre-irradiation between 5 and 20 kGy. This result indicates that dissolved oxygen was sufficiently eliminated from the monomer solution at such a level where the remaining oxygen had little effect on the grafting reaction at a dose of 5 kGy. The method was then applied to the fabrication of a heavy metal adsorbent that possessed a sufficient adsorption capacity of Co(II) ions. The SREG method is applicable to the fabrication of a wide variety of functional graft polymers because high-dose-rate gamma-ray radiation and expensive experimental equipment are not necessary.

Supermacroporous Composite Cryogels in Biomedical Applications

Supermacroporous gels, called cryogels, are unique scaffolds that can be prepared by polymerization of monomer solution under sub-zero temperatures. They are widely used in many applications and have significant potential biomaterials, especially for biomedical applications due to their inherent interconnected supermacroporous structures and easy formation of composite polymers in comparison to other porous polymer synthesis techniques. This review highlights the fundamentals of supermacroporous cryogels and composite cryogels, and then comprehensively summarizes recent studies in preparation, functionalization, and utilization with mechanical, biological and physicochemical features, according to the biomedical applications. Furthermore, conclusions and outlooks are discussed for the use of these promising and durable supermacroporous composite cryogels.

Comparison of Laboratory and Industrial Data on the Monomer Conversion during the Polymerisation of Isoprene

The results of a comparative analysis of the kinetic relationships governing the polymerisation of isoprene in the presence of titanium and neodymium catalysts, obtained under laboratory conditions and on industrial units of an operating high-tonnage synthetic rubber plant, are set out. It is shown that the conversion curve for the polymerisation of isoprene in the presence of a neodymium catalyst hardly depends on the conditions of monomer solution preparation (laboratory or industrial conditions). Under conditions of industrial production over a titanium catalyst, the monomer solution is polymerised at a lower rate by comparison with an isoprene solution prepared under laboratory conditions, which is possibly due to the presence of isoamylenes. The polymerisation of isoprene in a cascade of three polymerisation reactors in the presence of a neodymium catalyst is characterised by a lower rate by comparison with synthesis conducted by a batch method in laboratory dilatometers. The synthesis of polyisoprene in the presence of a titanium catalyst in a cascade of two high-volume polymerisation reactors proceeds at a greater rate by comparison with laboratory conditions. Comparison of the polymerisation rate in this case is qualitative in nature, as the polymerisation temperature under laboratory conditions amounted to 20°C, while under industrial conditions, with adiabatic heating up of the reaction mixture, the temperature increased from 0 to 52°C for the neodymium catalyst and from −5 to 55°C for the titanium catalyst.