دو ماهنامه علوم و تکنولوژی پلیمر
سال سی و ششم شماره 2 (پیاپی 184، خرداد و تیر 1402)

In recent years, the performance of perovskite solar cells (PSCs) has made a significant growth of about 25.5%. Nonetheless, the long-term stability of these cells for industrial production is still a major concern. One of the important reasons for the instability and degradation of the perovskite layer is its sensitivity toward moisture, oxygen, lack of resistance to ultraviolet light, electric fields, and temperature. In this context, hole-transporting materials (HTMs) play a key role in the construction of a stable inverted perovskite solar cell, including regulating the growth and crystallization of the perovskite and creating a water-repellent surface with a suitable structure. Naturally, the function of a hole-transporting layer depends on the type of perovskite solar cell configuration, and it is discussed in detail in the relevant section. In recent decades, researchers have focused on developing stable HTMs based on additive and non-additive semi-conducting polymers. Polymers have unique properties such as adjustable molecular weight, easier mobility of the hole compared to organic compounds, and suitable conductivity under additive-free conditions for 3D printing applications at an industrial scale. In addition, the cost-effectiveness of synthesis steps and potential interlayer displacement during the manufacturing process has made attraction and innovations in this area. Therefore, this article evaluates and analyzes the performance and mechanism of hole-transporting layers based on p-type semi-conducting polymers and the effect of various component structures of polymer systems on the inverse perovskite solar cell system. Polymers such as, pol(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), and (poly(3-hexylthiophene) (P3HT) have received most of the research and experimentation, with PTAA being the most desirable and efficient option, reaching over 25% efficiency.

Hypothesis: 

Some adducts were prepared from three kinds of DGEBA-based epoxy resins, phthalic anhydride and an alkanol amine accelerator, as a latent accelerator for one-pot epoxy/dicy systems. These adducts come with two kinds of accelerators: DMP-30 A, which is lab-grade and Ax-10, which is industrial-grade, as well as DGEBA based epoxy resins Epikote 828, Epiran 06 and ML 504. The adduct made of Epikote 828 and DMP-30 A was considered as a reference. It seems that it might be possible to prepare a new efficient latent accelerator with change of epoxy resin and accelerator.

For this purpose, four different adducts with resins and accelerators and four different epoxy/dicy mixtures with four adduct types and AX-10 accelerator and one with no adduct as a reference were prepared. Measuring the melting point, viscosity build-up versus time, gelation time, non-isothermal differential scanning calorimetry (DSC) and glass transition temperature characterization and also lap shear, interlaminar shear strength, transvers tensile and scanning electron microscope (SEM) were used to study the latent properties of the prepared adducts in the epoxy/dicy system and find its effect on mechanical properties of the final composites and all were compared with references.

Melting point of all adducts is above room temperature, so they are solid at room temperature. The results show that the adducts containing the industrial accelerator in one-pot epoxy/dicy system has lower gel time at high temperature, higher viscosity changes at ambient temperature and pot life and has made no significant change in cure temperature. The mechanical properties of the composite made with an adduct consisting of ML 504 resin are accompanied by a decrease in the related values. In general, the adduct made with Epiran 06 or Epikote 828 resin and industrial accelerator is an efficient and new latent accelerator and is suitable for preparing one-pot epoxy/dicy systems.

Hypothesis: 

The effect of incorporation of carbon black nanoparticles (CB) and nano-precipitated calcium carbonate (NPCC) on wear behavior, thermal behavior and morphology in polyacetal (POM)-based nanocomposite gears has been studied. Polyacetal is one of the widely used engineering materials for manufacturing the gears. Nevertheless, heat resistance and relatively low crack impact strength and sensitivity to UV are the major disadvantage of POM. Adding carbon black nanoparticles into the polyacetal can simultaneously increase the tensile strength and toughness and increase the UV resistance of the polyacetal. In addition, the presence of NPCC in the POM/CB can lead to improvements in CB dispersibility, increase of wear and thermal resistance.

POM/CB/NPCC nanocomposite gears containing 0.42% (by wt) carbon black and different fractions (1.5%, 3% and 4.5% all by wts) of NPCC were produced by utilizing a twin-screw extruder and injection molding machine. Morphology and nanostructure were investigated by applying scanning electron microscopy. The gear performance of nanocomposites was examined by applying a gear test rig. Gear tests were performed in the mode constant loading. The temperature and wear of the gears were evaluated in the gear tests. 

The simultaneous addition of both types of nanoparticles to polyacetal led to a reduction in the amount of wear by 58% compared to pure polyacetal. The temperature of the gear surface, in the same number of revolutions, was reduced using CB and NPCC nanoparticles. The decrease in the temperature of the nanocomposite tooth surface compared to pure POM was attributed to the increase in storage modulus and improvement in elastic behavior, decrease in damping ratio, as well as decrease in friction coefficient and increase in heat transfer in presence of nanoparticles. The use of 4.5% (by wt) of NPCC nanoparticles caused cracks and expansion of wear and material flow in the gear pitch zone.

Hypothesis:

 Due to the alternating hydroxyl and secondary amine groups, the polymer poly(1-(2-((3-amino-2-hydroxypropyl)amino)ethyl)-1'-ethyl-[4,4'-bipyridine]-1,1'-diium) (poly(AHAEBD)), is highly prone to complex formation. In this case, iron (III) was selected for complexation with poly(AHAEBD) due to its effective role in metabolic activities in the body then, anticancer effects of the synthesized compounds were evaluated on human breast cancer cells (MCF-7). 

1,1'-Bis(2-aminoethyl)-[4,4'-bipyridine]-1,1'-diium (BABD) was prepared from the reaction of 4,4'-bipyridine and 2-aminoethyl. The polymer, (poly(AHAEBD)), was synthesized from the reaction of BABD and epichlorohydrin, and then complexed with iron (III) to prepare ([Fe(poly(AHAEBD)2].Na3). The structure of the synthesized compounds was confirmed using Fourier transfer infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR) spectroscopy, field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), and gel permeation chromatography (GPC). The effects of [Fe(poly(AHAEBD)2].Na3, poly(AHAEBD), and cisplatin as a reference were evaluated on MCF-7 cell line using the MTT assay. 

The IC50 values for the polymer complex [Fe(poly(AHAEBD)2].Na3 (0.53 µg/mL), cisplatin (2.68 µg/mL), and poly(AHAEBD) (1.14 µg/mL) were obtained, indicating the superior performance of this polymer complex in inhibiting cancer cell growth compared to cisplatin as well as displaying the effect of complex formation with iron in increase the cytotoxicity compared to poly(AHAEBD). The impact of the synthesized polymer on the MCF-7 cancer cell line, on one hand, as well as the effect of increased iron levels in stopping the growth of cancer cells, and on the other hand, it has resulted in the effective performance of this complex polymer in stopping the growth of cancer cells in in vitro tests. Based on the results obtained, this polymer complex can be considered as a potential candidate for further investigation as an anticancer drug.

Hypothesis: 

In elastomeric composites, interfacial phenomena such as the effect of reinforcing filler on molecular dynamics of the rubber chain in the interphase and the way of rubber-filler interaction are the source of strain energy change or viscoelastic loss of the composite in highly filled rubber compound. To obtain a preliminary approximation of how the strain energy is influenced by interfacial phenomena, including stiffness, loss and the quality of this region, in this research, the finite element microstructural model was created in two-dimensional and three-dimensional mode and the effective characteristic changes in mechanical properties were studied. The effect of the change in stiffness of the interphase and the change in viscoelastic nature, the amount of contact between the rubber-filler in completely bonded and frictional sliding states were modeled.

The solution styrene butadiene rubber composites reinforced with silica were prepared by melt mixing. For this purpose, rubber was mixed with silica and silane coupling agent in an internal mixer. Then the masterbatch was mixed with the curing system on a two-roll mill and finally the sample was cured under pressure at 160°C.

In agreement with the modeling results, the composite tensile test showed that the most important controlling parameter is the type of rubber-filler connection in the interphase. The simulation results showed that considering the interphase region with frictional sliding greatly reduces the stress transfer from the matrix to the particle. But in the case of the completely bonded interphase region, due to the complete transfer of stress from the particle to the matrix, the mechanical properties showed a significant deviation compared to the experimental results. Also, the 3D models provided better predictions than the 2D ones.

Hypothesis: 

Chemical cross-linked shape memory polyurethanes (CSMPUs) can have various applications in different fields such as medicine, where mechanical behavior and shape memory are improved in these samples compared to linear shape memory polyurethanes. Shape memory polyurethanes consist of at least two different phases. The first phase, which is in the form of a net point, is responsible for maintaining the permanent shape of the shape memory polyurethane. In contrast, the second phase, also known as shape memory switches, temporarily fixes the temporary shape of the polyurethane by crystallinity. The aim of this research is the synthesis of linear and star polycaprolactones (PCLs) in the first step and the synthesis of CSMPUs using linear and star PCLs in the second step, as well as the investigation and comparison of hydrogen-bonding indices through -C=O groups and -NH CSMPU samples that were synthesized using glycerol as the initiator of the soft segment or the chain extender of the hard segment.

Linear and star polycaprolactones (PCLs) were synthesized using ring-opening polymerization (ROP) of caprolactone, and shape memory polyurethanes with chemical cross-linking (CSMPU) were synthesized using a two-step pre-polymerization method. By changing the molar ratios of the functional groups, the weight percentage of the hard segment in polyurethane samples was kept constant at 10%.

The hydrogen-bond index is decreased with the introduction of glycerol as a chain extender. Also, the degree of crystallinity in CSMPU samples is decreased compared to those of pure PCLs. With the increase of chemical cross-linking the crystallinity of CSMPU samples is decreased. In addition, in the studies of mechanical behavior no significant difference was observed in the presence of glycerol in the soft segment or the hard segment.