Showing papers by "Igor Luzinov published in 2022"

Toward Mechanical Recycling of Polystyrene/Polypropylene Blends with Bottlebrush-Modified Graphene Oxide as a Compatibilizer.

Abstract: The compatibilization of immiscible polystyrene/polypropylene (PS/PP) blends with virgin graphene oxide (GO-V) and GO modified with a bottlebrush reactive copolymer layer (GO-P) is reported. This practically important blend was chosen since, currently, PS and PP are recycled to a very low degree. The amphiphilic bottlebrush copolymer synthesized by us contained hydrophobic and hydrophilic side chains and was attached to the GO nanosheets via epoxy functionality. The GO modification and the introduction of GO into the blend were conducted from water. Thus, the introduction of the compatibilizing nanomaterial can be conducted during the mechanical recycling washing stage in a real-world situation. The final blend was prepared via melt mixing using an extruder. We examined the influence of GO modification and the mixing order on the blends' morphology, rheology, and mechanical properties. Thermodynamic calculations predicted a higher interfacial activity of GO nanosheets in PS/PP/GO-P blends than that in PS/PP/GO-V blends. The morphological and rheological study assessed this prediction. It was demonstrated that the bottlebrush-modified GO-P sheets were readily driven to the PS/PP interphase. The mechanical measurements showed enhanced mechanical properties for PS/PP/GO-P blends, especially for those in which GO was first premixed with PS.

Mesoscale Modeling of Agglomeration of Molecular Bottlebrushes: Focus on Conformations and Clustering Criteria

Abstract: Using dissipative particle dynamics, we characterize dynamics of aggregation of molecular bottlebrushes in solvents of various qualities by tracking the number of clusters, the size of the largest cluster, and an average aggregation number. We focus on a low volume fraction of bottlebrushes in a range of solvents and probe three different cutoff criteria to identify bottlebrushes belonging to the same cluster. We demonstrate that the cutoff criteria which depend on both the coordination number and the length of the side chain allows one to correlate the agglomeration status with the structural characteristics of bottlebrushes in solvents of various qualities. We characterize conformational changes of the bottlebrush within the agglomerates with respect to those of an isolated bottlebrush in the same solvents. The characterization of bottlebrush conformations within the agglomerates is an important step in understanding the relationship between the bottlebrush architecture and material properties. An analysis of three distinct cutoff criteria to identify bottlebrushes belonging to the same cluster introduces a framework to identify both short-lived transient and long-lived agglomerates; the same approach could be further extended to characterize agglomerates of various macromolecules with complex architectures beyond the specific bottlebrush architecture considered herein.

Poly(3-hexylthiophene)-Based Organic Thin-Film Transistors with Virgin Graphene Oxide as an Interfacial Layer

Abstract: We fabricated and characterized poly(3-hexylthiophene-2, 5-diyl) (P3HT)-based Organic thin-film transistors (OTFTs) containing an interfacial layer made from virgin Graphene Oxide (GO). Previously chemically modified GO and reduced GO (RGO) were used to modify OTFT interfaces. However, to our knowledge, there are no published reports where virgin GO was employed for this purpose. For the sake of comparison, OTFTs without modification were also manufactured. The structure of the devices was based on the Bottom Gate Bottom Contact (BGBC) OTFT. We show that the presence of the GO monolayer on the surface of the OTFT’s SiO2 dielectric and Au electrode surface noticeably improves their performance. Namely, the drain current and the field-effect mobility of OTFTs are considerably increased by modifying the interfaces with the virgin GO deposition. It is suggested that the observed enhancement is connected to a decrease in the contact resistance of GO-covered Au electrodes and the particular structure of the P3HT layer on the dielectric surface. Namely, we found a specific morphology of the organic semiconductor P3HT layer, where larger interconnecting polymer grains are formed on the surface of the GO-modified SiO2. It is proposed that this specific morphology is formed due to the increased mobility of the P3HT segments near the solid boundary, which was confirmed via Differential Scanning Calorimetry measurements.

Toward the Replacement of Long-Chain Perfluoroalkyl Compounds: Perfluoropolyether-Based Low Surface Energy Grafted Nanocoatings

Abstract: We describe a straightforward approach to fabricating perfluoropolyether (PFPE)-based nanocoatings, significantly decreasing the spreading of oil and water on coated surfaces. In the fabrication, polyglycidyl methacrylate (PGMA) is used as an anchoring layer deposited on the silicon surface before PFPE attachment. Perfluoropolyether-based polyester acid (PFPE-COOH) is then grafted to the PGMA surface to reduce its surface energy and, consequently, wettability. The grafted surface demonstrates a hexadecane contact angle of 40–46° and a water contact angle of 80–98°. The surface’s wettability strongly depends on the grafted layer thickness, where grafting of the thicker PFPE layers results in lower oil and water wettability. We expect that the employment of PFPE-based grafted nanocoatings will eliminate the health and environmental concerns of long perfluoroalkyls, which are typically used to obtain surfaces with decreased spreading of oil and water.

The Effect of a Copolymer Interfacial Layer on the Performance of Organic Thin-Film Transistors

Abstract: The effects of adding a copolymer interfacial layer on the performance of Poly (3-hexylthiophene-2, 5-diyl) (P3HT) based organic thin-film transistors (OTFT) were investigated. Poly (oligo (ethylene glycol) methyl ether methacrylate- glycidyl methacrylate- lauryl methacrylate), which is referred to as POGL, was used as an interfacial layer between P3HT and the dielectric. OTFTs with and without a POGL interfacial layer were fabricated. The field-effect mobility and the threshold voltage were extracted for all the devices. The OTFTs with a POGL interfacial layer were observed to have a smaller threshold voltage than the OTFTs without an interfacial layer, which makes the POGL devices attractive for low power applications. The POGL OTFTs were also observed to have much more ideal drain current saturation characteristics with very small I-V curve slope. This is explained by the deep trap states on the POGL surface and the reduction of the contact resistance at the electrode/organic semiconductor interface. However, the POGL OTFTs were observed to have a smaller drain current and a slightly smaller mobility than the non-POGL OTFTs. This is explained by the surface roughness of the POGL, which affects the charge transport in the channel of the device.

(Digital Presentation) The Effect of a Copolymer Interfacial Layer on the Performance of Organic Thin-Film Transistors

Abstract: The effects of adding a copolymer interfacial layer on the performance of Poly (3-hexylthiophene-2, 5-diyl) (P3HT) based organic thin film transistors (OTFT) were investigated. Poly (oligo (ethylene glycol) methyl ether methacrylate- glycidyl methacrylate- lauryl methacrylate), which is referred to as POGL, was used as an interfacial layer between P3HT and the dielectric. OTFTs with and without a POGL interfacial layer were fabricated. The devices were based on the bottom gate bottom contact structure. Current–Voltage (I-V) measurements were performed to characterize the performance of the OTFTs, and atomic force microscopy (AFM) measurements were used to analyze the morphology of the POGL and P3HT surfaces. The field effect mobility and the threshold voltage were extracted for all the devices. The OTFTs with a POGL interfacial layer were observed to have a smaller threshold voltage than the OTFTs without an interfacial layer, which makes the POGL devices attractive for low power applications. The POGL OTFTs were also observed to have much more ideal drain current saturation characteristics with very small I-V curve slope. This is explained by the deep trap states on the POGL surface. However, the POGL OTFTs were observed to have a smaller drain current and mobility than the non-POGL OTFTs. This is explained by the surface roughness of the POGL, which affects the charge transport in the channel of the device. The morphology of the P3HT on POGL surface also showed a higher density of voids and non-uniform coverage than P3HT on the SiO2 surface, contributing to the smaller drain current and mobility of the POGL devices.