Improved Strength and Heat Distortion Temperature of Emi-Aromatic Polyamide 10T-co-1012 (PA10T/1012)/GO Composites via In Situ Polymerization

In this paper, an effective method for preparing poly (p-phenylene terephthalamide) -co- poly (dodecanedioyl) decylamine (PA10T/1012)/graphene oxide (GO) composites by pre-dispersion and one-step in situ polymerization was proposed for the first time. During the process of polycondensation, the condensation between the terminal amino groups of PA10T/1012 chains and the oxygen-containing functional groups of GO allowed nylon to be grafted onto graphene sheets. The effects of polymer grafting on the thermal and mechanical properties of (PA10T/1012)/GO composites were studied in detail. Due to the interaction between PA10T/1012 grafted graphene sheets and its matrix, GO is well dispersed in the PA10T/1012 matrix and physically entangled with it, forming a cross-linked network structure of polymer bridged graphene, thus obtaining enhanced tensile strength, tensile modulus and impact strength. More importantly, benefiting from the cross-linked network structure, the heat distortion temperature (HDT) of the composite is greatly increased from 77.3 °C to 144.2 °C. This in situ polycondensation method opens a new avenue to prepare polycondensate graphene-based composites with high strength and high heat distortion temperatures.

Recent Advances in Self-Assembly and Application of Para-Aramids

Poly(p-phenylene terephthalamide) (PPTA) is one kind of lyotropic liquid crystal polymer. Kevlar fibers performed from PPTA are widely used in many fields due to their superior mechanical properties resulting from their highly oriented macromolecular structure. However, the “infusible and insoluble” characteristic of PPTA gives rise to its poor processability, which limits its scope of application. The strong interactions and orientation characteristic of aromatic amide segments make PPTA attractive in the field of self-assembly. Chemical derivation has proved an effective way to modify the molecular structure of PPTA to improve its solubility and amphiphilicity, which resulted in different liquid crystal behaviors or supramolecular aggregates, but the modification of PPTA is usually complex and difficult. Alternatively, higher-order all-PPTA structures have also been realized through the controllable hierarchical self-assembly of PPTA from the polymerization process to the formation of macroscopic products. This review briefly summarizes the self-assembly methods of PPTA-based materials in recent years, and focuses on the polymerization-induced PPTA nanofibers which can be further fabricated into different macroscopic architectures when other self-assembly methods are combined. This monomer-started hierarchical self-assembly strategy evokes the feasible processing of PPTA, and enriches the diversity of product, which is expected to be expanded to other liquid crystal polymers.

Structures and properties of newly synthesized semi-aromatic polyamide thermoplastic elastomers

Novel semi-aromatic polyamide based thermoplastic elastomers containing both strong and weak H-bond units were fabricated via a facile “two-step” melt polycondensation method. The structures and properties of a series of TPAEs are discussed.

Multicomponent Reactions in Polymer Chemistry Utilizing Heavier Main Group Elements

Herein, a concise overview of the use of heavier main group elements in multicomponent reactions and their use in polymer chemistry is provided. Incorporating heavier elements into macromolecular structures via multicomponent reactions allows for the rapid development of materials with unique properties that are not readily achieved using carbon, nitrogen, and/or oxygen. Elements in Group 13, Group 14, Group 15, and Group 16 are specifically covered examining both the familiar and unfamiliar properties of these elements and how they are used in multicomponent chemistry. Furthermore, elements that both take part in the reaction mechanism and remain in the macromolecular structure upon completion are only briefly explored. Some of the state-of-the-art work going into developing these heavier element multicomponent reactions are highlighted and it is hoped to inspire other polymer chemists to explore other parts of the periodic table.

Economic Sulfur Conversion to Functional Polythioamides through Catalyst-Free Multicomponent Polymerizations of Sulfur, Acids, and Amines

Sulfur utilization is a global concern because of its abundant nature sources and the safety or environmental problems caused by its burning or oxidation during storage, while sulfur-containing polymers are popular materials in virtue of their fascinating properties such as metal coordination ability, high refractive indices, and semiconducting property. The synthesis of sulfur-containing polymers is challenging, especially directly from elemental sulfur. Herein, catalyst-free and scalable multicomponent polymerizations (MCPs) of all commercially available elemental sulfur, dicarboxylic acids, and diamines were reported to facilely construct 12 polythioamides with diverse and well-defined structures, high molecular weights (M_w's up to 86 200 g/mol), and excellent yields (up to 99%) from elemental sulfur. Besides commonly used aliphatic diamines, aromatic diamine monomers are also applicable to these multicomponent polymerizations, affording polythioamides with unique rigid structures and improved functionality as compared to those of the previously reported polythioamides. These polythioamides can be applied in gold recovery, which could extract a trace amount of Au³⁺ from practical acidic leaching solution of discarded electronic waste selectively, rapidly (1 min), sensitively (10 ppb), and efficiently (>99.99%) with high extraction capacity up to 0.60 g· Au³⁺/g to directly afford high-purity elemental gold after pyrolysis. The MCPs could make use of both abundantly existing sulfur waste and trace amounts of precious gold residue in electronic wastes, demonstrating their great potential in resource utilization.

Layer-by-Layer Self-Assembly Strategy for Surface Modification of Aramid Fibers to Enhance Interfacial Adhesion to Epoxy Resin

In this work, the layer-by-layer self-assembly technology was used to modify aramid fibers (AFs) to improve the interfacial adhesion to epoxy matrix. By virtue of the facile layer-by-layer self-assembly technique, poly(l-3,4-Dihydroxyphenylalanine) (l-PDOPA) was successfully coated on the surface of AFs, leading to the formation of AFs with controllable layers (nL-AF). Then, a hydroxyl functionalized silane coupling agent (KH550) was grafted on the surface of l-PDOPA coated AFs. The properties such as microstructure and surface morphology of AFs before and after modification were characterized by FTIR, XPS and FE-SEM. The results confirmed that l-PDOPA and KH550 were successfully introduced into the surface of AFs by electrostatic adsorption. The interfacial properties of AFs reinforced epoxy resin composites before and after coating were characterized by interfacial shear strength (IFSS), interlaminar shear strength (ILSS) and FE-SEM, and the results show that the interfacial adhesion properties of the modified fiber/epoxy resin composites were greatly improved.

Simple Synthesis of Hydroxyl and Ethylene Functionalized Aromatic Polyamides as Sizing Agents to Improve Adhesion Properties of Aramid Fiber/Vinyl Epoxy Composites

To improve interfacial adhesion between aramid fibers and vinyl epoxy resins, a series of hydroxyl and ethylene-functional aromatic polyamides ((ClPPTA)_m-R′) with different chain segments were successfully synthesized via a one-pot low-temperature polycondensation. The hydroxyl and ethylene-functional aromatic polyamides were characterized by Fourier transform infrared spectroscopy (FT-IR), solid-state ¹³C CP/MAS nuclear magnetic resonance spectroscopy (¹³C CP/MAS NMR), thermal gravimetric analysis (TGA), and wide-angle X-ray diffraction (WXRD). The contact angle of the hydroxyl and ethylene-functional aromatic polyamides films were measured. The hydroxyl and ethylene-functional aromatic polyamides were used as the sizing agents for aramid fiber/vinyl epoxy composites. The surface chemical composition and morphology of the unsized and sized fibers were identified using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The interfacial adhesion between aramid fibers and vinyl epoxy composites was investigated by the micro-debond tests. The results showed that the interfacial shear strength between the sized aramid fibers and vinyl epoxy composites was greatly improved.

Effects of a trans- or cis-cyclohexane unit on the thermal and rheological properties of semi-aromatic polyamides

Polyamides containing trans-formation cyclohexane unit was found to have better physical performance than that of sample with cis-formation such as mechanical, thermal and oxidation resistance properties etc.

Investigation of the synthesis and properties of isophorone and ether units based semi-aromatic polyamides

The resultant semi-aromatic polyamides showed excellent melt processability and mechanical, thermal and optical properties.

Preparation of poly(p-phenylene terephthalamide) in a microstructured chemical system

PPTA was prepared in a microstructured chemical system, and the apparent polycondensation kinetics was studied.