https://cyberleninka.org/article/n/1018032.pdf

Polymer nanotechnology: Nanocomposites

Layered double hydroxides (LDHs) have been investigated for many years as host materials for a range of anion exchange intercalation reactions. In this role they have been used extensively as ion-exchange materials, catalysts, sorbents and halogen absorbers. More recently, there have been a tremendous number of new developments using these materials to store and deliver biologically active materials in vivo. Significant advances have been made recently on the characterisation of these materials, including structural studies and on the mechanism of intercalation using in situ techniques.

Intercalation chemistry of layered double hydroxides: recent developments and applications

The use of layered inorganic solids as host materials for the creation of inorganic–organic host-guest supramolecular structures is of increasing interest. In this review we outline the preparation, characterization and uses of layered double hydroxides (LDHs) containing organic guests. LDHs consist of stacks of positively charged mixed metal hydroxide layers that require the presence of interlayer anions to maintain overall charge neutrality. A range of organic guests may be incorporated, including aliphatic and aromatic carboxylates, sulfonates and phosphonates as well as porphyrin and phthalocyanine derivatives. Potential applications of organo-LDHs in the areas of catalysis, sorption, photochemistry and electrochemistry are outlined. Overall, it is demonstrated that with LDHs it is possible to create, in a systematic manner, novel inorganic–organic supramolecular structures.

Synthesis, characterization and applications of layered double hydroxides containing organic guests

The present paper describes the synthesis and characterization of nanocomposite materials built from the assembly of organic polymers and two-dimensional host materials, particularly reviewing those composed of layered double hydroxide (LDH) inorganic frameworks. When the meaning commonly adopted for nanocomposites is narrowed, the system is constituted of sheets lying on top of each other in which covalent forces maintain the chemical integrity and define an interlamellar gap filled up with the polymer guest. The situation is different from an inorganic filler dispersed into a polymeric matrix. The incorporation of polymer between the galleries proceeds via different pathways such as coprecipitation, exchange, in situ polymerization, surfactant-mediated incorporation, hydrothermal treatment, reconstruction, or restacking. The latter method, recently effective via the exfoliation of the LDH layers, appears to be more favorable, in terms of crystallinity, to capture monomer entities than the whole polymer....

Polymer Interleaved Layered Double Hydroxide: A New Emerging Class of Nanocomposites

The review renders a short background on the research work carried out on epoxy clay nanocomposites Clays are one of the ideal nano reinforcements for polymers because of their high intercalation chemistry and aspect ratio Epoxy clay nanocomposites are finding vast applications in various industries like aerospace, defense, automobile, etc The physical and chemical properties of the epoxy systems are influenced by the processing techniques, clay modifier and curing agents used for the preparation of nanocomposites The clay morphology (intercalation/exfoliation) of the nanocomposites is also depended on the above parameters So the emphasis of the present work is to highlight these parameters on morphology and the final mechanical, thermal and barrier properties of the nanocomposites The proposed applications of the epoxy clay nanocomposites are also discussed

Epoxy clay nanocomposites ― processing, properties and applications: A review

Organically modified layered silicates (OLS) with high thermal stability are critical for synthesis and processing of polymer layered silicate nanocomposites (PLSN). In the current study, the non-oxidative thermal degradation chemistry of alkyl and aryl quaternary phosphonium-modified montmorillonites (P-MMT) was examined using TGA combined with pyrolysis/GC-MS. The morphology evolution at elevated temperature was investigated using in-situ high-temperature X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The onset decomposition temperature via TGA of these P-MMTs ranged from 190 to 230 °C. The initial degradation of the alkyl P-MMTs follows potentially two reaction pathways - ‚-elimination [E‚] and nucleophilic displacement at phosphorus [SN(P)] reflecting the multiple environments of the surfactant in the silicate. Aryl P-MMT decomposition proceeds via either a reductive elimination through a five-coordinate intermediate or radical generation through homologous cleavage of the P-phenyl bond. Overall, the interlayer environment of the montmorillonite has a more severe effect on stability of the phosphonium surfactant than previously reported for ammonium-modified montmorillonite (N-MMT). Nonetheless, the overall thermal stability of P-MMT is higher than that of N-MMT. These observations indicate that, in addition to their conventional purpose as stabilizers, phosphonium salts offer unique opportunities for melting processing polymer layered silicate nanocomposites.

Thermal Stability of Quaternary Phosphonium Modified Montmorillonites

Two distinct V(9)O(23) building blocks having different vanadium coordination environments are intergrown in the unusual layered vanadate [N(CH(3))(4)](5)V(18)O(46) (see picture). Lattice strain is relieved by alternation of the vanadate strips formed from the blocks in both directions (akin to a three-dimensional tire tread). The formation of this lattice has implications for the assembly mechanism of this compound and related materials in hydrothermal synthesis.

An Inorganic Tire-Tread Lattice: Hydrothermal Synthesis of the Layered Vanadate [N(CH3)4]5V18O46 with a Supercell Structure

The first hydrothermal synthesis and crystal structure of a novel organically templated layered vanadium oxide is described; the structural units of (C6H14N2)V6O14 are comprised of a unique arrangement of VO5 square pyramids and VO4 tetrahedra that are interconnected to form highly puckered sheets that are separated by diazabicyclooctane cations which act as the template in the synthesis.

Hydrothermal Synthesis and Crystal Structure of a Novel Layered Vanadate with 1,4-Diazabicyclo[2.2.2]octane as the Structure-Directing Agent: (C6H14N2)V6O14·H2O

Disclosed are novel compositions that include at least one type of layered silicate as well as methods for making same. In one aspect, the invention features silicate compositions that include at least one type of layered silicate and at least one type of organophilic agent associated with the silicate. Also provided are nanocomposites that include the silicate composition and at least one suitable polymer material. The invention has a wide spectrum of useful applications including providing manufactured articles with exceptional performance characteristics.

Bryan E. Koene

Papers

Thermal Stability of Quaternary Phosphonium Modified Montmorillonites

An Inorganic Tire-Tread Lattice: Hydrothermal Synthesis of the Layered Vanadate [N(CH3)4]5V18O46 with a Supercell Structure

Hydrothermal Synthesis and Crystal Structure of a Novel Layered Vanadate with 1,4-Diazabicyclo[2.2.2]octane as the Structure-Directing Agent: (C6H14N2)V6O14·H2O

High performance nanocomposites

Preparation, reactivity, and x-ray structure of a cationic alkoxyzirconocene complex