Development of PAMAM dendrimer-modified magnetic polyoxometalate: A novel platform to reinforce mechanical and thermal properties of diglycidyl ether of bisphenol A/isophorone diamine hardener epoxy

The present study explores the mechanical and thermal properties of DGEBA/IPD epoxy reinforced with dendrimer-functionalized magnetitepolyoxometalate nanoparticles. Magnetic iron oxide nanoparticles (MNP’s) were stabilized and functionalized by the poly (amido-amine) dendrimer via encapsulation within dendrimer; afterwards, H9 [α-P2V3W15O62] polyoxometalate (POM) was modified with dendrimer-functionalized magnetic iron oxide nanoparticles (DMNP’s). The polyoxometalate can be complexed with DMNP’s via protonation of dendrimer amino groups. In the next step, dendrimer-functionalized magnetitepolyoxometalate nanoparticles (DMNP’s-POM) were loaded into diglycidyl ether of bisphenol A (DGEBA) epoxy resin. The DMNP’s-POM nanoparticles can initiate polymerizations of epoxy resin with isophorone diamine hardener (IPD); on the other hand, the terminal amino groups of the dendrimer in the DMNP’s-POM nanoparticles allow them to be covalently linked to the polymer matrix alongside the main amine hardener. The resulting epoxy/magnetitepolyoxometalate nanocomposites (DMNP’s-POM@EN 5%) are thoroughly characterized by FT-IR, FE-SEM, and XRD analysis. Probing thermal behaviors of epoxy/magnetitepolyoxometalate nanocomposites by TGA reveals that the resulting composites are degraded thermally through a simple one-step process with an initial degradation close to 340°C, and show significant stability toward heat. Dynamic Mechanical Thermal Analysis indicates that no considerable agglomerate is formed during the synthesis process, and the incorporated nanoparticles somewhat limit the segmental motions of the epoxy macromolecular chains.

Effect of dendrimer-functionalized magnetic iron oxide nanoparticles on improving thermal and mechanical properties of DGEBA/IPD epoxy networks

In this work, the effects of dendrimer-functionalized magnetic iron oxide nanoparticles (Fe3O4@D-NH2) on improving thermal and mechanical properties in epoxy networks (ENs) are investigated. Magnetic iron oxide nanoparticles are prepared by coprecipitation of iron (II) chloride tetrahydrate with iron (III) chloride hexahydrate. Poly(amido-amine) dendrimer is synthesized by Michael addition reaction from diethylenetriamine with methyl acrylate. The fabricated dendrimer has been used to stabilize and functionalize magnetic nanoparticles. Then, magnetic iron oxide nanoparticles are encapsulated within the dendrimer and subsequently loaded into diglycidyl ether of bisphenol A (DGEBA) epoxy resin in two different contents, that is, 5 and 10 wt%. The amine groups of dendrimer-functionalized magnetic iron oxide nanoparticles allow them to be covalently linked to the polymer matrix alongside the main amine hardener. The resulting epoxy/magnetic iron oxide nanocomposites are thoroughly characterized by X-ray diffraction analysis, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. Probing the thermal behaviors of the epoxy/magnetic iron oxide nanocomposites by thermogravimetric analysis indicated that the temperature of 10% decomposition and the temperatures of the maximum decomposition rate values of Fe3O4@D-NH2@EN series increased up to 20 and 10°C, respectively. Dynamic mechanical thermal analysis also indicated that the organo-magnetic iron oxide nanoparticles can lead to an excellent interaction between the nanoparticles and the resulting DGEBA/isophorone diamine ENs.

Preparation and Properties of Polyamide Dendrons-Poly(4-Vinylpyridine) Complexes via Multiple Hydrogen Bonding

The preparation and properties of the multiple hydrogen-bonded complexes between polyamide dendrons and poly(4-vinylpyridine) (P4VP) are described. Polyamide dendrons with or without carboxyl groups were prepared as components for the complex with P4VP. A hydrogen-bonded G1-GA (polyamide dendron having five carboxyl groups)/P4VP 1/5 (molar ratio) complex was prepared by mixing G1-GA with P4VP in methanol, followed by removing the solvent. The formation of the hydrogen bond was confirmed by IR measurements. A glass transition temperature ( Tg) of the complex was observed at 179′C by DSC measurement, whereas the melting point of G1-GA (156′C) and Tg of P4VP (144′C) disappeared. The Tg of G1-GA/P4VP complexes was dependent on the molar ratio ([Acceptor]/[Donor]). The maximum Tg at 184′C was observed in the acceptor-rich region. 1H NMR spin-lattice relaxation time ( T1) and diffusion coefficient ( D) were measured to evaluate the mobility of G1-GA or P4VP in solution. Both T1 and D values suggest that the mobility of the dendron and P4VP in the complex is restricted by the formation of multiple hydrogen bondings in solution.

Synthesis and Properties of Carboxylated Dendritic Polyamide-b-Poly(4-vinylpyridine) Block Copolymers Capable of Multiple Hydrogen Bonding

A dendritic aromatic polyamide having carboxyl groups on the periphery and a benzyl chloride group at the core (Cl-G1-4COOH) was prepared as an initiator for atom transfer radical polymerization (ATRP). The ATRP of 4-vinylpyridine initiated by Cl-G1-4COOH was carried out in the presence of tris[2-(dimethylamino)ethyl]amine (Me6 TREN) and CuCl to form tadpole-shaped dendritic-linear copolymers (P4VP-G1-4COOH). The structure of P4VP-G1-4COOH was confirmed by nuclear magnetic resonance (NMR) and infrared measurements. The thermal and solution properties of P4VP-G1-4COOH are influenced by the multiple hydrogen bonding between the carboxyl groups on the periphery and vinylpyridine segments. A glass transition temperature value that is higher than that of Cl-G1-4COOH could be due to the contribution of the multiple hydrogen bonding. The decreased solubility in methanol and chloroform suggests the presence of the multiple hydrogen bonding. The solubility of each component also affected the association of P4VP-G1-4COOH in solution. A structural model for the molecular interaction of P4VP-G1-4COOH in methanol, chloroform and N, N-dimethylformamide based on the hydrodynamic radii and NMR measurements is proposed..