Polyureas Versatile Polymers for New Academic and Technological Applications

Polyureas (PURs) are a competitive polymer to their analogs, polyurethanes (PUs). Whereas PUs’ main functional group is carbamate (urethane), PURs contain urea. In this revision, a comprehensive overview of PUR properties, from synthesis to technical applications, is displayed. Preparative routes that can be used to obtain PURs using diisocianates or harmless reagents such as CO2 and NH3 are explained, and aterials, urea monomers and PURs are discussed; PUR copolymers are included in this discussion as well. Bulk to soft components of PUR, as well as porous materials and meso, micro or nanomaterials are evaluated. Topics of this paper include the general properties of aliphatic and aromatic PUR, followed by practical synthetic pathways, catalyst uses, aggregation, sol–gel formation and mechanical aspects.

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Specific features of the sol-gel formation and optical properties of nanostructured systems based on the oxides of tin and indium in the matrix of porous silicon

Glass Physics and Chemistry ◽

10.1134/s1087659615040112 ◽

2015 ◽

Vol 41 (4) ◽

pp. 417-420 ◽

Cited By ~ 1

Author(s):

A. S. Len’shin ◽

P. V. Seredin ◽

D. A. Minakov ◽

I. E. Kononova ◽

V. A. Moshnikov

Keyword(s):

Optical Properties ◽

Porous Silicon ◽

Sol Gel ◽

Gel Formation ◽

Nanostructured Systems ◽

The Matrix

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Specific-Ion Effects Directed Noble Metal Aerogels: Versatile Manipulation for Electrocatalysis and Beyond

10.26434/chemrxiv.7823702.v2 ◽

2019 ◽

Author(s):

RAN DU ◽

YUE HU ◽

René Hübner ◽

Jan-Ole Joswig ◽

Xuelin Fan ◽

...

Keyword(s):

Porous Materials ◽

Noble Metal ◽

Noble Metals ◽

Sol Gel ◽

Synthetic Methods ◽

Superior Performance ◽

Gelation Mechanism ◽

Practical Applications ◽

Specific Ion Effects ◽

Ion Effects

<div>Noble metal foams (NMFs) are a new class of functional porous materials featuring properties of both noble metals and monolithic porous materials, providing impressive prospects in catalysis, bio-sensing, plasmonic technologies, etc...Among reported synthetic methods to date, the sol-gel approach manifests overwhelming advantages for versatile synthesis of controlled nanostructured NMFs under mild condition. However, limited gelation methods and insufficient understanding of the underlying mechanism retards structure/composition manipulation of NMFs, hampering ondemand designing for practical applications. Herein highly tunable NMFs are fabricated at room temperature by activating specific-ion effects and regulating ion-nanoparticle interactions, affording various single/alloy NMFs with adjustable compositions (Au, Ag, Pd, Pt), ligament sizes (3.1~142.0 nm), and special morphologies. Their superior performance in programmable self-propulsion devices and electrocatalytic alcohol oxidation are demonstrated. This study provides not only a conceptually new route to fabricate and manipulate functional NMFs, but also an overall picture in understanding the gelation mechanism. It may pave the way for on-target designing versatile NMFs for various applications.</div>

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Preparation and Characteristics of an Environmentally Friendly Hyperbranched Flame-Retardant Polyurethane Hybrid Containing Nitrogen, Phosphorus, and Silicon

Polymers ◽

10.3390/polym11040720 ◽

2019 ◽

Vol 11 (4) ◽

pp. 720 ◽

Cited By ~ 4

Author(s):

Chen ◽

Chiang

Keyword(s):

Thermal Stability ◽

Flame Retardant ◽

Hybrid Material ◽

Functional Group ◽

Condensation Reaction ◽

Sol Gel ◽

Decomposition Temperature ◽

Limiting Oxygen Index ◽

Raman Analysis ◽

Ring Opening Reaction

The NCO functional group of 3-isocyanatoproplytriethoxysilane (IPTS) and the OH functional group of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phospha-phenantbrene-10-oxide (DOPO-BQ) were used to conduct an addition reaction. Following completion of the reaction, triglycidyl isocyanurate (TGIC) was introduced to conduct a ring-opening reaction. Subsequently, a sol–gel method was used to initiate a hydrolysis–condensation reaction on TGIC–IPTS–DOPO-BQ to form a hyperbranched nitrogen–phosphorous–silicon (HBNPSi) flame retardant. This flame retardant was incorporated into a polyurethane (PU) matrix to prepare a hybrid material. Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), limiting oxygen index (LOI), UV-VIS spectrophotometry, and Raman analysis were conducted to characterize the structure and analyze the transparency, thermal stability, flame retardancy, and residual char to understand the flame retardant mechanism of the prepared hybrid material. After the flame retardant was added, the maximum degradation rate decreased from −36 to −17 wt.%/min, the integral procedural decomposition temperature (IPDT) increased from 348 to 488 °C, and the char yield increased from 0.7 to 8.1 wt.%. The aforementioned results verified that the thermal stability of PU can be improved after adding HBNPSi. The LOI analysis indicated that the pristine PU was flammable because the LOI of pristine PU was only 19. When the content of added HBNPSi was 40%, the LOI value was 26; thus the PU hybrid became nonflammable.

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Quantitative Kinetic Analysis by High-Resolution 29Si NMR Spectroscopy of the Initial Stages in the Sol-Gel Formation of Silica Gel from Tetraethoxysilane

Chemistry of Materials ◽

10.1021/cm00058a008 ◽

1995 ◽

Vol 7 (10) ◽

pp. 1800-1806 ◽

Cited By ~ 33

Author(s):

Colin A. Fyfe ◽

Patricia P. Aroca

Keyword(s):

Nmr Spectroscopy ◽

High Resolution ◽

Kinetic Analysis ◽

Silica Gel ◽

Sol Gel ◽

29Si Nmr ◽

Gel Formation ◽

29Si Nmr Spectroscopy

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Specific features of the sol-gel formation and optical properties of 3d metal/porous silicon composites

Semiconductors ◽

10.1134/s1063782614040174 ◽

2014 ◽

Vol 48 (4) ◽

pp. 551-555 ◽

Cited By ~ 5

Author(s):

A. S. Lenshin ◽

P. V. Seredin ◽

D. A. Minakov ◽

V. M. Kashkarov ◽

B. L. Agapov ◽

...

Keyword(s):

Optical Properties ◽

Porous Silicon ◽

Sol Gel ◽

Gel Formation

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Sol–gel formation, Mössbauer studies, optical absorption and impedance characteristics of Ba0.5Sr0.5Zn0.2Fe0.8O3−ξ powder

Materials Chemistry and Physics ◽

10.1016/j.matchemphys.2012.06.013 ◽

2012 ◽

Vol 136 (1) ◽

pp. 28-35 ◽

Cited By ~ 7

Author(s):

Shivendra Kumar Jaiswal ◽

Jitendra Kumar

Keyword(s):

Optical Absorption ◽

Sol Gel ◽

Gel Formation ◽

Mössbauer Studies ◽

Impedance Characteristics

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Preparation of LaFeO3 particles by sol-gel technology

Journal of Materials Research ◽

10.1557/jmr.1998.0058 ◽

1998 ◽

Vol 13 (2) ◽

pp. 451-456 ◽

Cited By ~ 39

Author(s):

C. Vázquez-Vázquez ◽

P. Kögerler ◽

M. A. López-Quintela ◽

R. D. Sánchez ◽

J. Rivas

Keyword(s):

Particle Size ◽

Magnetic Properties ◽

Infrared Spectroscopy ◽

Sol Gel ◽

Diffraction Peak ◽

Gel Formation ◽

X Ray Diffraction ◽

X Ray ◽

Ferromagnetic Component ◽

Peak Broadening

The study of submicroscopic particles in already known systems has resulted in a renewed interest due to the large differences found in their properties when the particle size is reduced, and because of possible new technological applications. In this work we report the preparation of LaFeO3 particles by the sol-gel route, starting from a solution of the corresponding metallic nitrates and using urea as gelificant agent. Gels were decomposed at 200 °C and calcined 3 h at several temperatures, T, in the range 250–1000 °C. The samples were structurally characterized by x-ray diffraction (XRD) showing that the orthoferrite crystallizes at T as low as 315 °C. From the x-ray diffraction peak broadening, the particle size was determined. The size increases from 60 to 300 nm as the calcination T increases. Infrared spectroscopy was used to characterize gels and calcined samples. From these studies a mechanism for the gel formation is proposed. Study of the magnetic properties of LaFeO3 particles shows the presence of a ferromagnetic component which diminishes as the calcination temperature increases, vanishing at T = 1000 °C.

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