Comparison of the mechanical properties of polymer blend and main-chain conjugated copolymer films with donor–acceptor heterojunctions

P(BDBT-co-NDI2T) exhibited a strong absorption band, which overlapped with the emission spectrum of an LED lamp and it exhibited a high power conversion efficiency of 12.70% under the LED lamp (@500 lux).

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Internal constraints and arrested relaxation in main-chain nematic elastomers

Nature Communications ◽

10.1038/s41467-021-21036-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Takuya Ohzono ◽

Kaoru Katoh ◽

Hiroyuki Minamikawa ◽

Mohand O. Saed ◽

Eugene M. Terentjev

Keyword(s):

Mechanical Properties ◽

Main Chain ◽

Polymer Networks ◽

Nematic Order ◽

Nematic Elastomers ◽

Nematic Director ◽

Highly Nonlinear ◽

Nonlinear Mechanical ◽

Liquid Crystal Elastomers ◽

Memory Applications

AbstractNematic liquid crystal elastomers (N-LCE) exhibit intriguing mechanical properties, such as reversible actuation and soft elasticity, which manifests as a wide plateau of low nearly-constant stress upon stretching. N-LCE also have a characteristically slow stress relaxation, which sometimes prevents their shape recovery. To understand how the inherent nematic order retards and arrests the equilibration, here we examine hysteretic stress-strain characteristics in a series of specifically designed main-chain N-LCE, investigating both macroscopic mechanical properties and the microscopic nematic director distribution under applied strains. The hysteretic features are attributed to the dynamics of thermodynamically unfavoured hairpins, the sharp folds on anisotropic polymer strands, the creation and transition of which are restricted by the nematic order. These findings provide a new avenue for tuning the hysteretic nature of N-LCE at both macro- and microscopic levels via different designs of polymer networks, toward materials with highly nonlinear mechanical properties and shape-memory applications.

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Halloysite Nanotubes and Silane-Treated Alumina Trihydrate Hybrid Flame Retardant System for High-Performance Cable Insulation

Polymers ◽

10.3390/polym13132134 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2134

Author(s):

Sandra Paszkiewicz ◽

Izabela Irska ◽

Iman Taraghi ◽

Elżbieta Piesowicz ◽

Jakub Sieminski ◽

...

Keyword(s):

Mechanical Properties ◽

Polymer Blend ◽

Hybrid System ◽

Reference Sample ◽

Melt Flow Index ◽

Halloysite Nanotubes ◽

Flow Index ◽

Scanning Calorimetry ◽

Limiting Oxygen Index ◽

Alumina Trihydrate

The effect of the presence of halloysite nanotubes (HNTs) and silane-treated alumina trihydrate (ATH-sil) nanofillers on the mechanical, thermal, and flame retardancy properties of ethylene-vinyl acetate (EVA) copolymer/low-density polyethylene (LDPE) blends was investigated. Different weight percentages of HNT and ATH-sil nanoparticles, as well as the hybrid system of those nanofillers, were melt mixed with the polymer blend (reference sample) using a twin-screw extruder. The morphology of the nanoparticles and polymer compositions was studied using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The mechanical properties, hardness, water absorption, and melt flow index (MFI) of the compositions were assessed. The tensile strength increases as a function of the amount of HNT nanofiller; however, the elongation at break decreases. In the case of the hybrid system of nanofillers, the compositions showed superior mechanical properties. The thermal properties of the reference sample and those of the corresponding sample with nanofiller blends were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Two peaks were observed in the melting and crystallization temperatures. This shows that the EVA/LDPE is an immiscible polymer blend. The thermal stability of the blends was improved by the presence of HNTs and ATH-sil nanoparticles. Thermal degradation temperatures were shifted to higher values by the presence of hybrid nanofillers. Finally, the flammability of the compositions was assessed. Flammability as reflected by the limiting oxygen index (OI) was increased by the presence of HNT and ATH-sil nanofiller and a hybrid system of the nanoparticles.

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A Study of the Nitrogen-Containing Heterocycles on Copolyimide Properties for Proton Exchange Membranes

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.401-403.563 ◽

2013 ◽

Vol 401-403 ◽

pp. 563-566 ◽

Cited By ~ 1

Author(s):

Yu Han Li ◽

Wei Jian Wang ◽

Yu Fei Chen ◽

Lei Wang

Keyword(s):

Mechanical Properties ◽

Thermal Stability ◽

Proton Conductivity ◽

Water Uptake ◽

Main Chain ◽

Proton Exchange Membranes ◽

Proton Exchange ◽

Membrane Properties ◽

Dimensional Changes ◽

Sulfonated Polyimide

Containing pyrimidine and pyridine monomers were incorporated respectively into the main chain of a sulfonated polyimide in order to investigate the effect of nitrogen-containing heterocycles on membrane properties such as water uptake and proton conductivity. With increasing content of the nitrogen-containing heterocycles, water uptake of membranes and dimensional changes remarkable decrease. The copolymer showed higher thermal stability (desulfonation temperature up to 330 °C) and reasonable good mechanical properties. These membranes also showed higher proton conductivity, which was comparable or even higher than Nafion 117.

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