Effect of Molecular Weight of Methylphenylsiloxy-Containing Vinyl-Functionalized Terpolysiloxanes on Their UV-Activated Crosslinking by Hydrosilylation and Mechanical Properties of Crosslinked Elastomers.

Effects of molecular weight of methylphenyl-containing vinylsiloxy-functionalized terpolysiloxanes on their UV-activated crosslinking by hydrosilylation at room temperature in air, shelf life stability of "all-in-one" pastes prepared from them for additive manufacturing, and mechanical properties of the resulting crosslinked elastomers, are investigated. It is found that while rheology of pastes containing base polymers, trimethylsilylated silica fillers, and thixotropic additives is not significantly affected by the base polymer molecular weight but is dominated by the filler concentration, the pastes based on higher molecular weight polymers exhibit faster crosslinking (corresponding to higher catalyst turnover numbers) and their crosslinked elastomers show transient strain-induced crystallization. The latter appears in networks from terpolymers with degrees of polymerization (DP) of 240 and above (corresponding to about one half of the critical polydimethylsiloxane chain length for entanglement formation of DP = 460), within the temperature range of -80 to -30 °C, characteristic for polydimethylsiloxane melting transition. It is believed that this is the first time an observation of this chain length effect is reported for polysiloxane elastomers and that the properties reported herein can be expected to have major implications on the application potential of these polymers in both additive manufacturing and performance of their elastomers at sub-ambient temperatures.

High-Performance Flexible Supercapacitors obtained via Recycled Jute: Bio-Waste to Energy Storage Approach.

In search of affordable, flexible, lightweight, efficient and stable supercapacitors, metal oxides have been shown to provide high charge storage capacity but with poor cyclic stability due to structural damage occurring during the redox process. Here, we develop an efficient flexible supercapacitor obtained by carbonizing abundantly available and recyclable jute. The active material was synthesized from jute by a facile hydrothermal method and its electrochemical performance was further enhanced by chemical activation. Specific capacitance of 408 F/g at 1 mV/s using CV and 185 F/g at 500 mA/g using charge-discharge measurements with excellent flexibility (~100% retention in charge storage capacity on bending) were observed. The cyclic stability test confirmed no loss in the charge storage capacity of the electrode even after 5,000 charge-discharge measurements. In addition, a supercapacitor device fabricated using this carbonized jute showed promising specific capacitance of about 51 F/g, and improvement of over 60% in the charge storage capacity on increasing temperature from 5 to 75 °C. Based on these results, we propose that recycled jute should be considered for fabrication of high-performance flexible energy storage devices at extremely low cost.

A comparative study of amphiphilic PAMAM dendrimers at the air-water interface with different hydrophobe attachment groups.

Generation 0 through 5 polyamidoamine (PAMAM) dendrimers with three different types of groups connecting to hydrophobic C12 tails and one type of group connecting to C18 tails were synthesized and studied as monolayers at the air-water interface with a Langmuir trough. The molecular areas were significantly influenced by the size and the type of connecting group. Higher-generation (e.g., G4 and G5) amphiphilic PAMAMs with amide connecting groups were more responsive to changes in compression rate and subphase temperature and less stable than the corresponding opened epoxide- or ester-connected counterparts. Intramolecular (and possibly also intermolecular) attractive hydrogen-bond interactions between the amide connectors are proposed as the reason for this behavior.