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Choi U.H.,Pennsylvania State University | Choi U.H.,Korea Institute of Materials Science | Mittal A.,Virginia Polytechnic Institute and State University | Mittal A.,Momentive Performance Materials Pvt. Ltd. | And 6 more authors.
Electrochimica Acta | Year: 2015

The dependences of the glass transition temperature and the dielectric constant on molecular volume of the repeat unit for polymerized ionic liquids, the monomers they were polymerized from and simple ionic liquids, are reviewed and compared. The ionic conductivities of these materials and the frequencies at which ionic rearrangements occur are shown to be controlled by their glass transition temperatures. The ionic conductivity is proportional to the product of dielectric constant and ionic rearrangement frequency, with the proportionality constant determined by the molecular volume of the repeat unit. © 2014 Elsevier Ltd. All rights reserved.


Choi U.H.,Pennsylvania State University | Choi U.H.,Korea Institute of Materials Science | Mittal A.,Virginia Polytechnic Institute and State University | Mittal A.,Momentive Performance Materials Pvt. Ltd. | And 3 more authors.
Macromolecular Chemistry and Physics | Year: 2016

Imidazolium alcohols, [R-Im-Z-OH]+[X]-, are investigated as initiators for ring opening polymerization (ROP) of ϵ-caprolactone (CL). Two monomeric imidazolium alcohols {I [R = HOOC(CH2)5, Z = (CH2)11, X = Br] and III [R = n-Bu, Z = (CH2CH2O)3CH2CH2, X = bis(trifluoromethylsulfonyl)imide (TFSI)]} are successfully utilized as initiators for ROP of CL, yielding corresponding polycaprolactones (PCL) Ia-Br and IIIa-TFSI. The oligoester II derived from I also acts as an initiator, providing block copolymer IIa-Br. By anion exchange Ia-Br and IIa-Br are converted to Ia-TFSI and IIa-TFSI. The TFSI polymers have lower glass transition temperatures (Tg), resulting in higher conductivity, compared to the Br polymers. The ionic conductivities of the PCL block copolymers are higher than those of the PCL homopolymers, despite the similar Tg, because of their higher ionic content. Their static dielectric constants (ϵs) increase linearly with ion content and exhibit the temperature dependence expected by Onsager, in the liquid state. The semicrystalline PCL homopolymers, upon crystallization, undergo a significant increase in ϵs, owing to a Maxwell-Wagner-Sillars interfacial polarization. The present results demonstrate that with proper design, block copolymers have the potential to provide high ionic conductivities combined with good mechanical strength, key attributes for application of these materials in mechanical actuators. End-functional polycaprolactones and their block copolymers containing ionic liquid functionalities are synthesized by ring-opening polymerization. The ionic conductivity and dielectric constant are investigated, revealing that with proper design, block copolymers have the capacity to provide high ionic conductivity combined with good mechanical strength, key attributes for application of these materials in electroactive ionic actuators and sensors. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Saxena A.,Momentive Performance Materials Pvt. Ltd | Dasgupta D.,Momentive Performance Materials Pvt. Ltd | Bhat S.,Momentive Performance Materials Pvt. Ltd | Tiwari S.,Momentive Performance Materials Pvt. Ltd | And 2 more authors.
Journal of Applied Polymer Science | Year: 2014

This piece of contribution highlights the profound effect of unique mesoscale morphology of tailor made nanosilica assembly (SS-Silica), synthesized by sol-gel route, on the mechanical and dynamic rheological properties of platinum catalyzed addition-cured silicone elastomers. While commercial colloidal nanosilica (CS Silica) is used as the control nanofiller representing particulate morphology, the tailor-made SS-Silica having highly percolated network structure offers 10-fold increase in storage modulus of the uncured reactive PDMS precursor nanocomposite with stable dynamic rheological behavior and more than 180% enhancement in tensile strength of resulting liquid silicone rubber (LSR) produced on curing, as compared to colloidal silica of commercial origin. © 2013 Wiley Periodicals, Inc.

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