TY - JOUR
T1 - Imidazolium-Based Ionic Liquids as Initiators in Ring Opening Polymerization
T2 - Ionic Conduction and Dielectric Response of End-Functional Polycaprolactones and Their Block Copolymers
AU - Choi, U. Hyeok
AU - Mittal, Anuj
AU - Price, Terry L.
AU - Colby, Ralph H.
AU - Gibson, Harry W.
N1 - Funding Information:
The authors sincerely thank the U.S. Army Research Office for fi nancial support under Grant No. W911NF- 07-1-0452 Ionic Liquids in Electro-Active Devices (ILEAD) MURI. The authors thank Prof. Timothy E. Long (Virginia Tech) for providing polymer characterization facilities and Prof. James Runt (Penn State) for use of his dielectric equipment and guidance. The authors also extend their gratitude to Mr. Kim Harich (Virginia Tech) for the MALDI-TOF mass spectrum.
Publisher Copyright:
© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
PY - 2016/6/1
Y1 - 2016/6/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=84973279160&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84973279160&partnerID=8YFLogxK
U2 - 10.1002/macp.201500424
DO - 10.1002/macp.201500424
M3 - Article
AN - SCOPUS:84973279160
SN - 1022-1352
VL - 217
SP - 1270
EP - 1281
JO - Macromolecular Chemistry and Physics
JF - Macromolecular Chemistry and Physics
IS - 11
ER -