Abstract
Organic material characteristics of volume change and stress generation have attracted the attention of many researchers aiming to develop chemomechanical systems such as artificial muscles and polymer engines having the advantages of high energy density and silent operation. Although polymer gels offer a relatively large actuator stroke, their mechanical properties are relatively poor and the working temperature is relatively low, often limited by the evaporation of liquid if contained. We have developed an iodine-treated poly(vinyl alcohol) having extraordinarily large vapor-induced deswelling stress reaching 59 MPa, which is one to two orders of magnitude greater than those of ordinary polymer gels. Furthermore, this material has extremely large volumetric and gravimetric energy densities reaching 1.3 × 106 J m−3 and 9.6 × 102 J kg−1, respectively, and an elastic modulus of a few GPa and is heat-resistant to at least 200 °C. The high performance of this material can be demonstrated by a jump of a film. © 2014 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1357–1365
Highlights
Many types of organic materials have been developed which experience volume change and generate stress in response to various stimuli such as light, electric field, heat, pH, and chemical substances.[1,2,3,4,5,6,7,8,9,10,11] Among various mechanisms of volume change, swelling of polymer gels is caused by a mechanism similar to that responsible for dissolution of polymers in solvents
We have developed a crosslinked structure that can prevent this significant loss in rigidity without sacrificing swelling ability by an iodine treatment of poly(vinyl alcohol) (PVA)
It has been reported that the iodine treatment of PVA in combination with heat treatment produces polyene due to dehydration and aromatic rings and crosslinks due to intermolecular ring closure of polyene.[16]
Summary
Many types of organic materials have been developed which experience volume change and generate stress in response to various stimuli such as light, electric field, heat, pH, and chemical substances.[1,2,3,4,5,6,7,8,9,10,11] Among various mechanisms of volume change, swelling of polymer gels is caused by a mechanism similar to that responsible for dissolution of polymers in solvents. The actuation stress of polymer gels reported to date is up to an order of 1 MPa.[19] A poly(acrylonitrile) gel fiber, for example, produces a contraction stress of about 2 MPa by changing pH.[20] The actuation stress of muscles is much lower and is in the range of 0.1–0.4 MPa.[21] The contraction stress and energy densities of the iodine-treated PVA fiber developed in the current study are much greater than the values so far reported for polymer gels.
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