Electrostrictive graft elastomers

Su J, Hales K, Xu TB (2003) Composition and annealing effects on the response of electrostrictive graft elastomers. Proc SPIE 5051 191... 

Su J, Harrison IS, Clair TLS, Bar-Cohen Y, Leary S (1999) Electrostrictive graft elastomers and applications. Mater Res Soc Symp Proc 600 131... 

In the case of polymeric elastomers exhibiting a large electric field-induced strain, two intrinsic mechanisms are considered as primary contributors electrostriction and the Maxwell stress effect. The contributions from both mechanisms exhibit a quadratic dependence with an applied electric field. For the newly developed electrostrictive graft elastomers, more than 95 % of the electric field-induced strain response is contributed by the electrostriction mechanism, while the contribution from the Maxwell stress effect is less than 5 %. Due to the relatively high elastic modulus ( 0.55 GPa), the grafted elastomer also exhibits a high elastic energy density of 0.44 MJ/m. ... 

Slichter (1959) Molecular motion in polyamides. J Polym Sci A 35(128) 77-92 Su (1992) Ferroelectricity and piezoelectricity of nylon 11-PVF2 bilaminates. Internal Technical report, Rutgers, The State University of New Jersey Su J et al (1999) Electrostrictive graft elastomers and applications. In Proceedings of MRS Symposium, vol 600, pp 131-136, MRS Conference Publication Su J et al (2003) Electrostrictive graft elastomers, U.S. Patent No. 6,515,077, 4 Su J et al (1995) Ferroelectric and piezoelectric properties of nylon 1 l/poly(vinylidene fluoride) bilaminate films. J Polym Sci Part B Polym Phys 33 85... 

Wang Y et al (2003) Two-dimensional computational model for electrostrictive graft elastomer. Proc SPIE 5051 100-111, SPIE Publisher... 

Electrostrictive polymers have a spontaneous electric polarization. Electrostriction results from the change in dipole density of the material. These polymers contain molecular or nanocrystaUine polarizations that align with an applied electric field. PVDF copolymers with nano-sized crystalline domains, electrostrictive graft copolymers, and liquid crystal elastomers fall under this category. 

Fig. 1.6 Electrostrictive graft copolymer consisting of P(VDF-TrFE) main chains and PVDF grafts. Polar PVDF units (pink) aggregate and form crystallites that serve as polarizable moieties for actuation and as physical crosslinks between elastomer chains [113]. J. Su 2003, reprinted with permission...

To understand the mechanisms of the electrostriction in the G-elastomers, a model has been established (Wang et al. 2003). The model simulation indicated that the mechanisms of the electric field-induced strain in the electrostrictive G-elastomers are attributed to the rotation of the polar crystal domains that formed by grafted molecular chains and the reorientation of the flexible backbone chains when an electric field is applied. 

A relatively newer finding is that of elastomeric electrostrictive systems are possible that give strains up to 4% (13). As illustrated in Figure 4, on application of an electric field there is an increase in area as opposed to the one dimensional response of ceramics. The relatively low tensile modulus of elastomers, typieally around 50 MPa, restricts the ability to impose high stresses but nevertheless opens up exciting possibilities in elastomerie applications in packaging and fibers. The eombination of fimctionahty of electrostrictive behavior with say transport is examined later. Chemistry approaehes of graft and block polymerizations will rapidly expand and ereate new possibihties. 

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