Magneto-active polymers are polymer-based composites consisting of magnetizable micro-particles embedded in an elastomeric matrix material. The presence of magnetic particles provides strong tunability to the stiffness and damping properties of the polymeric composites under the magnetic field. We propose here a novel free energy-based phenomenological modeling for magneto-active polymers. Coupled mechanical and magnetization constitutive equations are derived by considering magneto-viscoelasticity in a finite deformation framework. The model calibration takes into account the demagnetization effect, which depends on the specimen size, shape, and its own magnetization. The model prediction is verified with the available experimental data. Finally, a coupled simple shear problem is solved to demonstrate the influence of magnetic field on the Poynting effect. Classical nonlinear soft elastic material shows positive Poynting effect, i.e., shearing planes try to expand. We found the possibilities of field-induced reverse or negative Poynting effect in shear for magneto-active polymers. Such a negative Poynting effect could potentially affect a very diverse range of applications from the performances of miniature sensors and actuators to controlled drug delivery.

磁活性聚合物是聚合物基复合材料，由嵌入弹性基体材料中的可磁化微粒组成。磁性颗粒的存在为聚合物复合材料在磁场下的刚度和阻尼特性提供了很强的可调性。我们在这里提出了一种新的基于自由能的磁活性聚合物的现象学建模。通过在有限变形框架中考虑磁粘弹性，推导出耦合的机械和磁化本构方程。模型校准考虑了退磁效应，退磁效应取决于试样的尺寸、形状和自身的磁化强度。模型预测得到了可用的实验数据的验证。最后，解决了耦合的简单剪切问题，以证明磁场对坡印廷效应的影响。经典非线性软弹性材料表现出正坡印廷效应，即剪切平面试图扩展。我们发现了磁场诱导的反向或负 Poynting 效应在磁活性聚合物的剪切中的可能性。这种负面的坡印廷效应可能会影响从微型传感器和执行器的性能到受控药物输送的各种应用。