亲爱的志刚，

感谢您的关注。我们可以简单地把LCE看成两部分:液晶和聚合物网络。动态共价化学通过交换反应将LCE从多畴转化为单畴。LCE的致动特性归因于液晶的相变。当我们想要使用LCE作为执行器时，LCE应该是热固性的，没有任何交换反应。否则，在几个周期后，作动特性将消失。

我们尝试了几种动态共价键来制备LCE。像RM257一样，大多数液晶具有液晶各向同性温度(Ti)。

对于热触发的动态共价键，如环氧-酸体系，它们具有反应温度(Tr)。Tr应该比Ti大得多。我们可以将LCE从多域处理到Tr以上的单域，当冷却时，单域状态是固定的。 When the monodomain LCE is used as actuator around Ti, the polymer network is thermoset and doesn't rearrange. The actuation behavior results from the phase transition of liquid crystal mesogens. Ji and her coworkers discussed it in Ref [19].

If Tr is close or lower than Ti, when LCE is heated above Ti, it will contract. However, the exchange reaction also happens andhe polymer network rearranges. After several times or heating above Ti for enough time. LCE will change back to polydomain state. The Tr for imine chemistry and olefin metathesis are lower than 80 oC. They are not suitable for RM257-type liquid crystal mesogens. We tried imine chemistry and didn't obtain monodomain LCE.

The disadvantage of thermo-triggered DCC for LCE is that when we heat LCE above Tr which is much larger than Ti, LCE will contract and generate large stress. Usually, people use creep experiment to align it slowly. It is diffcult to control the actuation strain, stress.

For photo-triggered DCC based LCE, the situation is much simpler. In Ref 24, Bowman and his coworkers reported RAFT-based DCC to make LCE. The RAFT exchange reaction can be triggered by light in the presence of photoinitiator. After initiaor is consumed, LCE is thermoset and can not change from polydomain to monodomain.

Disulfide exchange reaction can be triggered either under heat and UV light. The reaction temperature (Tr) depends on the substitute groups (R), catalyst and base. In our work, Tr for disulife exchange reaction is much higher than Ti of liquid crystal mesogens we used. So disulfide LCE can be processed through heating.

Disulfide exchange reaction can also be triggered under UV light without any photoinitiator. It can be processed for many times and stored for long time.

Best,

Zhijian