Thermoresponsive switching in an adaptive polymer-stabilized polymorphic liquid crystal window without surface orientation treatment

We present a self-sensing smart window based on thermally passive control of polymer-stabilized cholesteric liquid crystal (PSCLC), whose transmission varies through the smectic A (SmA)-chiral nematic (N*) phase transition. In the temperature range corresponding to the SmA phase, the PSCLC cell exhibit a transparent state. Conversely, the cell in the N* phase adopts a highly hazy appearance caused by the focal conic texture of the cholesteric liquid crystal (LC) molecules. Upon cooling the composite from the N* phase to the SmA phase, the interactions between the LC molecules and the polymer network restore the vertical orientation of the mesogenic molecules for the revertible transparency. An advantageous characteristic of this PSCLC cell is the absence of an aligning layer and surface treatment because the polymer network in the LC bulk eliminates the necessity for coordination layers. Our findings indicate that the photocurable bifunctional LC monomer RM257 alone is insufficient for the formation of stable vertical alignment following ultraviolet curing for photopolymerization. With a minimal quantity of the trifunctional monomer TMPTA not only efficaciously elevates the crosslinking density and stability of the PSCLC system but also reduces the total amount of polymer required. Moreover, the PSCLC system boasts an exceptionally high contrast ratio (of 420), a value that is challenging to attain in a conventional PSCLC system. With self-adaptive properties in response to ambient temperature changes, the proposed device holds significant potential for smart window applications in both buildings and vehicles.