Broadband reflection characteristic of polymer-stabilised cholesteric liquid crystal with pitch gradient induced by a hydrogen bond

Abstract

A polymer-stabilised cholesteric liquid crystal (PSChLC) was fabricated by ultraviolet (UV) induced polymerisation of photopolymerisable acrylate monomers mixed in a cholesteric liquid crystal (ChLC). A polymer network with a concentration gradient, which was induced by UV light absorption of dye along the propagation direction, was formed. A hydrogen bond, arising between the polymer network with a concentration gradient containing carboxyl as proton donors and chiral dopant (CD) as proton acceptors, induced a pitch gradient in PSChLC and then, as a consequence, broadband reflection. The broadband reflection is associated with the concentration and the composition of photopolymerisable acrylate monomers, the concentration of CD and the polymerisation temperature. Examining the morphologies of the polymer network by scanning electron microscopy, the helix structure and pitch gradient were verified, confirming the pitch gradient of the PSChLC and revealing the essence of the formation of broadband reflection.