Template Effect On Stability Of Twist Structure Liquid Crystals

Twist structure liquid crystals(LCs)include cholesteric liquid crystal(CLC),blue phase liquid crystal(BPLC)and sphere phase liquid crystal(SPLC).The CLCs are composed of achiral nematic liquid crystal(NLC)and chiral molecules,and has a self-assembled one-dimensional twist structure.Blue phase exist between isotropic phase and cholesteric phase.In natural state,its temperature range is small,usually 1 to 2 ℃.BPLCs consist of self-assembled two-dimensional double-twisted cylinders(DTCs)and defects among them.Sphere phase liquid crystals(SPLCs)are composed of three-dimensional twist spheres(3-DTSs)and disclination among 3-DTSs.Sphere phase usually observed between isotropic phase and cholesteric phase or between isotropic phase and blue phase due to its weak thermal stability of the disclination among the 3-DTSs,its temperature range is small.By irradiating polymer CLC,polymer BPLC and polymer SPLC mixture with ultraviolet light,respectively,we obtained polymer-stabilized CLC(PS-CLC),polymer-stabilized BPLC(PS-BPLC)and PS-SPLC.Putting it into organic materials to wash out unreacted polymer monomer molecules,remaining LCs and chiral agents,so we prepared CLC templates,BPLC templates,and SPLC templates,and we study their reconstruction characteristics.In order to investigate CLC template effect on stability of multi-phase twist structure LCs,a CLC of different pitch was refilled into it,the refilling CLC and intrinsic CLC can co-exist in the template.And a BPLC or a SPLC of different pitch was refilled into CLC template,only the intrinsic CLC appeared.In order to investigate BPLC template effect on stability of multiphase twist structure LCs,a CLC of different pitch was refilled into it,both the refilling CLC and intrinsic BPLC appeared in the template.However,a BPLC or a SPLC of different pitch was refilled into BPLC template,only the intrinsic BPLC appeared.In order to investigate SPLC template effect on stability of multi-phase twist structure LCs,a CLC of different pitch was refilled into it in room temperature,both the refilling CLC and T-SPLC appeared in the template,but when a CLC of different pitch was refilled into SPLC template in isotropic phase,then slowly cooled down to room temperature,only the intrinsic SPLC appeared.And a BPLC or a SPLC of different pitch was refilled into SPLC template,only the intrinsic SPLC appeared.To CLCs,the templating process may only reconstruct the one dimensional twist structure but not improve the stability,because there are no defects exist among twist structures.As to BPLCs and SPLCs,the templating process may not only reconstruct the two-dimensional DTCs and3-DTSs structure,respectively,but also improve the thermal stability of BPLCs and SPLCs,because the polymer templates can occupy the position of the defects and provide the anchoring energy.Therefore,we proposed strong and weak relationship between the thermal stability of three twist structure LCs and the thermal stability of TCLC,T-BPLC and T-SPLC.It was found that the thermal stability of CLC is very close to that of T-CLC,T-BPLC and T-SPLC.By templating technology,a twist structure LCs film device of multipitch or multi-phase can be prepared,which provides the feasibility for the applications in optical communication,display,and LC lasing.