Impact of composition on properties of liquid crystal elastomer films: a comprehensive study

A series of elastomeric films were synthesized using [1,1'-biphenyl]-4,4'-diyl bis(undec-10-enoate) (ML) and dodecane-1,12-diyl bis(undec-10-enoate) (MS) as crosslinking agents, and pentaerythritol tetra(3-mercaptopropionate) (P') as a crosslinking center. This series, namely P'xLySz, consists of varying molar ratios of P', ML, and MS. The polymerization reaction is rapid and easy to perform. Except for P'6L0S12, the other elastomer films in the P'xLySz series all show liquid crystal properties. The increase of ML is beneficial to improving the LC range and shape-memory performance of the LCE films. P'6L12S0 exhibited excellent reversible shape-memory performance. During this process, P'6L12S0 can lift and lower a weight 110 times its own weight, and the shape recovery rate (Rr) reaches 100%. P'6L0S12 had the highest breaking strength (7.6 MPa) while P'6L8S4 displayed the highest breaking elongation (463%). The regularity of the molecular chains has a significant influence on both the breaking strength and breaking elongation. The films in this series displayed excellent thermal stability (the temperature at which 5% weight loss occurred is around 350°C).