In‐situ photopolymerization of an oriented liquid‐crystalline acrylate

Abstract

Abstract The photoinitiated polymerization of 4‐biphenylyl 4‐(6‐acryloyloxyhexyloxy)benzoate ( 1 ) in its oriented liquid‐crystalline state was studied. Monomer 1 has a thermotropic nematic phase between 88°C and 98°C, a monotropic nematic phase between 76°C and 88°C, and a monotropic smectic phase below 76°C. The orientation of 1 was established in a glass cell provided with a rubber polyimide coating and characterized by birefringence measurements. During polymerization both the birefringence and the liquid‐crystalline transition temperatures increase, indicating that the orientation was maintained. The oriented poly( 1 ) is polycrystalline at room temperature, becomes smectic at 90°C, nematic at 172°C, and isotropic at 190°C. The order parameter of the nematic poly( 1 ) is lower than that of the nematic monomer 1 at equal reduced temperatures.