In‐situ photopolymerization of an oriented liquid‐crystalline acrylate

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Abstract
The photoinitiated polymerization of 4‐biphenylyl 4‐(6‐acryloyloxyhexyloxy)benzoate (1) in its oriented liquid‐crystalline state was studied. Monomer1has 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 of1was 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 monomer1at equal reduced temperatures.