Photopolymerization of Reactive Mesogens

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Abstract
Summary: The photopolymerization of two reactive mesogens with photopolymerizable acrylate endgroups, the methyl substituted 1,4‐phenylene‐bis{4‐[6‐(acryloyloxy)hexyloxy]benzoate} 1 and acrylic acid 6‐{4‐[6‐(6‐acryloyloxyhexyloxy)naphthalen‐2‐yl]‐phenoxy}hexyl ester 2 has been investigated using Photo‐DSC measurements. Photocrosslinking of 1 in the nematic phase at 100 °C leads to a final conversion of 87% of the acrylate groups. It is possible to perform photopolymerization with very small amounts of photoinitiator. Even with 0.001% (10 ppm) of photoinitiator, 47% of the acrylate groups polymerize within 15 min. The polymerization of the reactive mesogen 2 proceeds faster in the smectic A phase at 100 °C compared to the isotropic phase at 120 °C and leads to a higher conversion of 75%. This can be explained by an increased local concentration of the acrylate groups between the layers of the smectic cores. Photopolymerization of reactive mesogens. magnified image Photopolymerization of reactive mesogens.