Synthesis and characterization of poly(vinyl alcohol) containing long-chain alkoxy coumarins

Abstract

Two coumarins, 5,7-dihydroxy-4-methylcoumarin and 6,7-dihydroxy-4-methylcoumarin, have been used in this study. The former was synthesized via the Pechmann reaction, while the latter is commercially available. Each of them was alkylated with butyl bromide or octyl bromide. In each alkylation, two monoalkoxy- and one dialkoxycoumarins were obtained for the first coumarin, and one monoalkoxy- and one dialkoxycoumarin were yielded for the second coumarin. Each of six monoalkoxy coumarins was further alkylated with 1,3-dibromopropane. It was found that two 7-alkoxy-5-hydroxy-4-methylcoumarins and two 5-alkoxy-7-hydroxy-4-methylcoumarins could react to yield four (3'-bromo)propoxycoumarins. In addition, two parent dihydroxy-4-methylcoumarins were also reacted with 1,3-dibromopropane for comparison. Finally, seven (3'-bromo)propoxycoumarins were reacted with poly(vinyl alcohol) (PVA). However, 6-hydroxy-4-methyl-7-(3'-bromo)coumarin did not reacted and only six products were obtained after dialysis and freez-drying. All synthesized compounds were characterized by FTIR, 1H-NMR and UV spectroscopy. In the photoresist testing, four out of six polymersgave patterns on glass slides after irradiation and developing in hot water. The results revealed that two PVA containing 7-butoxy-4-methyl-5-(3'-bromo)propoxycoumarin and PVA containing 5-butoxy-4-methyl-7-(3'-bromo)propoxycoumarin were the most acceptable negative photoresist.