Structure-property relationship of vinyl-terminated oligo(2,6-dimethyl-1,4-phenylene ether)s (OPEs): Seeking an OPE with better properties

Vinylbenzyl ether-terminated oligo(2,6-dimethyl-1,4-phenylene ether) (1) has been commercialized by Mitsubishi Gas Chemical in the name of OPE-2St. OPE (1) is used in high-frequency printed circuit board due to its low-dielectric characteristic after curing. However, for thermoset of (1), there is room for property improvement in thermal mechanical property, dielectric property, oxygen permeation resistance, and so on. In this work, we report the preparation of three new oligo(2,6-dimethyl-1,4-phenylene ether)s: the vinyl benzoate terminated OPE (2), the 3,5-bis(vinylbenzyl ether)benzyl ether-terminated OPE (3), and the 3,5-bis(vinylbenzyl ether)benzoate-terminated OPE (4), and compare their fundamental materials properties with the vinylbenzyl ether-terminated OPE (1). We discussed the effect of the number of vinyl groups (two or four) and the linker (benzyl ether or benzoate) on the properties of the four OPE thermosets. Through property evaluation and data analyses, we found that the thermoset of (4) show the highest T-g, modulus, oxygen permeation resistance, dimensional stability, and the lowest water absorption, and dielectric constant. We also found that the toughness of thermoset of (4) can be significantly enhanced by the copolymerization with epoxy resin (HP7200) through the exchange reactions of benzoate and epoxy groups. In short, through properties comparison of four thermosets of (1-4), we demonstrate that (4) is a promising material for high-frequency printed circuit board.