Polyphenylene ether, production method of the same, thermosetting composition, prepreg, and laminate

A polyphenylene ether comprising a repeating unit derived from a phenol of the formula (1):

• (in the formula (1), R13 is an optionally substituted saturated or unsaturated hydrocarbon group having a carbon number of 15, R11 and R12 are each independently one of a hydrogen atom, a linear saturated hydrocarbon group having a carbon number of 1 to 12, and substituents represented by the following formula (3), where R11 and R12 cannot be both hydrogen atoms):
• (in the formula (3), each R31 is independently an optionally substituted linear alkyl group having a carbon number of 1 to 8, or atoms in the two R31 are bonded together to form a cyclic alkyl group with a carbon number of 1 to 8, each R32 is independently an optionally substituted alkylene group having a carbon number of 1 to 8, b is each independently 0 or 1, and R33 is a hydrogen atom, an optionally substituted alkyl group having a carbon number of 1 to 8, or an optionally substituted phenyl group).