A polyphenylene ether resin modified with benzoxazine, a method for producing the same, and a substrate material for a circuit board are provided. The polyphenylene ether resin modified with the benzoxazine has a structural formula as follows:

##STR00001## in which R represents a chemical group that is located between two hydroxyphenyl functional groups of a bisphenol compound, and n is an integer between 3 and 25, inclusive.

Disclosed are polymers containing a backbone comprising alternating N-protected hydroxymethylaniline units (spacer) and linker units.