Patent ID: 7511089

Claim:
An alkali metal or alkaline earth metal salt of sulfonic acid of polyphenylene ether oligomer having the structural formula (1): wherein â€”[Oâ€”Xâ€”O]â€” has the structural formula (2): wherein each of R 2 , R 3 , R 4 , R 8 and R 9 which may be the same or different is a halogen atom, alkyl of up to 6 carbon atoms or phenyl, each of R 5 , R 6 and R 7 which may be the same or different is a hydrogen atom, halogen atom, alkyl of up to 6 carbon atoms or phenyl, â€”[Yâ€”O]â€” is a structure of one type having the structural formula (3) or a random array of structures of at least two types having the structural formula (3): wherein each of R 10 and R 11 which may be the same or different is a halogen atom, alkyl of up to 6 carbon atoms or phenyl, each of R 12 and R 13 which may be the same or different is a hydrogen atom, halogen atom, alkyl of up to 6 carbon atoms or phenyl, Z is a divalent organic group of 1 to 6 carbon atoms which may contain an oxygen atom, R 1 essentially contains a structure having the structural formula (4): R 1 may be, in part, replaced by hydrogen atoms or glycidyl groups, M is an alkali metal and/or alkaline earth metal, each of a and b is an integer of 0 to 100, and each of c and d is an integer of 0 to 20.