Disclosed is a flexible maleimide polymer. The flexible maleimide polymer includes a reaction product of reactants (a)-(c). The reactant (a) is maleimide, a compound with a structure represented by Formula (I), a compound with a structure represented by Formula (II), or combinations thereof wherein R1 is —(CH2)10—CO2H, and R2 is H, OH, SO3Na, NO2, CN or CO2H. The reactant (b) is a compound with a structure represented by formula (III) wherein A is R3 is H or methyl group, x is between 1-12, R4 is H or methyl group, and y and z are both between 1-5. The reactant (c) is a compound with a structure represented by formula (IV), or a compound with a structure represented by formula (V) wherein R5 and R6 are independent H or C1-4 alkyl group.