Surfactant and preparation method therefor

A surfactant having a formula (I):

• R1—O-(Poly)n-X—Ya−·a/bMb+;
• (I)
• wherein:
• R1 is any one of C1-C50 aliphatic group or aromatic group;
• each occurrence of group Poly, equal to or different from each other, is independently selected from the group represented by formula (Ru—O)m;
• in each group Poly, the each occurrence of group Ru, equal to or different from each other, is independently selected from C2-6 linear or branched alkylene group, with the proviso that:
• the group Ru in at least a part of the groups Poly is selected from butylene, and there is a spacer group L between at least a part of the groups Poly;
• wherein the L is a group containing a heteroatom and two free ends having 0 to 30 carbon atoms, wherein the heteroatom is N and/or S;
• n is a number from greater than 0 to 300;
• for each type of group (Ru—O), m is independently a number from greater than 0 to 100;
• X is any one of alkylene, alkenylene or arylene containing 1-10 carbon atoms;
• Y is an anionic group;
• M is a cation or cationic group maintaining charge balance of the formula;
• and
• a is the absolute value of the valence of Y, and b is the absolute value of the valence of M.