Poly(N-tosyl-ethylene imine-alt-ethylene sulfide) has been synthesized by thiol-ene photopolymerization between N,N-bis(2-mercaptoethyl)-4-methylbenzenesulfonamide and 4-methyl-N,N-divinylbenzenesulfonamide. Its weight-average molecular weight was determined by static light scattering to be 2.8 × 104. The alternating copolymer has –SH and –CH=CH2 end groups and exhibits high solubility in common organic solvents such as chloroform, tetrahydrofuran, acetone, and dimethyl sulfoxide. The N-tosylated copolymer was deprotected to yield poly(ethylene imine-alt-ethylene sulfide), which is fully soluble in dimethyl sulfoxide, acetic acid, and ethanol. Both N-tosylated and deprotected polymers are hydrophobic, and the former and latter polymers are thermally decomposed at 272 and 244 °C, respectively.