Poly(isoprene) (PI) with pendant functional groups was successfully synthesized by thiol-ene addition reaction under 365 nm UV irradiation, and the functionalized PI was further modified and used to prepare graft copolymers with "V"-shaped side chains. First, the pendant -SCH2CH(OH)CH2OH groups were introduced to PI by thiol-ene addition reaction between 1-thioglycerol and double bonds, and the results showed that the addition reaction carried out only on double bonds of 1,2-addition isoprene units. After the esterification of hydroxyl groups by 2-bromoisobutyryl bromide, the forming macroinitiator was used to initiate the atom transfer radical polymerization (ATRP) of styrene (St) and tert-butyl acrylate (tBA), and the graft copolymers PI-g-PS2 and PI-g-PtBA(2) or PI-g-PAA(2) (by hydrolysis of PI-g-PtBA(2)) were obtained, respectively. It was confirmed that the graft density of side chains on PI main chains could be easily controlled by variation of the contents of modified 1,2-addition isoprene units on PI. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3797-3806, 2010