Patent ID: 8603533

Claim:
A polymersome comprising a block-type alkylene oxide derivative represented by the following formula (I) as the membrane component: R 1 O-[(EO) l (AO) m (EO) n ]—R 2 (I) wherein AO is an oxybutylene group, EO is an oxyethylene group, m and 1+n are the average addition mole numbers for the oxybutylene group and the oxyethylene group, respectively, and 1≦m≦70, 1≦l+n≦70; the percentage of the oxyethylene groups with respect to the sum of the oxybutylene groups and the oxyethylene groups is 20 to 80 mass %; and R 1 and R 2 are identical or different hydrocarbon groups having 1 to 4 carbon atoms.