Provided herein are block copolymers comprising a hydrophilic polymer segment and a hydrophobic polymer segment, wherein the hydrophilic polymer segment comprises a polymer selected from the group consisting of: poly(ethylene oxide) (PEO), poly(methacrylate phosphatidyl choline) (MPC), and polyvinylpyrrolidone (PVP), wherein the hydrophobic polymer segment comprises wherein R′ is —H or —CH3, wherein R is —NR1R2, wherein R1 and R2 are alkyl groups, wherein R1 and R2 are the same or different, wherein R1 and R2 together have from 5 to 16 carbons, wherein R1 and R2 may optionally join to form a ring, wherein n is 1 to about 10, and wherein x is about 20 to about 200 in total. Also provided are pH-sensitive micelle compositions for therapeutic and diagnostic applications.