Well-defined amphiphilic telechelics incorporating polyhedral oligosilsesquioxane (POSS) were synthesized by direct urethane linkage between the diol end groups of poly(ethylene glycol) (PEG) homopolymers and the monoisocyanate group of POSS macromers. The hydrophobicity of the amphiphilic telechelics was varied by using a series of PEG homopolymers of increasing molecular weight, resulting in control over molecular architecture by hydrophilic/hydrophobic balance. The synthesized amphiphilic telechelics were characterized by H-1 NMR, FT-IR GPC, DSC, and TGA, showed a relatively narrow and unimodal molecular weight distribution (M-w/M-n < 1.1) that had close to 2.0 end groups per PEG chain, and revealed strongly modified thermal behavior. Amphiphilic telechelics with POSS contents of 19.8, 23.6, 40.7, 52.7, and 68.1% depending on the molecular weights of PEG homopolymers could be obtained. Modification to crystallization behavior is observed and attributed to the bulkiness of POSS groups with respect to crystalline lamellae dimensions.