Star-shaped　thermo-responsive　block　copolymers　were　synthesized　by　atom　transfer　radical　polymerization　(ATRP)　of　a　hydrophilic　cationic　monomer　(2-(dimethylamino)ethyl　methacrylate)　(DMAEMA)　and　a　zwitterionic　monomer　(sulfobetaine　methacrylate)　(SBMA)　from　cyclodextrin　with　multi-initiator　sites.　These　star　polymers　with　different　arm　lengths　and　arm　densities　were　characterized　by　1H　NMR　and　GPC.　Thermo-responsive　behaviors　of　the　star　polymers　were　investigated　not　only　at　different　pH　values,　but　also　at　different　NaCl　concentrations.　The　size　and　morphology　of　the　star　polymers　and　their　aggregates　were　measured　by　dynamic　light　scattering　and　transmission　electron　microscopy.　The　star　polymers　showed　only　upper　critical　solution　temperature　(UCST)　behavior,　since　zwitterionic　PSBMA　outer　blocks　shielded　the　lower　critical　solution　temperature　(LCST)　behavior　of　PDMAEMA　midblocks.　However,　PDMAEMA　blocks　had　significant　influence　on　the　thermo-induced　associations　of　the　star　polymers,　and　resulted　in　a　tunable　critical　aggregation　temperature　with　varying　arm　density　or　pH　value　of　solution.　Moreover,　enhanced　thermo-responsive　behavior　was　also　obtained　at　NaCl　concentrations　up　to　more　than　20　mM,　which　is　much　higher　than　those　reported　before.　Finally,　biocompatibility　evaluations　showed　that　the　star　polymers　could　effectively　reduce　the　adsorption　of　BSA　in　PBS　solution　and　had　insignificant　cytotoxicity　to　MCF-7　cells.　These　results　demonstrate　they　are　good　candidates　for　potential　applications　in　biomedically　relevant　fields.　This　journal　is　©　The　Royal　Society　of　Chemistry　2015.