In order to study the self-assembly of block copolymer grafted from graphene oxide (GO) by the fluorescence of GO, poly(epsilon-caprolactone) (PCL)-block-poly(dimethyl aminoethyl methacrylate) (PDMAEMA) is grafted from its surface using consecutive ring opening (ROP) and atom transfer radical polymerization (ATRP). GO-g-(PCL13-b-PDMAEMA(117)) (GPCLD) at pH 9.2 exhibits cloud point (T-c) at 32 degrees C. At pH 9.2 HRTEM images indicate schizophrenic morphology from vesicle at 26 degrees C to annular ring at 30 degrees C followed by giant size aggregation at 38 degrees C. But the reference block copolymer (PCL14-b-PDMAEMA(126), PCLD), synthesized using benzyl alcohol as ROP initiator, exhibits only core-shell morphology whose size increases with rising temperature at pH 9.2. GPCLD solution exhibits good photoluminescence (PL) property arising from GO at pH 9.2 and PL-intensity increases abruptly during phase transition. Both T-c and size of GPCLD assembly can be reversibly tuned by CO2 and N-2 gas purging. H-1 NMR spectra exhibit a gradual shift of resonance peaks of the protons on CO2 bubbling. Thus at pH 9.2 and at 38 degrees C the GPCLD acts as a good CO2 sensor. Additionally, the GPCLD vesicle can load hydrophobic guest molecules which can be released by triggering with CO2. (c) 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3878-3887