Poly($D,L$-lactide-$co$-glycolide)-$b$-poly(ethylene glycol)-$b$-poly($D,L$-lactide-$co$-glycolide) (PLGA-PEG-PLGA) triblock copolymers were synthesized at 130 and $160^{circ}C$. The concentrated aqueous solutions of both specimens underwent reversible sol-to-(transparent gel)-to-(opaque gel) transitions upon heating but exhibited different critical gelation concentrations and transition temperatures, possibly due to the minor sequence differences between $D,L$-lactide (LA) and glycolide (GA) in the PLGA blocks. Aqueous solutions (20 wt%) of the copolymers synthesized at 130 and $160^{circ}C$ spontaneously formed an opaque gel and a transparent gel at body temperature, respectively. The resulting hydrogels displayed similar $in$ $vitro$ degradation profiles in phosphate buffer saline solutions at $37^{circ}C$. Nevertheless, the late-stage releases of bovine serum albumin from the physical hydrogels differed. The present study reveals for the first time that transparent $vs.$ opaque thermogel state influences some of their biomaterial-related properties $via$ the "overheat degree" of the thermogelling systems at a given working temperature, usually $37^{circ}C$.