To combine the properties of degradability and low critical solution temperature transition in a single macromolecule, a new thermoresponsive polyester with oligo (ethylene glycol) side chains was designed. This particular polymer P (ME2MO-alt-SA) was prepared by alternating ring-opening copolymerization of functionalized epoxide [2-((2-(2-methoxyethoxy)ethoxy)methyl) oxirane, ME2MO] and succinic anhydride (SA) in bulk using metallic alkoxide as initiator. The effects of various kinetics conditions on ME2MO–SA copolymerization, such as initiator, polymerization time, temperature, monomer/initiator ratio, and feed ratio, are discussed in detail. The formation of an alternative structure is demonstrated and the conditions for ME2MO–SA copolymerization are optimized: aluminum isopropoxide (AIP) as initiator; monomer/initiator molar ratio (M/I) at 150; the feed ratio of comonomers at 0.5; polymerization temperature at 120 °C more than 12 h. From the NMR spectra, the initiation end group is confirmed to be isopropanol ester that results from the initiation reaction of AIP with SA. However, the termination end group was variable and could be hydroxyl, carboxyl or their mixture, depending on the feed ratio of ME2MO/SA. Based on the above experimental results, the possible coordination–insertion mechanism was proposed for alternating ring-opening copolymerization of ME2MO and SA initiated by AIP, which suggested the two monomers are inserted into the O–Al and COO–Al active ends alternately.