PNIPAm-PEO-PPO-PEO-PNIPAm Pentablock Terpolymer: Synthesis and Chain Behavior in Aqueous Solution

The double thermosensitive and narrow dispersed PNIPAm110-PEO100-PPO65-PEO100-PNIPAm110 pentablock terpolymer was synthesized by the typical atomic transfer radical polymerization (ATRP) method with N-isopropylacrylamide (NIPAm) as the monomer and modified poly(ethylene oxide)100−poly(propylene oxide)65−poly(ethylene oxide)100 (PEO100-PPO65-PEO100) block copolymer as the macroinitiator. Microdifferential scanning calorimetry (micro-DSC) data showed that the pentablock terpolymer exhibited two low critical solution temperatures (LCSTs) at 31 and 34 °C in the aqueous solution, which can be attributed to the thermal phase transition of the PPO block and PNIPAm block, respectively. The chain conformation of the pentablock terpolymer in aqueous solution was then studied in detail by using a combination of static and dynamic laser light scattering (SLS-DLS). The SLS-DLS results indicated that the loose “associates” and single coil chains coexisted in the aqueous solution at the low temperature, where the PEO, P...