Synthesis and characterization of Novel pH stimuli responsive block copolymer

It has been demonstrated that an AB di-block copolymers aggregate to form micelles in dilute solution in a selective solvent. The core of the micelle is formed by the insoluble or poorly solvated block, while the corona contains the selectively solvated block. The critical parameters which affect the solvency and, hence, govern the formation of micelles or reverse micelles are the solution pH, electrolyte concentration, temperature and block chain length. The focus of our experiments was to characterize the di-block copolymer, polypropylene-block-polymethacrylic acid (PPO-b-MAA) and its responses to changes in pH. The aqueous solution behavior of homopolymers PPO and MAA have been studied before. PPO homopolymer with a Mn of around 2000 Daltons dissolves in cold, dilute aqueous solution but becomes insoluble at 20 °C; its lower critical solution temperature (LCST) lies between 10°C and 20°C, depending on solution concentration. Similarly, we know that MAA homopolymer is a weak acid in aqueous solution. By increasing pH, MAA becomes neutralized and at high pH is soluble. With this information we are able to hypothesize the following (Fig 1)