Sequential amphiphilic and pH responsive hyperbranched copolymer: influence of hyper branching/pendant groups on reversible self assembling from polymersomes to aggregates and usefulness in waste water treatment

Abstract

A library of layered amphiphilic hyperbranched copolymers capable of reversible self assembling from polymersomes to aggregates is developed by a combination strategy of “Strathclyde method” and click reaction. Owing to a wide difference in reactivity and polarity between the reacting monomers with respect to the reaction medium, almost a sequential and controlled “Strathclyde” polymerization happens (exhibit PDI < 1.5 but high MW). In fact, sequential polymerization creates distinct layers of hydrophilic and hydrophobic groups in the copolymers. Further functionalization at the pendant groups induces an optimum balance in hydrophilic and hydrophobic layers which develops self assembling properties in the copolymers in response to pH of the medium. A thorough examination through various experiments (DLS, zeta potential, FESEM and rheology) confirms that an optimized extent of hyper branching and presence of pendant cetyltrimethyl ammonium triazole ion pairs as well as carboxyl groups play pivotal roles in the formation and subsequent stabilization of the different macromolecular architectures of the copolymers in different ranges of medium pH. The presence of both hydrophilic and hydrophobic groups also creates layers along with an aqueous core in the copolymers at high medium pH for which both hydrophobic and hydrophilic molecules are encapsulated. However, retention of different guest molecules by the copolymers at low pH differs due to increase in hydrophobicity by polymer aggregation. In this work, the new type of hyperbranched copolymer as mentioned is unique to our knowledge and thus may appeal to many researchers in near future. In fact these hyperbranched copolymers are good promising tools for removal of organic wastes from water bodies.