Identification of micellar stability zones and structural inversion process of thermoresponsive polymeric micelles by dissipative particle dynamics simulations

Abstract

ABSTRACTThe stimuli-sensitive polymeric micelles have huge applications to industrial and technological level, know their behaviour under the influence of a pure stimulus, such as the temperature is an important aspect to control and amplify its application field. In this paper, we investigate the micellar stability zones together with the structural inversion process of thermoresponsive polymeric micelles formed by a diblock copolymer (poly(N-isopropylacrylamide-b-3-[N-(3-methacrylamidopropyl)-N,N-dimethyl]ammoniopropane sulphonate (PNIPA-b-PSPP)) in an aqueous environment employing dissipative particle dynamics simulations. Our outcomes show that the PNIPA-b-PSPP copolymer has the ability to form thermodynamically stable micelles with different core-shell structure (PSPP-core/PNIPA-shell and PNIPA-core/PSPP-shell) depending on the direction of the applied stimulus (low or high temperature), the duality of this micellar behaviour is controlled by temperature effect and by the double hydrophilic character that exhibit the PNIPA and PSPP polymeric segments. Four micellar stability zones and one zone where only exist free unimer chains were detected during the thermal scan. The micellar inversion process is triggered by purely temperature effect, is totally reversible and involves three main stages: (1) micellar dissociation, (2) stabilisation of free unimer chains and (3) formation of inverse micelles, all transitory and metastable stages of micellar inversion process are described and analysed in this paper.