Preparation and study on properties of dual responsive block copolymer-grafted polypyrrole smart Janus nanoparticles

Abstract

Polypyrrole (PPy)’s great potential applications as a conductive polymer has been restricted due to its solubility issues. Herein, in order to improve the solubility of PPy in aqueous solutions and produce dual responsive smart PPy-based nanoparticles, surface-initiated atom transfer radical polymerization (SI-ATRP) has been utilized to graft the pH and temperature responsive poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) and temperature sensitive poly(2-hydroxyethyl methacrylate) (PHEMA) on the surface of PPy nanoparticle. At first, a simple aqueous dispersion polymerization was used to prepare monodisperse and spherical PPy particles. Then, produced PPy particles were modified with a silane agent to form amine-modified PPy nanoparticles which were subsequently reacted with α-bromoisobutyryl bromide (BIBB) to form the ATRP initiator. Then, the asymmetrically modified PPy nanoparticles were utilized as initiator in SI-ATRP of DMAEMA and HEMA to form (co)polymer grafted PPy. The asymmetric modification of completely spherical PPy nanoparticles with the silane agent resulted in the formation of snowman-like and dumbbell-like Janus structures. The accuracy of the synthesis in each stage was confirmed through FTIR spectroscopy and the morphologies of resultant particles were observed via field emission scanning electron microscope (FE-SEM). The dual pH-sensitive and thermoresponsive behavior of synthesized smart particles was investigated thorough determining volume phase transition temperature (VPTT) via turbidimetry. In addition, the effect of pH, the arm length of pH-sensitive and thermoresponsive PDMAEMA block, and PHEMA second block was investigated. The results suggested both pH sensitivity and thermoresponsiveness of the produced (co)polymer-grafted PPy nanoparticles.