Stimuli-responsive behavior of smart copolymers-grafted magnetic nanoparticles: Effect of sequence of copolymer blocks

In this work, surface-initiated atom transfer radical polymerization (SI-ATRP) is used to synthesize smart copolymer-grafted Fe3O4 magnetic nanoparticles (MNPs). To do this, MNPs is modified with (3-aminopropyl) triethoxysilane (ATPES) and alpha-bromoisobutyryl bromide (BIBB) to yield MNPs@APTES and MNPs@BIBB nanoparticles. Then, ATRP-initiator-grafted nanoparticles are used in polymerization of 2( dimethylamino) ethyl methacrylate (DMAEMA) and N-isopropylacrylamide (NIPAAm) as stimuli-responsive monomers to obtain MNPs@PDMAEMA and MNPs@PNIPAAm respectively. Homopolymer-grafted MNPs are used as macroinitiators to produce smart copolymers-grafted MNPs named MNPs@P (DMAEMA-b-NIPAAm) and MNPs@P(NIPAAm-b-DMAEMA) those have different sequences of copolymer blocks. Successful synthesis of different structures is proved by means of different methods including FTIR, TGA, VSM, XRD, FE-SEM, and TEM. All homopolymer-and copolymer-grafted MNPs are subjected to variation of pH and temperature to investigate stimuli-responsive behavior of hybrid structures. Although no surprising result is investigated for MNPs@PDMAEMA and MNPs@PNIPAAm nanoparticles, copolymer-grafted MNPs showed a dual pH- and temperature-sensitive behavior where copolymer sequence is important to define smart characteristic of hybrid MNPs. (C) 2018 Elsevier B.V. All rights reserved.