Adv Polym Technol. 2017;1–10. wileyonlinelibrary.com/journal/adv | 1 © 2017 Wiley Periodicals, Inc. Received: 14 December 2016 | Accepted: 14 March 2017 DOI: 10.1002/adv.21829 RESEARCH ARTICLE Iron oxide nanoparticles decorated oleic acid for high colloidal stability Chin Wei Lai | Foo Wah Low | Mun Foong Tai | Sharifah Bee Abdul Hamid † Nanotechnology & Catalysis Research Centre (NANOCAT), Institute of Postgraduate Studies (IPS), University of Malaya, Kuala Lumpur, Malaysia Correspondence Chin Wei Lai, Nanotechnology & Catalysis Research Centre (NANOCAT), Institute of Postgraduate Studies (IPS), University of Malaya, Kuala Lumpur, Malaysia. Email: cwlai@um.edu.my Funding information Postgraduate Research Grant (PPP), Grant/Award Number: PG068-2014B and PG061-2014B; Hartalega Sdn. Bhd, Grant/ Award Number: Modification of Existing Nitrile Latex with Magnetite; Fundamental Research Grant Scheme, Grant/Award Number: FP008-2015A; Grand Challenge Grant, Grant/Award Number: GC002A- 15SBS; University Malaya Research Fund Assistance, Grant/Award Number: BK096- 2016 † Sharifah Bee Abdul Hamid: deceased. Abstract In the present study, oleic acid (OA)-decorated magnetite nanoparticles (MNPs) were synthesized via in situ co-precipitation method using ammonium hydroxide as a precipitating agent. This study aims to determine the optimum loading amount of OA for improving the MNPs colloidal stability. Based on our results obtained, it was found that the zeta potential values of MNPs increased from −29.8 to −58.1 mV after modification of MNPs with 1.2 wt.% of OA. Indeed, results obtained clearly to show that a maximum colloidal stability of MNPs in a basic medium could be significantly improved. As a result, this resultant colloidal suspension performance was approximately 7 times higher (21 days- high colloidal stability against precipita- tion and agglomeration) than that of the undecorated MNPs sample (3 days). Based on vibrating sample magnetometer (VSM) analysis, the resultant OA-decorated MNPs exhibited superparamagnetic behavior with slightly lower saturation magneti- zation (51–69 emu/g) than that of undecorated MNPs sample (80 emu/g) at room temperature. This behavior was attributed to the sufficient carboxylate ions from the outer layer of the bilayer of OA-decorated MNPs, which promoted the high colloidal stability performance. KEYWORDS colloidal stability, magnetite nanoparticles, oleic acid, superparamagnetic 1 | INTRODUCTION Nowadays, oleic acid (OA) or oleate appeared as a promising surfactant in magnetite nanoparticles (MNPs) stabilization studies. In order to further improve the dispersion stability of MNPs in aqueous media, a facile strategy to modify the MNPs surface by decorating an optimum content of OA using in situ co-precipitation method has been introduced. This modification of MNPs surface provides sufficient re- pulsive interactions to prevent precipitation and agglomer- ation issues, which is balancing the magnetic and the van der Waals attractive forces acting on the nanoparticles. In addition, shell protection using OA is not only able to stabi- lize the magnetic properties of MNPs but it also can be used as a protection layer for MNPs against oxidation by oxygen molecules or erosion by acid or base. In this manner, MNPs stabilization with strong chemical bond between the car- boxylic acid and MNPs can be achieved. [1,2] Meanwhile, the magnetic response of MNPs had played an important role in magnetic field to manipulate the MNPs via in situ method or in controlled manner. Therefore, stable MNPs suspension can be easily blended together with others latex compounding in- gredients in producing the magnetic composite latex films with favorable magnetic properties and high comprehensive mechanical properties. [3] Recently, Mahdavi and co-researchers reported that modified MNPs surface by loading an optimum amount of OA could further improve their colloidal stability via con- trollable particle size and particle aggregation matter. [3] However, the size-dispersivity control, tendency to isolate magnetic nanostructures for aggregating into bigger clus- ter, driven by particle-particle interaction and reduction of