350 ISSN 0965-545X, Polymer Science, Series A, 2018, Vol. 60, No. 3, pp. 350–358. © Pleiades Publishing, Ltd., 2018. Understanding the Miscibility and Morphology of Poly(methyl methacrylate) and Styrenic Copolymer Blends of Tunable Domain Sizes 1 Sharmila Muthukrishnan a, *, Akhilesh Tanwar a , Sharankumar G. Shetty a , Pradeep Singh a , Yogesha Subbaiah a , Arun Sikder a , Radha Kamalakaran a , and Bander Al-Farhood b a SABIC Technology Center (STC), Bangalore, Bengaluru, 562125 India b SABIC Technology Center (STC), Riyadh, 11551 Saudi Arabia *e-mail: sharmila.muthukrishnan@sabic.com Received July 7, 2017; Revised Manuscript Received November 23, 2017 Abstract—In the present study, we have investigated the miscibility, morphology and mechanical behavior of poly(methyl methacrylate) (PMMA) blends with a series of poly(styrene-co-maleic anhydride) (SMA) copo- lymers containing varying amounts of maleic anhydride (MA) content (from 8 to 26%). The experimental findings have been substantiated by the modeling studies to gain fundamental understanding of the observed phenomena with respect to the miscibility of the PMMA and SMA blends of a given MA content. The mor- phological differences, molecular weights, domain sizes and mechanical behavior of the blends at a given ratio of PMMA and copolymers have been investigated and a correlation has been made between the mor- phological understanding to the molecular weights and mechanical properties. The results indicate that the PMMA/SMA blends are miscible only at a certain MA content providing transparent PMMA/SMA blends without affecting any of the enabling properties of PMMA that are of commercial interest through a facile melt mixing process. The surface hardness and % recovery (nano-indentation) of these blends were evaluated as well to gain fundamental understanding of the surface characteristics and mechanicals of the blends. DOI: 10.1134/S0965545X18030136 INTRODUCTION A large number of commercial “Polymer alloy” products have been continuing to make inroads into various industrial materials [1]. Most of them are composed of immiscible polymer systems, where mul- tiple phase separation is an essential feature of the blend. The additive or synergistic impact of the poly- mer blends drive many important features of the blend systems. The final product characteristics depend on good adhesion between the components, miscibil- ity/compatibilization and adequate cross-linking between various components [1]. Poly(methyl methacrylate) (PMMA), an amor- phous thermoplastic consisting mainly of methyl methacrylate, has excellent transparency, ultraviolet (UV) stability, high surface hardness and scratch resis- tance. Therefore, PMMA applications are widely diverse such as optical devices for liquid crystal dis- plays (LCDs), lamps for cars, signs, lighting, architec- tures and construction. However, PMMA does not have good impact and heat resistance properties which are the key customer requirements for certain applications such as LED automotive, street, medical lighting. In such cases, the PMMA blends with other copolymers or additives are being preferred [2, 3]. Many applications demand improvement in either impact or heat resistance with- out affecting any of the enabling properties of PMMA which appears to be of greatest challenge especially in the processing range of PMMA using melt process. The phase behavior and compatibilization mecha- nism of PMMA with other polymers of interest have been studied at a greater depth [4]. Styrene/maleic anhydride copolymers (SMA) are thermoplastics that are transparent in nature with high heat resistance. The high heat properties of SMA can be imparted to PMMA when added in the desired lev- els in the miscible region without affecting any of the enabling properties of PMMA. In our study, we have investigated the miscibility, morphological behavior and mechanical properties of PMMA blends with sty- renic copolymers containing varying amounts of MA content. The range of the miscibility of PMMA and SMA blends are then validated through the modeling studies. 1 The article is published in the original. POLYMER BLENDS