Morphology of Model A/B/(C-block-D) Ternary Blends and Compatibilization of Two Immiscible Homopolymers A and B with a C-block-D Copolymer

Abstract

The morphology of A/B/(C-block-D) ternary blends was investigated by transmission electron microscopy (TEM), and its implications in the compatibilization of two immiscible homopolymers A and B with a C-block-D copolymer are discussed. Emphasis is placed on the thermodynamic requirements and the role of order-disorder transition temperature (T ODT) of block copolymer for compatibilization. For the investigation, the following model ternary blends were prepared: (i) 63/27/10 PS/PB/(PRMSblock-PI) with PS denoting polystyrene, PB denoting polybutadiene, PRMS denoting poly(R-methylstyrene), and PI denoting polyisoprene; (ii) 63/27/10 PPO/PP/(PS-block-PEB) with PPO denoting poly(phenylene oxide), PP denoting polypropylene, and PEB denoting poly(ethylene-co-1-butene); and (iii) 63/27/10 PMMA/ PP/(PRMS-block-PI) with PMMA denoting poly(methyl methacrylate). Blend specimens were prepared by melt blending in a Mini-Max mixer at temperatures above and below the T ODT of block copolymer. The TEM images of ternary blends showed a uniform distribution of (i) PRMS-block-PI layer on the surface of PB droplets dispersed in the PS matrix and (ii) PS-block-PEB layer on the surface of PP droplets dispersed in the PPO matrix only when melt blending was carried out at a temperature above the TODT of block copolymer. The formation of a uniform interphase between two immiscible homopolymers is attributed to the attractive thermodynamic interactions existing (i) between homopolymer PB and PI block in the 63/27/10 PS/PB/(PRMS-block-PI) ternary blend and (ii) between homopolymer PPO and PS block and between homopolymer PP and PEB block in the 63/27/10 PPO/PP/(PS-block-PEB) ternary blend. The present study indicates that the T ODT of block copolymer, in relation to melt blending temperature, determines whether the block copolymer can play the role of an effective compatibilizing agent even when thermodynamic requirements (attractive interactions) for compatibilization are satisfied. Thus, we have concluded that attractive thermodynamic interactions alone are not sufficient for compatibilization of two immiscible homopolymers unless the T ODT of block copolymer is lower than melt blending temperature, because the viscosity of block copolymer in an ordered state (at T < TODT) is a few orders of magnitude higher than that in the disordered state (at T > TODT). That is, the mobility of block copolymer plays an important role in the compatibilization of two immiscible homopolymers.

Effect of homopolymer poly(vinyl acetate) on compatibility and mechanical properties of poly(propylene carbonate)/poly(lactic acid) blends

“…Although PPC and PLA have been reported to be partially compatible, compatibilization is also required to further improve its phase morphology and then endow the blend with desirable properties [18]. The introduction of well-defined block or graft copolymers into immiscible polymer blends is the most popular compatibilization strategy [19,20]. Unfortunately, to the best of our knowledge, no commercially available block copolymer can be used as an effective compatibilizer for PPC/PLA blends at this time.…”

Microphase and Macrophase Separation in Multicomponent A/B/A−C Polymer Blends with Attractive and Repulsive Interactions

“…[32][33][34][35][36][37][38][39][40][41] In this article, we use an A-C diblock copolymer to organize A and B homopolymers. The C block is designed to have attractive interactions with the B homopolymer and repulsive interactions with the A homopolymer.…”

Reinforcement of adhesion and development of morphology at polymer–polymer interface via reactive compatibilization: A review

“…The most important point in designing such materials is that most polymer pairs are thermodynamically immiscible, which results in poor interfacial adhesion. Commonly, one way to improve interfacial adhesion between two immiscible polymers is the addition of a third component (often a diblock copolymer), which can connect immiscible polymer molecules through enhanced entanglement on both side of the interface [1–10]. However, it is almost impossible for all the added copolymer molecules to reach the interface during melt blending.…”