Reactive melt blending of PS-POSS hybrid nanocomposites

• Published in: Journal of applied polymer science Vol. 128; no. 1; pp. 811 - 827
• Main Authors: Bianchi, O., Barbosa, L.G., Machado, G., Canto, L. B., Mauler, R. S., Oliveira, R. V. B.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 05.04.2013; Wiley; Wiley Subscription Services, Inc
• Subjects: Applied sciences; Chain transfer; Dispersions; Exact sciences and technology; Free radicals; hybrid nanocomposite; Machinery and processing; Materials science; Melt blending; Monomers; Moulding compound preparation. Mixing; Nanocomposites; Nanostructure; Plastics; Polymer industry, paints, wood; Polymers; POSS; Styrenes; Technology of polymers; Viscoelasticity; Polymer blends; PS; Graft copolymer; Silsesquioxane polymer; Molecular structure; Silsesquioxane copolymer; Experimental study; Oligomer; Free radical reaction; Composite material; Heterogeneous mixture; Structure processing relationship; Chain transfer; Polyhedral molecule; Morphology; Reaction mechanism; Styrene polymer; POSS; hybrid nanocomposite; Rheological properties; Styrene copolymer
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.38196

Hybrid nanocomposites of polystyrene (PS) and methacryl phenyl polyhedral oligomeric silsesquioxane (POSS) were synthesized by reactive melt blending in the mixing chamber of a torque rheometer using dicumyl peroxide (DCP) as a free radical initiator and styrene monomer as a chain transfer agent. The effects of mixing intensity and composition on the molecular structure and morphology of the PS‐POSS hybrid nanocomposites were investigated. The degree of POSS hybridization (αPOSS) was found to increase with the POSS content, DCP/POSS ratio, and rotor speed. For the PS‐POSS materials processed in the absence of styrene monomer, an increase in the αPOSS led to a reduction in the molecular weight by PS chain scission, as a consequence of the free radical initiation. On the other hand, the use of styrene monomer as a chain transfer agent reduces the steric hindrance in the hybridization reaction between POSS and PS, enhancing the degree of POSS hybridization and avoiding PS degradation. The PS‐POSS morphology consists of nanoscale POSS clusters and particles and microscale crystalline POSS aggregates. PS‐POSS with higher αPOSS values and lower amounts of nonbound POSS showed improved POSS dispersion, characterized by smaller interfacial thickness (t) and greater Porod inhomogeneity lengths (lp). The processing‐molecular structure–morphology correlations analyzed in this study allow the POSS dispersion level in the PS‐POSS materials to be tuned by controlling the reactive melt blending through the choice of the processing conditions. These insights are very useful for the development of PS‐POSS materials with optimized performance. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013