Molecular weight effect on the miscibility of poly(ethylene oxide) and isotactic poly(methyl methacrylate) in their blends

Manipulation of Fracture Behavior of Poly(methyl methacrylate) Nanocomposites by Interfacial Design of a Metal-Organic-Framework Nanoparticle Toughener

The interfacial region between nanoparticles and polymer matrix plays a critical role in influencing the mechanical behavior of polymer nanocomposites. In this work, a set of model systems based on poly(methyl methacrylate) (PMMA) matrix containing poly(alkyl glycidyl ether) brushes grafted on 50 nm metal-organic-framework (MOF) nanoparticles were synthesized and investigated. By systematically increasing the polymer brush length and graft density on the MOF nanoparticles, the fracture behavior of PMMA/MOF nanocomposite changes from forming only a few large crazes to generating massive crazing and to undergoing shear banding, which results in significant improvement in fracture toughness. The implication of the present finding for the interfacial design of the nanoparticles for the development of high-performance, multifunctional polymer nanocomposites is discussed.

Size effects on miscibility and glass transition temperature of binary polymer blend films

After determining the size dependent miscibility of binary polymer blend films using molecular dynamics simulation and thermodynamics, the size dependent glass transition temperatures Tg(w,D) of several polymer blend films in miscible ranges are determined by computer simulation and the Fox equation where w is the weight fraction of the second component and D denotes thickness of films. The Tg(w,D) function of a thin film can decrease or increase as D decreases depending on their surface or interface states. The computer simulation results are consistent with available experimental results and theoretical results for polymer blend films of PPO/PS [poly(2,6-dimethyl-1,4-phenylene oxide)/polystyrene] and stereoregular PMMA/PEO [poly(methyl methacrylate)/poly(ethylene oxide)]. The physical background of the above results is related to the root of mean square displacement of thin films in their different regions.