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Polymer Blend Systems (polymer + blend_system)

Distribution by Scientific Domains
Polymers and Materials Science100%

Selected Abstracts

Observation of a Charge Transfer State in Low-Bandgap Polymer/Fullerene Blend Systems by Photoluminescence and Electroluminescence Studies

ADVANCED FUNCTIONAL MATERIALS, Issue 20 2009
Yi Zhou
Abstract The presence of charge transfer states generated by the interaction between the fullerene acceptor PCBM and two alternating copolymers of fluorene with donor,acceptor,donor comonomers are reported; the generation leads to modifications in the polymer bandgap and electronic structure. In one of polymer/fullerene blends, the driving force for photocurrent generation, i.e., the gap between the lowest unoccupied molecular orbitals of the donor and acceptor, is only 0.1,eV, but photocurrent is generated. It is shown that the presence of a charge transfer state is more important than the driving force. The charge transfer states are visible through new emission peaks in the photoluminescence spectra and through electroluminescence at a forward bias. The photoluminescence can be quenched under reverse bias, and can be directly correlated to the mechanism of photocurrent generation. The excited charge transfer state is easily dissociated into free charge carriers, and is an important intermediate state through which free charge carriers are generated. [source]

Enhanced Stereocomplex Formation of Poly(L -lactic acid) and Poly(D -lactic acid) in the Presence of Stereoblock Poly(lactic acid)

MACROMOLECULAR BIOSCIENCE, Issue 6 2007
Kazuki Fukushima
Abstract Stereoblock poly(lactic acid) (sb-PLA) is incorporated into a 1:1 polymer blend system of poly(L -lactic acid) (PLLA) and poly(D -lactic acid) (PDLA) that has a high molecular weight to study its addition effect on the stereocomplex (sc) formation of PLLA and PDLA. The ternary polymer blend films are first prepared by casting polymer solutions of sb-PLA, PLLA, and PDLA with different compositions. Upon increasing the content of sb-PLA in the blend films the sc crystallization is driven to a higher degree, while the formation of homo-chiral (hc) crystals is decreased. Lowering the molecular weight of the incorporated sb-PLA effectively increases the sc formation. Consequently, it is revealed that sb-PLA can work as a compatibilizer to improve the poor sc formation in the polymer blend of PLLA and PDLA. [source]

Liquid-liquid equilibria of binary polymer blends: molecular thermodynamic approach

MACROMOLECULAR SYMPOSIA, Issue 1 2003
Bong Ho Chang
Abstract We extended and simplified the modified double-lattice model to binary polymer blend systems. The model has two model parameters, C, and C,. Those are not adjustable parameters but universal functions. In comparison with Ryu et al.'s simulation data for symmetric polymer blend with various chain lengths (r1 = r2 = 8, 20, 50, 100), C, is determined. Our results show that C, is negligible for symmetric polymer blend systems. The proposed model describes very well phase behaviors of weakly interacting polymer blend systems. [source]

Thermodynamic characterization of hybrid polymer blend systems

POLYMER ENGINEERING & SCIENCE, Issue 6 2009
Amos Ophir
A thermodynamic model was used to predict the morphology of hybrid multicomponent polymer blend systems. Two systems were studied, both including two noncompatible polymers, a third compatibilizer polymer and layered, organo-treated clays. The polar and nonpolar contributions of the surface energies of the components of the systems were calculated using measurements of the contact angles. The morphology of the multicomponent systems and the relative position of the organo-clays within them, were predicted by calculating the interaction energies between the different components of the system and evaluating these values according to the Vaia and Giannelis thermodynamic model for polymer melt intercalation in organically modified layered silicates. The experimental results show good correlation with the prediction that the organo-clays will have higher affinity to the compatibilizer polymer component situated at the interface between the two noncompatible blend components. In addition, the presence of the organo-clays in this interface was found to have a significant additional compatibilizing effect between the two polymer phases. The results presented in this work support the idea that hybrid formation via polymer melt intercalation depends mostly on energetic factors that can be determined from surface energies of polymers and organo-modified layered silicates, also in the case of multiphase polymer system. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source]