Intermolecular interactions polymer blend phase separation

In a fundamental sense, the miscibility, adhesion, interfacial energies, and morphology developed are all thermodynamically interrelated in a complex way to the interaction forces between the polymers. Miscibility of a polymer blend containing two polymers depends on the mutual solubility of the polymeric components. The blend is termed compatible when the solubility parameter of the two components are close to each other and show a single-phase transition temperature. However, most polymer pairs tend to be immiscible due to differences in their viscoelastic properties, surface-tensions, and intermolecular interactions. According to the terminology, the polymer pairs are incompatible and show separate glass transitions. For many purposes, miscibility in polymer blends is neither required nor de-... 

Nakano et al) reported a C CP/MAS NMR study on poly(L-Alanine) (PLA)/Polyglycine (PC) blends. The comparison between the C CP/MAS spectra of the blends and those of the parent polymers discloses that upon blending, new conformations of PLA and PC are fonned, which is closely related to the presence of intermolecular hydrogen-bonding interactions. Tip measurements demonstrate that the major parts of PC and PLA in the blends, which are in 3i-helix and a-helix conformation forms respectively, are phase separated. On the other hand, the p-sheet forms of PC and PLA, which are newly formed upon blending, exhibit similar values, demonstrating that these two parts are miscible at the scale of 3-4 nm. 

It is claimed that although measurements of the lower limit are reproducible determination of the upper limit is quite a problem with errors of 2-3 nm in the calculations. Apparently above this limit solvent cast films appear to be immiscible whatever the polymer tacticity. It is suggested that changes in the donor/acceptor emissions with tacticity are simply due to an effect on the chain conformation of the probability of intermolecular interactions. As a final criticism it is shown that heating a monophase blend above the lower critical solution temperature does not actually result in a significant enough change in the donor/acceptor emission ratio to be able to detect phase separation. However, it should be pointed out that the studies of... 

We have also reported a new series of asymmetric and color-tunable PPV derivatives, including copolymers, that were developed in order to overcome the phase separation in polymer-blending systems with MEH-PPV units. In order to improve the performance of PLEDs, the bulky dimethyldode-cylsilylphenyl group was introduced into the mcfa-position of the phenyl substitutent, which inhibits the intermolecular interaction between the... 

Chapter 6 deals with theoretical and experimental developments in the physical aging of polymer blends. In particular, aging data for polymer blends are reviewed and compared to the relevant homopolymer data. The past and present phenomenological, empirical and molecular models of aging are discussed. Enthalpic, volume, and mechanical relaxation, positron annihilation lifetime spectroscopy and other spectroscopic and scattering techniques are also considered. Then, specific examples on aging of blends are presented in systems where the effects of intermolecular interactions are important Finally, complex behaviors of aging of phase separated blends are considered. 

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