Miscible polymers chemically dissimilar

A fundamental question, which has to be addressed first about any blend system of interest, is of course whether the components are miscible or not. Polymer mixtures of chemically dissimilar polymers can be divided on the basis of the miscibility of their components being miscible, partially miscible or fully immiscible. 

Chemically dissimilar polymer pairs miscible in the amorphous state at room temperature. Some of these polymers may be copolymers, but the polymer pairs may not have any monomer units in common. One or both of the polymers may be semicrystaUine. 

Chemically dissimilar polymer triads and tetrads miscible in the amorphous state... 

Table 21.1 Chemically dissimilar polymer pairs miscible in the amorphous state at room temperature... 

Krause [5] reviewed the miscible polymer pairs reported in the literature. She found that there were 282 chemically dissimilar polymer pairs that appeared to be miscible in the amorphous state at room temperature. She found that 15% of these were miscible on account of specific interactions such as hydrogen bonding 15% of the miscible pairs were due to clever choice of copolymer composition. The compositional window over which copolymers are miscible with each other can be calculated from the Flory-Huggins theory. 

According to the Nobel laureate P. Flory finding thermodynamically miscible polymers is difficult to do unless they have specific interactions with each other. Krause found 282 chemically dissimilar polymer pairs that appeared to be miscible 75% of these were miscible because of specific interactions 15% of the miscible pairs were due to clever choices of copolymer composition. Since Flory s work, a number of miscible polymer blends have been found. A patent search today on polymer blends returns 63,105 entries. In this work, compatible commercial systems and thermodynamically miscible systems are distinguished from each other. 

A theory has been developed for the viscoelasticity and diffusion of miscible fluid blends of entangled linear polymers with dissimilar chemical structure. The architecture and molecular dynamics of the... 

In this section, we present the molecular theory for the linear dynamic viscoelasticity of miscible polymer blends by Han and Kim (1989a, 1989b), which is based on the concept of the tube model presented in Chapter 4. Specifically, the reptation of two primitive chains of dissimilar chemical structures under an external potential will be considered, and the expressions for the linear viscoelastic properties of miscible polymer blends will be presented. We will first present the expressions for zero-shear viscosity ob. dynamic storage and loss moduli G co) and G " co), and steady-state compliance J° for binary miscible blends of monodisperse, entangled flexible homopolymers and then consider the effect of polydispersity. There are a few other molecular theories reported... 

There are several factors that are either not included or assumed to be unimportant in the Stockmayer-Kennedy theory. Hydrodynamic interactions between two chains in a block copolymer are not included in the theory. This can be a serious omission, especially when dealing with low-molecular-weight diblock copolymers, such as the SI diblock copolymers considered above. Intermolecular (thermodynamic) interactions between chemically dissimilar chains are also neglected. Inclusion of such interactions can be important, especially when the chemical affinity between two chemically dissimilar chains is rather poor, such as the case in the SI diblock copolymers considered here. In Chapter 7, which discusses the rheology of miscible polymer blends, we pointed out the importance of the segmental interaction parameter in the prediction of the linear... 

Table 3. Chemically Dissimilar Polymer Triads (and Tetrads) Miscible In the Amorphous State at Room Temperature VI-448...

TABU 1. CHEMICALLY DISSIMILAR POLYMER PAIRS MISCIBLE IN THE AMORPHOUS STATE AT ROOM TEMPERATURE... 

In those miscible, high polymer pairs showing no specific interaction the polymers are usually very similar chemically. Other polymers which are not similar chemically are nevertheless miscible due to specific interactions between dissimilar groups in... 

PS and PVME are a rather unique pair of polymers that are dissimilar, both chemically and in their response to irradiation, yet they form miscible blends over the entire range of composition. McHerron and Wilkes [1993] report on the effects of dose, blend composition and the state of miscibility on the gel content obtained on electron irradiation of PS/PVME blends (Table... 

Chemical shifts in the C-NMR spectra can provide evidence of specific interaction between dissimilar components of the blend. A method termed cross-polarization, magic angle spinning (CPMAS- CNMR) has shown promise in identification of the environment of carbon nuclei in blends along with an assessment of the degree of homogeneity. Xe-NMR has been employed to determine structural order in amorphous blends. Xenon as a probe molecule will show separate resonances for a phase separated blend, but singular values for miscible blends. Examples where NMR techniques have been utilized for polymer blends will be briefly noted in this section. Reviews on the use of solid-state NMR to study the miscibility and characteristics of polymer blends include [223,224]. 

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