Multiphase segmented copolymers

The interfaces in multiphase segmented copolymers are diffuse. Furthermore, in the case of the purified polymer systems being studied, there is no evidence for a differentiable trapping mechanism in the interfacial regions. The frequency-dependent complex permittivity e is calculated from (26) ... 

Recently, as a further recognition of the importance of multiphase copolymers in specialty applications, siloxane containing block and segmented copolymers have received special attention for applications such as biomaterials, photoresists, gas separation membranes, protective coatings, elastomers and emulsifiers, as we shall... 

Hedrick et al. reported imide aryl ether ketone segmented block copolymers.228 The block copolymers were prepared via a two-step process. Both a bisphenol-A-based amorphous block and a semicrystalline block were prepared from a soluble and amorphous ketimine precursor. The blocks of poly(arylene ether ether ketone) oligomers with Mn range of 6000-12,000 g/mol were coreacted with 4,4,-oxydianiline (ODA) and pyromellitic dianhydride (PMDA) diethyl ester diacyl chloride in NMP in the presence of A - me thy 1 morphi 1 i nc. Clear films with high moduli by solution casting and followed by curing were obtained. Multiphase morphologies were observed in both cases. 

In general, block copolymers are heterogeneous (multiphase) polymer systems, because the different blocks from which they are built are incompatible with each other, as for example, in diene/styrene-block copolymers. This incompatibility, however, does not lead to a complete phase separation because the polystyrene segments can aggregate with each other to form hard domains that hold the polydiene segments together. As a result, block copolymers often combine the properties of the relevant homopolymers. This holds in particular for block copolymers of two monomers A and B. 

In segmented polyurethanes as well as in many other block copolymers incompatible polymer segments are combined. This incompatibility of different CRUs means that block copolymers often form multiphase systems (see TEM-... 

Here n is the average refractive index, k is Boltzman s constant, and T is absolute temperature (13). If a polyblend were to form a homogeneous network, the stress would be distributed equally between network chains of different composition. Assuming that the size of the statistical segments of the component polymers remains unaffected by the mixing process, the stress-optical coefficient would simply be additive by composition. Since the stress-optical coefficient of butadiene-styrene copolymers, at constant vinyl content, is a linear function of composition (Figure 9), a homogeneous blend of such polymers would be expected to exhibit the same stress-optical coefficient as a copolymer of the same styrene content. Actually, all blends examined show an elevation of Ka which increases with the breadth of the composition distribution (Table III). Such an elevation can be justified if the blends have a two- or multiphase domain structure in which the phases differ in modulus. If we consider the domains to be coupled either in series or in parallel (the true situation will be intermediate), then it is easily shown that... 

Segmented polyimide-polydimethylsiloxane copolymers have been successfully synthesized both in laboratory and industrial quantities to produce multiphase siloxane-modified polyimides. The siloxane detracts somewhat from the otherwise excellent thermo oxidative stability of the polyimide, but it does produce a number of important properties. These include multiphase behavior, improved adhesion to many substrates, improvements in fire resistance and enhanced gas and liquid separation membranes, where one wishes not only to maximize the contribution of the siloxane to permeability, but also to utilize the imide to re-... 

Compatibilisers are intentional additives, incorporated into multi-component, multiphase polymer systems. They are usually block copolymers, whose segments are soluble in different components of the mixture. Compatibilisers can be reactive (if they form bonds with one of the polymers in the mixture) with reactive groups like acrylic or methacrylic, maleic anhydride, or glycidyl methacrylate), or non-reactive. The main classes of compatibilisers are (a) modified PE and polypropylene-styrene containing polymers, (b) macromonomers, (c) silane-modified materials. 

For the copolymer B, Eq. (35b) is valid for all species identified by segment number rB and chemical composition Yb and considered to be continuously distributed within the total domains of these variables. Multiphase equilibria, though not considered here, may be treated analogously by extending Eqs. (35) to more phases and calculating the properties of more than one unknown phase by additional equations of the type developed below for the equiUbrium of two phases. In many cases, multiphase equilibria are obtained as multiple solutions of Eqs. (35). 

Finer morphology and higher adhesion of the blend lead to improved mechanical properties. The morphology of the resulting two-phase (multiphase) material, and consequently its properties, depend on a number of factors, such as copolymer architecture (type, number, and molecular parameters of segments), blend composition, blending conditions, and the like (25,38,39). Creton and co-workers... 

We assumed polypeptide microdomains would be formed in the matrix from vinyl polymer chains on the electrode (Figure 1), since multiphase materials including block and graft copolymers have been known in general to form microdomain structures in the solid state (72). In fact, some of those containing polypeptide segments were found to have microdomains composed of polypeptide (72-/<. In the present case, the segments from polypeptide was considered to form hydrophilic microdomains after hydrolysis. 

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