Multiphase polymers block copolymers

It is important to mention that the structure/properties relationships which will be discussed in the following section are valid for many polymer classes and not only for one specific macromolecule. In addition, the properties of polymers are influenced by the morphology of the liquid or solid state. For example, they can be amorphous or crystalline and the crystalline shape can be varied. Multiphase compositions like block copolymers and polymer blends exhibit very often unusual meso- and nano-morphologies. But in contrast to the synthesis of a special chemical structure, the controlled modification of the morphology is mostly much more difficult and results and rules found with one polymer are often not transferable to a second polymer. 

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-... 

Explicitly developed are models of several theoretical multiphase distributions, with corresponding depth-profile results on thin-film plasma polymers, phase-separated block copolymers, and chemical reactions on fiber surfaces. Ion impact is treated from three points of view as an analytical fingerprint tool for polymer surface analysis via secondary ion mass spectroscopy, by forming unique thin films by introducing monomers into the plasma, and as a technique to modify polymer surface chemistry. 

In the metallurgical sense, alloys are mixtures of metals with each other or with certain nonmetals, resulting in substances that may be single phase or multiphase. It should be noted that the term alloy, as referring to a macroscopically homogeneous mixture, is also used for nonmetals such as ceramics and semiconductors (e.g. Si-Ge alloys) and polymers (e.g. block copolymers) these alloys, however, are outside the scope of the present article. 

This review has illustrated various properties of multiphase polymer systems obtained from computer simulation. Three modeling techniques - atomistic, coarse-grained, and atomistic-continuum modeling - are applied to miscibility of homopolymer/copolymer and homopolymer/homopolymer blends, compat-ibilizing effect of block copolymers, and mechanical properties of semicrystalline polymers, respectively. 

SAXS results discussed hereabove show, for the first time, that the blending of mutually interacting telechelic polymers can promote a phase morphology very similar to that seen in covalently bonded block copolymers. This is a promising way to control the interfacial situation in multiphase polymeric materials. 

Until now we have considered the basic origin of birefringence and some of the general techniques used for determining this optical parameter. It is necessary, however, to discuss certain limitations when interpreting this parameter. Until now no mention has been made of two or multiphase systems such as semicrystalline polymers, amorphous block copolymers or even plasticized or filled polymers. In such systems the measured birefringence can be expressed as... 

The properties of block copolymers, on the other hand, cannot be calculated without additional information concerning the block sizes, and whether or not the different blocks aggregate into domains. The results of calculations using the methods developed in this book can be inserted as input parameters into models for the thermoelastic and transport properties of multiphase polymeric systems such as blends and block copolymers of immiscible polymers, semicrystalline polymers, and polymers containing various types of fillers. A review of the morphologies and properties of multiphase materials, and of some composite models which we have found to be useful in such applications, will be postponed to Chapter 19 and Chapter 20, where the most likely future directions for research on such materials will also be pointed out. 

The Chow equations, which constitute a large set that is too long and complex to reproduce here, are sometimes more accurate. Both of these sets of general-purpose equations (Halpin-Tsai and Chow) are applicable to many types of multiphase systems including composites, blends, immiscible block copolymers, and semicrystalline polymers. Their application to such systems requires the morphology to be described adequately and reasonable values to be available as input parameters for the relevant material properties of the individual phases. 

Colloidal and Morphological Behavior of Block and Graft Copolymers" Molau, G. E., Ed. Plenum Press New York, 1971. "Multiphase Polymers" Cooper, S. L. Estes, G. M., Eds. ADVANCES IN CHEMISTRY SERIES No. 176, American Chemical Society Washington, D.C., 1979. 

Interfacial effects on multiphase polymer systems have been of interest to polymer scientists. Apphcation of this strategy to commercially important polyolefin multiphase systems to produce tuned and/or stabilized morphologies is certainly attractive. Recently, polyolefin block copolymers have been introduced commercially and may be effective in controlling the morphology of related multiphase polyolefin systems, such as hiPP and TPO. 

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. 

Multiphase polymer blends are of major economic importance in the polymer industry. The most common examples involve the impact modification of a thermoplastic by the microdispersion of a rubber into a brittle polymer matrix. Most commercial blends consist of two polymers combined with small amounts of a third, compatibilizing polymer, typically a block or graft copolymer. 

The rheology of pol5rmer blends is discussed in detail in Chap. 7, Rheology of Pol5rmer Alloys and Blends . Here only an outline will be given. Since the flow of blends is complex, it is useful to refer to a simpler system, e.g., for miscible blends to solutions or a mixture of polymer fractions, for immiscible blends to suspensions or emulsions, and to compatibihzed blends to block copolymers (Utracki 1995 Utracki 2011). It is important to remember that the flow behavior of a multiphase system should be determined at a constant stress, not at a constant deformation rate. 

Scanning electron microscopy (SEM) is one of the very useful microscopic methods for the morphological and structural analysis of materials. Larena et al. classified nanopolymers into three groups (1) self-assembled nanostructures (lamellar, lamellar-within-spherical, lamellar-within-cylinder, lamellar-within-lamellar, cylinder within-lamellar, spherical-within-lamellar, and colloidal particles with block copolymers), (2) non-self-assembled nanostructures (dendrimers, hyperbranched polymers, polymer brushes, nanofibers, nanotubes, nanoparticles, nanospheres, nanocapsules, porous materials, and nano-objects), and (3) number of nanoscale dimensions [uD 1 nD (thin films), 2 nD (nanofibers, nanotubes, nanostructures on polymeric surfaces), and 3 nD (nanospheres, nanocapsules, dendrimers, hyperbranched polymers, self-assembled structures, porous materials, nano-objects)] [153]. Most of the polymer blends are immiscible, thermodynamically incompatible, and exhibit multiphase structures depending on the composition and viscosity ratio. They have two types of phase morphology sea-island structure (one phase are dispersed in the matrix in the form of isolated droplets, rods, or platelets) and co-continuous structure (usually formed in dual blends). 

---