Copolymer multiphase

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... 

In this section of our review, recent developments in the synthesis of organosiloxane containing multiphase copolymers and networks will be discussed. Basic structural and physical characteristics of the copolymers (e.g. spectroscopic, thermal, molecular weight, etc.), supporting the formation of the multiphase structures will be given. Mechanical and morphological characteristics of representative systems will be discussed in Chapt. 4. 

Resultant multiphase copolymers displayed properties ranging from soluble thermoplastic elastomers and engineering polymers to intractable thermosets, depending on the backbone composition and orientation, and especially the level of ODA incorpora-... 

Development of several new siloxane-imide copolymers for commercial applications have also been reported by Lee 181) and Berger58). Although no information was given in terms of the chemical compositions of these materials, most of these polymers were reported to be processable by solution or melt processing techniques, most probably due to their high siloxane contents. However, due to the presence of low (—20 to —120 °C) and high (>230 °C) temperature Tg s, it was clear that multiphase copolymers have been synthesized. Molecular weights and thermal stabilities, etc, were not reported. 

Synthesis of hydrolytically stable siloxane-urethanes by the melt reaction of organo-hydroxy terminated siloxane oligomers with various diisocyanates have been reported i97,i98) -yhg polymers obtained by this route are reported to be soluble in cresol and displayed rubber-like properties. However the molecular weights obtained were not very high. A later report56) described the use of hydroxybutyl terminated disiloxanes in the synthesis of poly(urethane-siloxanes). No data on the characterization of the copolymers have been given. However, from our independent kinetic and synthetic studies on the same system 199), unfortunately, it is clear that these types of materials do not result in well defined multiphase copolymers. The use of low molecular weight hydroxypropyl-terminated siloxanes in the synthesis of siloxane-urethane type structures has also been reported 198). 

In this section of our review, we shall discuss the morphological aspects and structure-property relationships of a few specific copolymeric systems which we think will represent the general features of siloxane containing multiphase copolymers. More detailed discussions about the properties of each copolymer system may be found in the references cited during our review of the copolymer preparation methods. On the other hand an in-depth discussion of the interesting surface morphology and the resultant surface properties of the siloxane containing copolymers and blends will be provided. 

Multiphase copolymers, Ziegler-Natta catalysts for, 26 535, 537-540 Multiphase laminar flow patterning, in microfluidics, 26 961 Multiphase reactions, in microbial transformations, 16 412-414 Multi-phase reactors, 21 333-335 Multiphoton effects, in photochemical technology, 19 109... 

Note 5 The use of the term "polymer alloy for polymer blend is discouraged, as the former term includes multiphase copolymers but excludes incompatible polymer blends (see Definition 1.3). 

Polymeric material, exhibiting macroscopically uniform physical properties throughout its whole volume, that comprises a compatible polymer blend, a miscible polymer blend, or a multiphase copolymer. 

X HE IMPORTANCE AND UTILITY of multiphase copolymer systems have been well documented in the literature (1-4), with emphasis on their unique combination of properties and their potential material applications. Or-ganosiloxane block polymers are a particularly interesting type of multiphase copolymer system because of the unusual characteristics of poly siloxanes, such as their stability to heat and UV radiation, low glass transition temperature, high gas permeability, and low surface energy (i, 2, 5). The incorporation of polysiloxanes into various engineering polymers offers an opportunity for many improvements, such as lower temperatures for the ductile-to-brittle transitions and improved impact strength. 

The use of supercritical-fluid-extraction techniques in the fractionation of polysiloxanes has been demonstrated by the data presented. The poly-dispersities of the fractions were comparable with those generally attainable only by anionic-polymerization techniques, with which the incorporation of two functional groups is often difficult to attain. The ability to isolate these well-defined fractions will lead to important fundamental studies on structure-property relationships in multiphase copolymer systems. 

Sometimes, in analogous to metal alloys, the term polymer alloy is used. According to the lUPAC recommendation, the term polymer alloy for a polymer blend is discouraged. The term polymer alloy should be used for polymeric materials with macroscopically uniform physical properties in their whole volume. This definition includes compatible polymer blends, miscible polymer blends, or multiphase copolymers. 

Gas Chromatography. The retention volume of a volatile material on a gas chromatography column is determined by the interaction of the sample with the liquid phase of the column. If the column material is a polymer then a study of the elution behaviour of simple molecules provides information about the physical state of the polymer and about its interactions with the probe molecule. This inverse g.l.c. technique has been much studied and reviewed. The use of inverse g.l.c. to determine crystallinity is based on the insolubility of probe molecules in the crystal phase of a polymer and Braun and Guillet, have discussed sources of error due to non-ideality of solution of the probe molecule. Schneider and Calugaru have used inverse g.l.c. to study phase transitions in polyfethylene terephthalate) and Deshpande and Tyagi report similar studies on polyfvinyl acetate). In recent years there has been some interest in multiphase copolymer systems. Ito et report work on styrene-THF copolymers and Dincer and... 

---