The principal focus of this review will be to document and discuss the recent developments in the synthesis, properties and applications of polyorganosiloxane containing block, segmented and graft copolymers and network structures. Special emphasis will be given to the synthesis and characterization of reactive, organofunctionally-terminated siloxane oligomers, which are the key starting materials or intermediates in the preparation of these well-defined copolymers. Use of these functionally terminated oligomers in the modification of network structures will be discussed. Detailed descriptions of the copolymer formation reactions and the effect of reaction variables, such as temperature and solvent, on the properties of the resultant materials will be given. Discussions of the bulk and surface morphology of siloxane containing copolymers and their blends with other polymeric systems will be provided. Potential applications of these novel materials and possible future directions in the chemistry and technology of polyorganosiloxane containing polymeric systems will also be discussed.

Polysiloxane containing copolymers: A survey of recent developments

3.1. Polysiloxane Macroinitiators 1239 3.1.1. Redox-Initiated Polymerization 1239 3.1.2. Photoinitiated Polymerization 1240 3.1.3. Ozonide Macroinitiators 1241 3.1.4. Bis-(silyl pinacolate) Macroinitiators 1241 3.1.5. Peroxycarbamate Macroinitiators 1241 3.1.6. Peroxyester Macroinitiators 1242 3.1.7. Azo Macroinitiators 1242 3.2. Polysiloxane Macromonomers 1245 3.2.1. Synthesis of Polysiloxane Macromonomers and Copolymerization 1245

Well-Architectured Poly(dimethylsiloxane)-Containing Copolymers Obtained by Radical Chemistry

This work had three objectives: to improve the reported assignments of the vibrational frequencies in several organosilicon monomers and oligomers; to assign the vibrational frequencies of polydimethylsiloxane (PDMS); and to relate the vibrational spectra of PDMS to its other physical properties, especially at sub-ambient temperatures, Infrared and Raman spectra were obtained on the title compounds, and five sets of low-temperature IR spectra were obtained on PDMS. Some low-temperature spectra were also taken on the cyclosiloxanes. Assignment of all frequencies was accomplished, although in some cases, e.g., the methyl rocking frequencies at 650-870 cm−1 and the skeletal deformations below 400 cm−1, our confidence in their correctness is less than complete. The low-temperature study showed striking changes in the IR spectrum of PDMS below its glass transition temperature Tg, Bands became sharper and in some cases showed splitting. This behavior is consistent with the concept of polymer motion being frozen below Tg, Except for the appearance of a strong, sharp band at 662 cm−1, not much change was seen in the spectrum at the "cold crystallization" point. Possibly the expected spectral changes were swamped by absorption from the more plentiful amorphous portion of the polymer matrix.

Vibrational Spectra of Me2SiCl2, Me3SiCl, Me3SiOSiMe3, (Me2SiO)3, (Me2SiO)4, (Me2SiO)x, and Their Deuterated Analogs:

Thermal properties are among the most characteristic and at the same time the most technologically important properties of polysiloxanes. They embrace a unique combination of pronounced elasticity at unusually low temperatures and high thermal and thermo-oxidative stability at elevated temperatures. These properties are characteristic of polysiloxanes because they directly originate from a specific interplay of some of the most fundamental features inherent to the basic structural building blocks that make up their repeat units, chain segments and entire macromolecules. They are therefore found in more or less all members of this family of polymers. At the same time they are also of outstanding technological importance because not only that they clearly distinguish these unique polymers from their purely organic, -C-C- type counterparts, but they often make polysiloxanes the materials of choice for many applications where performance under extreme service conditions is required and where no other polymer can successfully satisfy the purpose.

Hugh G. LeClair

Papers

On the molecular structure of methyl silicone