Abstract
In this review, we discuss currently available studies on the synthesis and properties of MQ copolymers. The data on methods of producing hydrolytic and heterofunctional polycondensation of functional organosilanes as well as the obtaining MQ copolymers based on silicic acids and nature silicates are considered. The ratio of M and Q monomers and the production method determine the structure of MQ copolymers and, accordingly, their physicochemical characteristics. It is shown that the most successful synthetic approach is a polycondensation of organoalkoxysilanes in the medium of anhydrous acetic acid, which reduces the differences in reactivity of M and Q monomers and leads to obtaining a product with uniform composition in all fractions, with full absence of residual alkoxy-groups. The current concept of MQ copolymers is that of organo-inorganic hybrid systems with nanosized crosslinked inorganic regions limited by triorganosilyl groups and containing residual hydroxyl groups. The systems can be considered as a peculiar molecular composites consisting of separate parts that play the role of a polymer matrix, a plasticizer, and a nanosized filler.
Highlights
MQ copolymers, often called MQ resins, consisting of mono- (M) and tetra- (Q) functional siloxane units that occupy an important place among organosiloxane polymers
Hydrolysis rates, which is higher for the chloro[5] or or alkoxysilanes alkoxysilanes[10]
[10]isisthe thedifference differenceofoftheir their hydrolysis rates, which is higher for tetrafunctional monomer and the formation of homocondensation products of
Summary
MQ copolymers, often called MQ resins, consisting of mono- (M) and tetra- (Q) functional siloxane units that occupy an important place among organosiloxane polymers. The number of patent literature on these objects is very large, and we give only the most significant of them The peculiarity of these systems is a complete absence of insoluble crosslinked structures even after prolonged high-temperature condensation their average functionality is usually higher than 2.5, and they have good solubility both in organic solvents and in polydimethylsiloxanes (PDMS). This feature makes it possible to use them widely in compositions with PDMS as reinforcing additives and fillers [21,22], curing catalysts and crosslinking agents [23], additives for production of pressure sensitive adhesives [24], durable coating films, components of sealants and casting compounds, and binding components for production of a new generation of composite materials for various purposes [25,26,27].
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