Abstract
To overcome the inherent limitation that the preparation of high molecular weight MQ copolymers (Mw ≥ 30,000 g/mol) via the hydrolysis and condensation of solicate salts generally results in an intractable gel, vinylphenyl-containing MQ silicone resin with a high molecular weight was designed and synthesized through the hydrosilylation reaction of vinyl-containing MQ silicone resin and linear poly(diphenylsiloxane) with two terminal Si–H bonds. The weight average molecular weight of these modified copolymers reported here is at least 30,000 dal·mol−1. These polymers have favorable thermal stability and a higher refractive index than that of the base resin due to the formation of novel regular macromolecular structures and the introduction of phenyl groups. These inorganic/organic hybrid materials could be used as a potential component for temperature-resistance electronics adhesive, heat-resistant coatings and high-performance liquid silicone rubber. Moreover, the proposed process also provides a possibility to choose higher molecular weight MQ silicones according to application requirements.
Highlights
MQ-type silicone resins are polymers consisting of mono-functional siloxane (R3 SiO1/2, the M units) and tetra-functional siloxane (SiO4/2, the Q units) [1,2], wherein R is a functional or nonfunctional organic group, such as hydrogen, vinyl, methyl, aryl and some related organic or inorganic groups.These are called hydrogen-containing MQ silicone resin, vinyl-containing MQ silicone resin, methyl-containing MQ silicone resin and so on.Since it was first synthesized by Herbert and his co-workers in the early 1950s [3], MQ-type silicone resins have attracted great attention in commercial applications owing to their special structures and properties
MQ silicone resin is an essential part of silicone hot melt adhesive [9], as it can effectively improve the mechanical and adhesive properties
The molecular weight of MQ silicone resin is mainly determined by the molar ratio of M units to
Summary
Since it was first synthesized by Herbert and his co-workers in the early 1950s [3], MQ-type silicone resins have attracted great attention in commercial applications owing to their special structures and properties They are used as a tackifier for silicone pressure-sensitive adhesives [4], as silicone hot melt adhesive additives [5], as the reinforced fillers of liquid silicone rubber [6], as the reinforced agent for heat-resistant coatings [7], etc. Using an MQ resin with an exorbitant molecular weight as a tackifier for silicone pressure-sensitive adhesive will lead to the decrease of the initial adhesion of the adhesive This does not influence the importance of this polymer, because it can be possible to choose higher molecular weight MQ silicones according to application requirements
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