(196a) Theoretical Study of the Reaction Kinetics of Organosiloxane Polycondensation

Silicone-based polymers are commonly used in coating industry because of the interesting characteristics of organosilane molecules in forming of covalent bonding between inorganic and organic compounds. They are widely used for encapsulation and packaging of electronic

components, in medicine, and for soft lithography^1-3. The reaction mechanism involves an acid catalyzed hydrolysis followed by an SN2 type substitution. The polymerization reaction was modeled by including the two mechanisms of growth and recombination. At the early stage of the reaction, the growth mechanism is dominant as the concentrations of dimers and trimers are high. Several parameters change the reaction dynamics significantly, including the concentration of catalyst, evaporation rate and the temperature. It was found that all these factors have a direct effect on the molecular weight of polysiloxane and increase the polymer molecular weight as well as the polydispersity index. To achieve the desired molecular weight and physical properties, the tight control of the reaction is highly important.

References:

1) Schmid, H., and B. Michel. "Siloxane polymers for high-resolution, high-accuracy soft lithography." Macromolecules 33.8 (2000): 3042-3049.

2) Wong, C. P. "Thermal-mechanical enhanced high-performance silicone gels and elastomeric encapsulants in microelectronic packaging." IEEE Transactions on Components, Packaging, and Manufacturing Technology: Part A 18.2 (1995): 270-273.

3) Okoroanyanwu, Uzodinma. "Chemistry and Lithography." SPIE, 2010.