Abstract
Semi-interpenetrating polymer network (semi-IPN) gels have been synthesized using a hydrosilylation reaction of 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS) as a joint molecule, and a,w-nonconjugated dienes, 1,5-hexadiene (HD) or 1,9-decadiene (DD) as linker molecules in the presence of polystyrene (PS) as a liner polymers in toluene or cyclohexane. Network structure, mesh size and mesh size distribution, of the resulting semi-IPN gels was quantitatively characterized by means of a scanning microscopic light scattering (SMILS). The relaxation peaks derived from three kinds of structures were detected in the semi-IPN gels prepared in toluene by the SMILS analysis. One was derived from the mesh formed by TMCTS/a,w-nonconjugated dienes about 1-2 nm. Others were derived from transition networks about 20-150 nm and large clustered liner polymer chains about 700-2300 nm. Effect of concentration and molecular weight of the liner polymer on the network structure of the semi-IPN gels in toluene was investigated. The relaxation peaks derived from transition networks or random coils formed by aggregated PS chains were detected in the semi-IPN gels containing high concentration or high molecular weight PS. The semi-IPN gels containing PS were also prepared in cyclohexane as a poor solvent for PS at 40ºC, which was a higher temperature than the upper critical solution temperature (UCST = 34ºC) of PS in cyclohexane. The network structure of the semi-IPN gels was traced by SMILS on the cooling process. In the semi-IPN gel with the short linker molecule of HD, the relaxation peak derived from clustered PS chains was detected over the UCST. By contrast, the relaxation peak derived from transition network was observed in the semi-IPN gel with the long linker molecule of DD.
Highlights
Organic-inorganic hybrid polymers having network structures have been developed due to their characteristic properties: high transparency, high thermal stability, good mechanical strength, excellent solvent resistance, low dielectric constant, and so on
In the case of the TMCTS/HD-PS semi-interpenetrating polymer network (IPN) gel, the relaxation peaks derived from the transition network and clustered PS chains were detected in the semi-IPN gels containing low concentration of PS1 (2.5 wt%)
The TMCTS/HD or DD-PS semi-IPN gels were successfully synthesized by means of a hydrosilylation reaction using a Pt catalyst, and network structure of the semi-IPN gels was quantitatively investigated by scanning microscopic light scattering (SMILS)
Summary
Organic-inorganic hybrid polymers having network structures have been developed due to their characteristic properties: high transparency, high thermal stability, good mechanical strength, excellent solvent resistance, low dielectric constant, and so on. The authors recently attained effective synthesis of organic-inorganic hybrid gels by means of a hydrosilylation reaction of cyclic siloxane or cubic silsesquioxane with , -nonconjugated dienes. We reported co-gelation of siloxane or silsesquioxane and , -nonconjugated dienes to control the mesh size of these organic-inorganic hybrid gels precisely (Naga et al, 2007). Well-defined network structure of the present organic-inorganic gel should be useful to develop the semi-IPN gels with functionalities derived from the linear polymer. PS is soluble in kinds of organic solvents which do not poise the Pt catalyst used to synthesize the present organic-inorganic hybrid gel In this basic study, we conducted a hydrosilylation reaction of TMCTS with HD or DD in the presence of PS to form the semi-IPN gels in toluene, which is a good solvent for PS, as shown in Scheme 1.
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