Synthesis of New Organic Crosslinking Reagents Containing SiH Bonds and Curing System Thereof

Abstract

ABSTRACT:New organic crosslinking reagents 1 containing SiH bonds have been synthesized by platinum-catalyzed "Selective Hydrosilylation"(SHS) reaction of either 1,9-decadiene 2a or diallyl ether of bisphenol A 2b with 2,4,6,8-tetramethylcyclotetrasiloxane [CHiH)Si0]4 (3) (hereafter called hydrocyclotetrasiloxane) (eq I). Identification of the new crosslinking reagents 1 was well performed by 1 H NMR. The cyclic structure of the starting hydrocyclotetrasiloxane 3 was retained in the product 1 after the SHS reaction, as evidenced by 13 C NMR analysis. The storage stability of 1 was significantly influenced by the amount of Pt catalyst still remaining in it. It could get much better when a decreased amount of Pt catalyst was used for SHS reaction and benzothiazole was added. Curing system composed of la and allyloxy end-blocked poly(propylene oxide) 4a was examined. Curing ability of the system was found to be dependent on temperature, amount of the Pt catalyst employed, and the number of the SiH bond per molecule of la. Rubbery materials could be obtained in a short period of time.KEY WORDS Selective Hydrosilylation (SHS) / Pt-Catalyzed / HydroCylotetrasiloxane / NMR Analysis/ C-0 Bond Cleavage/ Storage Stability/ Curing System / Gel Time / Modulus / Gel Content Hydrosilylation reaction has been widely employed for curing ( crosslinking) of so-called addition-type polysiloxanes. Although this type of polysiloxanes has several excellent properties such as high curing rate at high temperature, good dimensional stability etc., application of this addition-type-curing technology to organic polymers or oligomers has been eventually limited (Scheme 1 ). One of the significant reasons is probably the poor compatibility of hydrogenpolysiloxanes with organic molecules, which leads to the serious problems. 1 We have thus considered to prepare various Curing system composed of a hydrogenpolysiloxane and C-C unsaturated-bond-containing oligomer.