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Hybrid networks of functionalized poly(tetramethylene oxide) (PTMO) and tetraethylorthosilicate (TEOS) or titanium isopropoxide (TIOPR) were prepared through the sol-gel route. The films formed by this approach were then immersed in solutions of varying alkalinity for a period of time, removed, and dried overnight under vacuum. This treatment resulted in a better-defined two-phase microstructure in the PTMO/TEOS hybrids because of the solubility of silicon oxide in the highly basic solution. The treated hybrids exhibited higher PTMO chain mobility to the extent that the oligomeric chains could now undergo crystallization at low temperatures. The loss of silicon oxide and hydrolysis of the alkalitreated network resulted in a lower modulus than the untreated hybrid. In the PTMO/ TIOPR hybrid, due to the lower solubility of titanium oxide, the base treatment resulted in little change in the titanium oxide content but phase separation between the oligomer and the inorganic oxide was increased which also resulted in a higher mobility of the organic phase. Transmission electron microscopy data qualitatively support these proposed microstructural changes.

CP 65 d 0.221 DEP CP 86 d0 CB stands for chlorinated biphenyl and DEP for diethyl phthalate. 6 CP stands for the method using a cone-and-plate type relaxometer and TT the method utilizing the tensile tester as explained in text. c Present study. d Reference 4.

Novel elastomeric polysiloxane modifiers for epoxy networks have been synthesized and characterized. In addition, curing studies of conventional epoxy resins incorporating these oligo mers have been conducted. Structures were prepared having either epoxide, primary amine and/or secondary amine endgroups. The polymerization step for the siloxanes consisted of a base cata lyzed equilibration of the appropriately functionalized disiloxane and octamethylcyclotetrasiloxane. In the case of hydroxy piperazine terminated modifiers, polymers were first synthesized with epoxy endgroups. These endgroups were then subsequently capped with an excess of piperazine prior to curing. The oligomers were characterized by FTIR, 'H and 13C NMR, GPC, endgroup analysis and vapor pressure osmometry. The secondary amine terminated oligomers basically act as linear modifiers. By contrast, the aminopropyl functional siloxanes produce a crosslinked network. Piperazine terminated oligomers show much better compatibility with the epoxy resins compared to the aminopropyl terminated oligomers. This is especially true if the modifier contains an amide group. The curing reactions of the epoxy resins (EPON resin-828) using these oligomers and a cycloaliphatic diamine (PACM-20) were followed under a variety of conditions by DSC. Percent conversion versus time plots showed that reactivities of the functional siloxanes are higher than the cycloaliphatic amine at comparable temperatures. X-ray photoelectron spectroscopy shows the surfaces of the polysiloxane modified materials to be predominantly siloxane even at quite low bulk levels of the reactive oligomers. Preliminary mechanical property studies are encouraging and detailed morphology-property studies are continuing.