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Dicumyl peroxide initiator (2wt% of polysilazane) was first dissolved into PSZ. This PSZ and PB-b-PEO were then dissolved separately in a 1:1 (vol.) mixture of tetrahydrofuran and chloroform to obtain 5wt% solutions. Subsequently the solutions of precursor and block copolymer were mixed according to the designed proportion.These homogenous solution mixtures were then cast into Teflon dishes and allowed to dry at room temperature for 6-12 hours. All mixing and drying was conducted in a glove box under nitrogen.The dried polymer blends were transferred into a vacuum oven pre-set to 70°C to eliminate any residual solvent, then annealed at 100°C for 12 hours to allow for self-assembly of PB-b-PEO and PSZ. Films of about 0.5 mm in thickness were then peeled from the Teflon dishes and transferred into a tube furnace with flowing nitrogen. The samples were heated to 400°C for one hour in order to induce cross-linking. Pyrolysis experiments were conducted by further heating the cross-linked samples at a constant rate of 0.5°-20°C/min to final temperatures of 700° to 1500°C, the dwell time at the final pyrolysis temperature was 2-4 hours.Transmission electron microscopy. Polymeric samples were microtomed either at room temperature (after being embedded in an epoxy matrix) or at -150°C. Fully pyrolyzed samples were crushed into fine particles and dispersed onto a thin holey-carbon support film. All samples

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It can be concluded that the use of antioxidant before bonding procedures on bleached enamel completely neutralizes the deleterious effects of bleaching and increases the bond strength significantly.

Mode I and Mode II strain energy release rates for a crack lying along the interface of two dissimilar orthotropic elastic solids are investigated analytically and also by the finite element method. It is shown that due to the violent oscillatory crack tip stress behavior, the strain energy release rates for Mode I and Mode II do not converge to definite values. Both GI and GII can be expressed in terms of ½G (G is the total strain energy release rate) plus oscillatory terms. However, the total strain energy release rate is well-defined.

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