Crosslinking Vinyl-Addition Polynorbornenes via Difunctional Diazirines to Generate Low Dielectric-Constant and Low Dielectric-Loss Thermosets.

Thermosets having low dielectric constant (D < 3) and low dielectric dissipation factor (D < 0.003), high glass transition temperature (T > 150 °C), and good adhesion to copper are desirable for the low loss layers of the copper clad laminates (CCL) in next generation printed circuit boards. Three different difunctional diazirines are evaluated for both thermal and photochemical crosslinking of a high T vinyl-addition polynorbornene resin: poly(5-hexyl-1-norbornene) (poly(HNB)).

Model compound studies of the beta-O-4 linkage in lignin: absolute rate expressions for beta-scission of phenoxyl radical from 1-phenyl-2-phenoxyethanol-1-yl radical.

Arrhenius rate expressions were determined for beta-scission of phenoxyl radical from 1-phenyl-2-phenoxyethanol-1-yl, PhC*(OH)CH2OPh (V). Ketyl radical V was competitively trapped by thiophenol to yield PhCH(OH)CH2OPh in competition with beta-scission to yield phenoxyl radical and acetophenone. A basis rate expression for hydrogen atom abstraction by sec-phenethyl alcohol, PhC*(OH)CH3, from thiophenol, log(k(abs)/M(-1) s(-1)) = (8.

Mechanism of the Solution-Phase Reaction of Alkyl Sulfides with Atomic Hydrogen. Reduction via a 9-S-3 Radical Intermediate.

The low selectivity of benzyl alkyl sulfide fragmentation subsequent to its reaction with atomic hydrogen is indicative of a reaction that proceeds via an early transition state. The competitive reduction of a series of substituted-benzyl alkyl sulfides was insensitive to the substituent on the aromatic ring (rho = -0.13, r = 0.

Formation of Three-Membered Rings by S(H)i Displacement. Reverse of Cyclopropyl Ring Opening(1).

The general methods, photoinitiated or peroxide-initiated free radical chain additions of halomethanes to olefins, yield 1,2-addition products at temperatures ranging from 20 to 100 degrees C. At lower temperatures, -42 to -104 degrees C, a competitive reaction, subsequent to the addition of CCl(2)X(*), yields alkylcyclopropanes. The reactions of 1-octene or 1-hexene and 1-methylcyclohexene with atomic hydrogen carried out in the presence of several transfer agents (CCl(4), CCl(3)Br, CCl(2)Br(2)) initiate a radical chain addition of CCl(2)X(*) and yield cyclized materials resulting from the S(H)i displacement of halogen by a carbon-centered radical.