Charles A. Langhoff

Perfluorocyclobutane (PFCB) polyaryl ethers: versatile coatings materials

Abstract The cyclopolymerization of aromatic trifluorovinyl ether (TFVE) monomers offers a versatile route to a unique class of linear and network fluoropolymers containing the perfluorocyclobutyl (PFCB) linkage. Polymerization proceeds by a thermal — radical mediated — step-growth mechanism and provides well-defined polymers containing known fluoroolefin end groups. PFCB polymers combine the engineering thermoplastic nature of polyaryl ethers with fluorocarbon segments and exhibit excellent processability, optical transparency, high temperature performance, and low dielectric constants. An intermediate strategy utilizing Grignard and aryllithium reagents has been developed which offers access to a wide variety of hybrid materials amenable to coatings applications. Liquid crystalline examples have recently been achieved in addition to tailoring optical properties by co-polymerization.

Third order nonlinear optical properties of group 4 metallocenes

Abstract The third order nonlinear optical (NLO) coefficients (γ) of Ti, Zr, and Hf metallocene halides, acetylides and alkenylzirconocene compounds were measured with a third harmonic generation technique with a fundamental laser frequency of 1908 nm. Metallocene halide compounds have γ of less than 5 × 10 −36 esu. Titanocene bisphenyl-acetylide has the largest γ (92×10 −36 esu) of the metallocene acetylide compounds. The γ of the metallocene acetylide complexes are significantly larger than the sum of the free organic acetylene and the metallocene halide compounds. Cp 2 Zr(Cl)CHCH-1,4-phenyl-CHCH(Cl)ZrCp 2 has the largest γ (154×10 −36 esu) of any of the group 4 metallocene compounds studied. The origin of this optical nonlinearity is most likely due to a conjugated π system, which involves the Cp-metal bonding network and like symmetry orbitals of the vinyl and acetylide ligands.

Nonlinear optical activity of bisphenol A polycarbonate and related copolymers

A series of structurally modified polycarbonates (PC) have been demonstrated to have second-order nonlinear optical (NLO) activity. The dipolar functionality and NLO activity in these polymers are properties of the polymer backbone. d33 values of 0.08-1.35 x 1O esu were determined by second-harmonic generation (SHG) measurements using a Maker Fringe rotation approach. In-situ measurements of the NLO activity as a function of temperature during the parallel plate poling process show that the onset of the NLO activity occurs primarily near the polymer glass transition temperature. A study of the temporal stability of the NLO activity shows persistent NLO activity for at least 640 days after poling. An effective j per polymer repeat unit is calculated from the data and compared to PPP semi-empirical calculations ofj for model molecules. Agreement is shown to be best for carbonate-containing models of the polymer backbone. The approximate agreement of theory and experiment suggests that the orientability of the NLO active segments in the polymer backbone is adequately described by poling theory.

Nonlinear optical properties of inorganic coordination polymers and organometallic complexes

The synthesis and characterization of a new class of dipolar inorganic coordination polymers, as well as the examination of the third-order NLO properties of several organometallic acetylide complexes, are discussed. The dipolar materials were prepared for Cr, Mn, and Fe. The crystal structure of two Mn complexes demonstrate that coordination polymers are being formed in the solid-state. Solution third harmonic generation (1907 yields 636 nm) was used to determine the molecular hyperpolarizibilities ((gamma) ) for several organometallic halide and acetylide complexes. The values of (gamma) range from <3 X 10-36 to 50 X 10-36 esu.