W. H. Kim

Synthesis and Properties of a Soluble Polythiophene Derivative with a Urethane Side Chain

Abstract A solution processible thiophene polymer with a hydrogen-bond-forming urethane group in the side chain, viz., poly[2-(3-thienyl)ethanol n-butoxycarbonylmethylurethane] (PURET), has been synthesized. The polymer is soluble in a wide variety of solvents such as chloroform, dimethylsulfoxide, N-methylpyrrolidone, and trifluoroacetic acid among others. Optical quality thick films are obtained by solution casting. The presence of extensive hydrogen bonding is established with the help of temperature-dependent infrared spectroscopy. NMR spectroscopic study indicates the presence of about 33% regio-isomeric defects in the polymer. The polymer forms yellow-colored solutions (λmax = 430 nm) in most of the organic solvents, while in trifluoroacetic acid the polymer is oxidized and exhibits an additional band with an absorption maximum at around 780 nm. The conductivity of the polymer is in the order of 1 S/cm.

Dispersion of X(3) in Polydiacetylene Films from Electroabsorption Spectroscopy

Abstract Electroabsorption spectroscopy was carried out on a polydiacetylene, poly{[[8-butoxy carbonyl] methyl urethanyl]} 1-(5-pyrimidyl)-octa-1, 3-diyne (poly(BPOD)) film from 470 nm to 730 nm, and on a polydiacetylene poly-(butoxy-carbonylmethyleneurethane) (poly(4-BCMU)) film from 400 nm to 700 nm. The dispersion of the imaginary part of the complex χ eff (3) ′, which is a combination of χ 1133 (3) (ω;ω,0,0) and χ 3333 (3) (ω,ω,0,0), was directly determined from experiment. The real part of χ eff (3) ′ was calculated from its imaginary part by the Kramers-Kronig relation. The complex susceptibilities χ 1133 (3) (ω;ω,0,0) and χ 3333 (3) (ω;ω,0,0) were thus obtained from χ eff (3) ′ determined at normal and tilted incidence. The results for both polydiacetylene spin coated films satisfy χ 3333 (3) ≈ 1.5χ 1133 (3) , and are significantly different from the relation χ 3333 (3) = 3χ 1133 (3) , expected for an isotropic film. It indicates that the polymer chain segments in both polydiacetylene films lie mainly on the film plane instead of an isotropic distribution. The χ (3) values for both materials are of the order of 10 −11 esu. Some enhancement of nonlinearity of poly(BPOD) over poly(4-BCMU) is observed.

Dispersions of the third-order nonlinear optical susceptibilities χ1111(3)(ω;ω,0,0) and χ2211(3)(ω;ω,0,0) of a polydiacetylene film

Abstract The dispersions of the in-plane components χ 1111 (3) ( ω ; ω ,0,0) and χ 2211 (3) ( ω ; ω ,0,0) of a spin coated polydiacetylene film (poly(4-BCMU)) were determined through electroabsorption spectroscopy with interdigital electrodes. The maximum values of real part and imaginary part of χ 1111 (3) ( ω ; ω ,0,0) are 1.69×10 −10 esu and 1.24×10 −10 esu, respectively, and the maximum values of real part and imaginary part of χ 2211 (3) ( ω ; ω ,0,0) are 6.2×10 −11 esu and 4.2×10 −11 esu, respectively. The spectra of these two components are similar, and the ratio of χ 1111 (3) ( ω ; ω ,0,0) to χ 2211 (3) ( ω ; ω ,0,0) is found to be 2.8, very close to 3, indicating an in-plane isotropy.

Design of new polydiacetylenes as self assembling second order nonlinear optical polymers

A series of diacetylenic monomers containing a polarizable aromatic substituent at one side and a flexible sidegroup with hydrogen bonding groups at the other side are reported. BPOD, 3-BPOD and NPOD are metallic red as polymerized and highly soluble in chloroform, phenol and trifluoroacetic acid. They undergo a dramatic color transition from red(h,-510 nm) to purple(h,-590 nm) upon the addition of a nonsolvent such as hexane. Films with excellent optical quality can be prepared by spin coating or casting the solutions of these polymers. These polydiacetylenes self assemble in an acentric stable polar organization without recourse to poling. Second harmonic signals are observed from the monomer crystals of these materials as well as the bulk polymers.

Self assembled asymmetrically substituted polydiacetylene as a novel second order NLO material

Summary form only given. Polymer chains of a novel asymmetric polydiacetylene, poly((8-butoxy carbonyl)methyl urethanyl) 1-(5-pyrimidyl)-octa-1,3-diyne(BPOD) self assemble in an acentric stable polar organization upon spin coating. Spontaneous alignment of the urethane moiety caused by the intramolecular hydrogen bonds between the side groups appears to be responsible for this organization. An abrupt decrease, of SH intensity at around 130/spl deg/C is found to be closely related to the breaking of noncentrosymmety in the films in conjunction with the disruption of these intramolecular hydrogen bonds. The changes observed were reversible below 130/spl deg/C but become irreversible above this temperature. Dielectric and infrared spectroscopy confirm the relaxation of the stable hydrogen bonded polar organization at higher temperatures. The invention of this self assembling second order NLO polymer also opens up numerous possibilities in molecular design for further optimization of properties.

Steady-state photoconductivity in a novel solution-cast polydiacetylene film

Abstract Steady-state photoconductivity in solution-cast thin films of a polydiacetylene, ((8-butoxy carbonyl)methyl urethanyl)-1-(5-pyrimidyl)-octa-1,3-diyne (PDA-BPOD), has been investigated as a function of light intensity, applied electric field, incident wavelength and temperature. This newly synthesized polydiacetylene is characterized by a conjugating aromatic side group which is expected to play a role in the electronic properties of the system. The results are interpreted within the framework of one-dimensional Onsager theory of geminate recombination. The photoconductivity action spectrum shows a peak at 1.9 eV and direct band-to-band transition above 2.4 eV.

Photoconduction in a polydiacetylene film

Steady state photoconductivity, optical absorption and dark conductivity measurements in thin films of polydiacetylene ((8-butoxycarbonyl)methylurethanyl)-1-(5-pyrimidyl)octa-1, 3-diyne (PDA-BPOD) are reported. Steady state photoconductivity results are discussed within the framework of the one-dimensional Onsager theory of geminate recombination. The photoconductivity action spectrum shows a peak at 1.9 eV and a direct band to band transition above 2.4 eV. The absorption spectrum at 50 K is red shifted with respect to the 300 K spectrum. Dark conductivity studies show that the dominant conduction at high fields is due to Schottky emission with a barrier of 0.65 eV.

Novel Polydiacetylenes with Chromophoric Substituents: Materials for Second and Third Order Nonlinear Optics

Abstract The objective of this investigation was to develop stable nonlinear optical (NLO) materials which possess both second and third order NLO properties. These materials were envisioned as having a polydiacetylene (PDA) backbone with a second order active NLO chromophoric substituent. The choice of a PDA backbone in this investigation was twofold. In terms of third order NLO properties, the extensive π-conjugation of the PDA backbone leads to large ultrafast third order effects. In terms of second order NLO properties, the high thermal stability and rigidity of the PDA matrix in a perfect polymeric single crystal is expected to prevent the randomization of the NLO chromophores in the noncentrosymmetric environment. This paper focuses on the synthesis, FT-Raman structural analysis, and NLO properties of the unsymmetrical diacetylene monomers, ((9-Butoxy carbonyl) methyl urethanyl)-1-(4-urethanyl-4′- nitrobiphenyl)-nona-2,4-diyne, and ((9-Butoxy carbonyl) methyl urethany1)-1-(4-urethanyl-4′-nitroazoben...

Bulk Self-Assembled Films for Photonics

Recently we have reported, significant second harmonic generation from spin coated and bulk films of a soluble polydiacetylene (PDA), namely poly{8-[[[butoxy carbonyl] methyl]urethanyl]-1-(5-pyrimidyl)-octa-l,3,-diyne}} (BPOD) without recourse to poling. Poly(BPOD) is an asymmetrically substituted PDA in which a polarizable heteroaromatic pyrimidyl group is attached as one of the side groups. In addition to reviewing the earlier results, we report a series of new soluble PDAs of the same class with further functionalization, elaborating on the already defined design principle. A second class of polymers with azo dye based NLO chromophores incorporated into the structure has been processed optically to fabricate holographic elements. Trans-cis-trans isomerization driven reorientation and macromolecular motion leads to the formation of surface relief gratings upon exposure to an interference pattern. Fabrication of optical elements based on these polymers will be elaborated.

New Developments in Second-Order Nonlinear Optical Polymeric Materials

Abstract : Second harmonic generation from the spin coated films of an asymmetrically substituted polydiacethlene, namely poly((8-butoxy cardonylmethyl urethanyl) 1-(5-pyrimidyl)-octa-1,3- diyne(BPOD) is reported for the first time. The macromolecules assemble to produce the organization responsible for SHG without recourse to poling. d33 of the spin coated film (0.19-0.31 micrometers thickness) are between 0.78-0.88 pm/V without absorption correction and 3.32-5. 57 pm/V after correction. Angular and polarization dependence study of the second harmonic response suggests that the film has in-plane isotropy as a whole and the net dipole is nearly perpendicular to the film surface. Spontaneous orientation of the polymer chains during the film formation seems to be responsible for the noncentrosymmetric alignment of the polymer. SHG from the Langmuir Blodgett films are also reported. Second harmonic generation, Polydiacetylene, Spin coated films, Langmuir Blodgett films, Nonlinear optical, Polymeric materials, Aromatic substituents, SHG, PDA.