Manabu Kishimoto

13C n.m.r. studies on the microstructure of poly(vinylidene cyanide/vinyl benzoate) and poly(vinylidene cyanide/styrene)

Abstract The microstructure of vinylidene cyanide-vinyl benzoate and vinylidene cyanide-styrene copolymers, both of which were prepared by radical copolymerization, were studied by 125 MHz 13 C n.m.r. spectroscopy. The former shows high piezoelectricity, while the latter has low piezoelectricity. It was found that the compositional sequence distribution and tacticity of both copolymers were not largely different from each other, namely, both were highly alternating copolymers with a non-stereoregular structure. Possible origins of piezoelectricity were suggested for vinylidene cyanide copolymers.

Efficient Second-Harmonic Generation with a Slab Waveguide Composed of Periodically Corona-Poled Organic Copolymer

Using the slab waveguide composed of spin-coated vinylidene cyanide/vinyl acetate (VDCN/VAc) organic copolymer having the square-shaped corrugation of nonlinear optical susceptibility χ(2) with corona discharge in the guiding layer, and taking quasi-phase matching between the dominant modes of both fundamental and second-harmonic waves, enhancement of second-harmonic generation (SHG) has been demonstrated at Nd:YAG 1.06 µm and Er:YAG 2.94 µm laser lines. The SHG power with this χ(2) corrugated slab guide is theoretically evaluated, together with its enhancement factor (E.F.) to a bulk scheme. The E.F. of 500 to 800 obtained in the experiments is consistent with the theoretical estimates.

13C n.m.r. studies on the microstructure of piezoelectric copolymers of vinylidene cyanide

The microstructure of vinylidene cyanide-vinyl pivalate, vinylidene cyanide-isopropenyl acetate and vinylidene cyanide-α-methyl styrene copolymers, which were prepared by radical copolymerization, was studied by 125 MHz 13C nuclear magnetic resonance spectroscopy. The first copolymer shows high piezoelectricity. For the last two, piezoelectricity could not be measured because their films were too brittle. The copolymers were not found to differ greatly from each other: they were highly alternating copolymers with a non-stereoregular structure.

Microstructure of vinylidene cyanide copolymers with linear-chain fatty acid vinyl esters

Abstract The microstructure of vinylidene cyanide (VDCN) copolymers with linear-chain fatty acid vinyl esters, vinyl propionate, vinyl butyrate and vinyl hexanoate, was studied by 67.9 MHz 13 C n.m.r. spectroscopy. It was found that the compositional sequence distributions obtained from the analysis of the cyanide carbon (VDCN-centred) pentad and the methine carbon (comonomer-centred) triad resonances of all copolymers were highly alternative. Tactic structures in the alternating sequence were almost completely atactic. The microstructures of all copolymers were not largely different from each other. So, we suppose that possible origins of piezoelectricity observed for vinylidene cyanide copolymers should be found in other factors than the microstructure.

Anomaly in dielectric relaxation in alternating copolymers of vinylidene cyanide and fatty acid vinyl ester

Abstract Dielectric relaxation spectra at 10 Hz to 1 MHz for five vinylidene cyanide-vinyl ester copolymers were studied as functions of temperature and length of aliphatic side-chain in the comonomer unit. Three unusual phenomena in their dielectric behaviours were found: (1) extremely large dielectric relaxation strength; (2) dielectric transition phenomena whose strength changed suddenly at a critical temperature; and (3) unusual temperature dependence of the strength above the transition temperature. The dielectric transition temperature depends upon length of the side-chain and corresponds well with enthalpy peak temperature in the differential scanning calorimetry study. It was also found that the thermal history strongly affects the dielectric behaviours.

N.m.r. studies of microstructure and conformation of piezoelectric poly(vinylidene cyanide-co-vinyl formate)

Abstract The microstructure and conformation of highly piezoelectric poly(vinylidene cyanide- co -vinyl formate), prepared by radical copolymerization, were studied by 13 C and two-dimensional 1 H J -resolved n.m.r. spectroscopy, respectively. This copolymer was found to have a highly alternating and stereochemically atactic sequence and a predominantly trans -rich conformation about the main-chain methylene-methine bond in deuterated dimethyl sulfoxide solution. These structural characteristics do not differ greatly from those of other previously reported piezoelectrically active vinylidene cyanide copolymers with vinyl acetate, vinyl benzoate, and vinyl pivalate or from those of piezoelectrically less active vinylidene cyanide copolymers with styrene and methyl methacrylate.

Enhancement of SHG through slab waveguide made of organic copolymer at Er:YAG 2.94-μm laser line

Using an amorphous like VDCN/VAc copolymer a second harmonic generation (SHG) has been observed at both Nd: YAG 1.06 im and Er: YAG 2.94 μm laser lines. Here, we try to enhance the SHG power with a slab waveguide scheme under the phase-matching condition.