Naoto Tsutsumi | PubMed Health

PubMed2006

Tunable distributed feedback lasing with a threshold in the nanojoule range in an organic guest-host polymeric waveguide.

Tunable distributed feedback lasing was achieved in a guest-host polymeric waveguide using holographic dynamic gratings. Tris(8-quinolinolato)aluminum (Alq) as a host and 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) as a guest emitter were dispersed in poly(N-vinyl carbazole) (PVCz) matrix. Emission of both the TE(0) and the TM(0) modes was measured. Effective energy transfer from PVCz to DCM through Alq assisted in the reduction of the threshold of laser emission. The threshold of 38 nJ/pulse was measured for first-order lasing and that of 53 nJ/pulse for second-order lasing.

Journal Article↗

PubMed2006

Biodegradable network elastomeric polyesters from multifunctional aliphatic carboxylic acids and poly(epsilon-caprolactone) diols.

Biodegradable elastomeric network polyesters were prepared from multifunctional aliphatic carboxylic acids such as tricarballylic acid (Yt) or meso-1,2,3,4-butanetetracarboxylic acid (Xb) and poly(epsilon-caprolactone) (PCL) diols with molecular weights of 530, 1,250 and 2,000 g.mol-1. Prepolymers prepared by a melt polycondensation were cast from DMF solution and postpolymerized at 280 degrees C for various periods of times to form a network. The resultant films were transparent, flexible and insoluble in organic solvents. The network polyesters obtained were characterized by IR absorption spectra, WAXS, density measurement, DSC, and tensile test. YtPCL1250, and XbPCL1250 network polyester films showed good elastomeric properties with high ultimate elongation (540-590%), and low Young's modulus (2.5-3.3 MPa). The enzymatic degradation was estimated by the weight loss of network films in a buffer solution with Rhizopus delemar lipase at 37 degrees C. The degree and rate of degradation were significantly affected by the molecular weight of PCL diol, chemical structures of multifunctional aliphatic carboxylic acids and the morphology of network films. The changes in the solid states of network films during the degradation were also estimated by the results of DSC and WAXS. [see text]

Biocompatible Materials↗