Effects of Molecular Characteristics and Self-Assembled Structures on Photophysical Properties of DEH-PPV-b-PEO Block Copolymers

• Main Authors: Chien-Hsien Chang, 張建賢
• Other Authors: Shiaw-Guang Hu
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/32940112071231430435

碩士 === 國立臺灣科技大學 === 高分子系 === 96 === Data from UV-Vis spectroscopy, steady and time-resolved photoluminescence, in conjunction with Strickler-Berg equation were used to determine the photoluminescence efficiency of poly(2,5-di(2′-ethylhexyloxy)-1,4-phenylene vinyl-ene-b-(ethy- lene oxide)) (DEH-PPV-b-PEO) block copolymers. The relatio- nships between the photophysical properties and the degree of polymerization in two blocks were used to discuss the effects of molecular characteristics and self-assembled structures on pho- tophysical properities of DEH-PPV-b-PEO block copolymers. Moreover, polarized optical microscopy (POM) and thermodyn- amic analysis of micellization of polylactide-poly(ethylene glycol) block copolymers were used to investigate the effects of the degree of polymerization in PEG blocks on the order of self-assembled structures. In order to discuss the relationship between the photophysical properties and the degree of polymerization in copolymer blocks, we plot of the energy at PL emission maximum, PL quantum efficiency and radiative rate constant versus the reciprocal of the degree of polymerization in two blocks of DEH-PPV-b-PEO copolymer. As the length of the DEH-PPV increases, the energy at PL emission maximum, PL quantum efficiency and radiative rate constant all decreases. As the length of the PEO increases, the energy at PL emission maximum does not vary much, but PL quantum efficiency and radiative rate constant increases. Employing polarized optical microscopy to observe the microstructure of DEH-PPV-b-PEO at room temperature, we can find the effect of PEO segment reducing the structural order parameter, that is consistent with the results in PEG-PLLA copolymer systems. The effects of molecular chain length on photophysical prope- rties in solid-state block copolymers will be more significant than solution-state, that can be seen from plots of photophysical properities versus the reciprocal of the degree of polymerization in two blocks. Slopes in above relations relate to the self- assembled effect.