Molecular orientation of blue luminescent rigid-flexible polymers

Polymeric films of rigid-flexible luminescent polyethers containing substituted quinquephenyl units in the main chain and films of their diluted blends in polypropylene have been uniaxially drawn at temperatures above their glass transition. Polarized micro-Raman measurements have been conducted to evaluate the molecular orientation of the drawn polymers and probe the effect of side chain length and type. The second, P2, and fourth, P4, moments of the segmental orientation distribution function determined from the analysis of Raman spectra indicate that the longer the side-chain length is, the higher the molecular orientation attained. At short side chain lengths, the presence of an oxygen link between the alkyl side chain and the aromatic segment resulted in a restricted polymer orientation. Polarized photoluminescence measurements have shown that neat photonic polyethers display low dichroic ratios despite the high orientability shown in Raman measurements. Diluted blends of photonic polyethers in polypropylene have shown commensurate high orientation moments in Raman and enhanced dichroic ratio in photoluminescence. The implication on the perspective of the studied polyethers to give materials with polarized blue light emission is evident.