Large‐area polymer thin films of adjustable thickness have been prepared by a continuous bar‐coating process (see Figure). The promise of this low‐cost polymeric device production technology is exemplified by the fabrication of MEH‐PPV‐based LEDs (see inside front cover).

The structural effect of polyanions on the binding type of methylene blue (1) was investigated spectrophotometrically. 1 was bound to poly(potassium styrenesulfonate) (PSS) and poly(sodium 4-vinylphenylsulfate) (SVS) in the dimeric or slightly aggregated form and t o poly(sodium vinylsulfonate) (SVF) and poly(potassium vinyl sulfate) (PVS) in the highly aggregated (polymeric) form. It was found that the flexibility of polyanions plays an important rale in the aggregation of bound 1 and that the difference between -SO j and -0SO j as binding site is not a significant factor.

SynopsisEffect of structure of potassium poly(viny1 sulfate) and its homologs on the metachromatic behavior of methylene blue was investigated spectrophotometrically. The metkhromatic behavior with addition of polyanions was followed by the changes in the molar extinction coefficient of the 664 nm band of methylene blue and in the wavelength of metachromatic band. Important factors for metachromasy were the number of anionic sites per polymer molecule, the degree of polymerization, and the flexibility of polymer chain. It was found that the amount of KC1 or urea required to destroy the metachromasy was a useful measure for estimating the binding strength of methylene blue to polyanions.

The effect of polyanions on the formation of mixed dimers of methylene blue (1) and trypaflavine (2), methylene blue (1) and phenosafranine (3), and methylene blue (1) and pyronine G (4) was investigated spectrophotometrically. The following polyanions were used: poly(potassium styrenesulfonate) (PSS), poly(potassium vinyl sulfate) (PVS), and poly(sodium acrylate) (PAA). On addition of polyanions, the formation of mixed dimers was enhanced largely. Thermodynamic parameters inferred that the enhancement of the formation of mixed dimers in the presence of polyanions resulted from an entropic factor.

Effects of the structures of polyvinylsulfate and its homologues on the aggregation of methylene blue were studied in aqueous solution. Important factors were the number of anionic site per polymer molecule and the flexibility of polymer chain.