Birefringence and dichroism of poly(vinyl-alcohol) foils containing phthalazinium ylids

Pure and colored with phthalazinium ylids poly(vinyl-alcohol) (PVA) foils were stretched under gentile heating. The birefringence of the thin foils was determined with a Babinet compensator standardized for yellow radiation of a Sodium lamp. The determined birefringence of the colored PVA foils is higher than that of the pure PVA foils. This fact indicates that the phthalazinium ylids facilitate the increase in the anisotropy of the stretched foils. The visible absorption electronic band of phthalazinium ylids was used to estimate the dichroic ratio and the degree of order of the ylid molecules in the stretched PVA foils. An increase in dichroism and birefringence with the degree of stretching has been evidenced for uncolored and colored PVA foils.

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• Birefringence of colored and uncolored PVA foils increases with stretching degree.
• Colored PVA foils show linear dichroism.
• Dichroism increases by stretching degree.
• Phthalazinium ylids improve the polymer chains alignment by dipolar interactions.
• The degree of order of the colored molecules can be estimated by dichroic ratio.