Poly-3-butoxycarbonylmethylurethane (poly-3BCMU) spun films were formed from polymer batches with different molecular weight (from about 100,000 to 375,000 g/mol). The two-photon absorption (TPA) spectrum of poly-3BCMU films was measured in the near infrared from 800 to 1350 nm by using femtosecond pulses. Although the TPA spectrum features were the same in all investigated films, the TPA coefficient β was two times larger in the films obtained from the higher molecular weight batches. As the number of repeat units in all polymer batches was well above the saturation limit of the hyperpolarisability γ in conjugated chains, the observed behaviour can be explained with the assumption that a more ordered and planar arrangement of the polymer chains is promoted in the polymer films with higher molecular weight. This hypothesis is confirmed by the measurement of the film refractive index and birefringence.
Molecular Weight Induced Order in poly-3BCMU spun films
GRANDO, DANIELA;BANFI, GIAN PIERO;
2003-01-01
Abstract
Poly-3-butoxycarbonylmethylurethane (poly-3BCMU) spun films were formed from polymer batches with different molecular weight (from about 100,000 to 375,000 g/mol). The two-photon absorption (TPA) spectrum of poly-3BCMU films was measured in the near infrared from 800 to 1350 nm by using femtosecond pulses. Although the TPA spectrum features were the same in all investigated films, the TPA coefficient β was two times larger in the films obtained from the higher molecular weight batches. As the number of repeat units in all polymer batches was well above the saturation limit of the hyperpolarisability γ in conjugated chains, the observed behaviour can be explained with the assumption that a more ordered and planar arrangement of the polymer chains is promoted in the polymer films with higher molecular weight. This hypothesis is confirmed by the measurement of the film refractive index and birefringence.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
