Molecular Weight Dependence of Polymer Chain Mobility within Multilayer Films

We examined the composition and molecular weight dependence of the glass transition temperature in detail for two types of hydrogen bonding miscible blends: poly (2-vinyl pyridine)/poly (vinyl phenol) (2VPy/VPh) and poly (4-vinyl pyridine)/poly (vinyl phenol) (4VPy/VPh). Regarding the functional form of the glass transition temperature, Tg, as a function of the weight fraction, we found a weak deviation from the Kwei equation for 2VPy/VPh blends. In contrast, such a deviation was not observed for the 4VPy/VPh blend. By relating the difference in the functional forms of Tg between the two blend systems to the difference in hydrogen bonding ability, we proposed a modified version of the Kwei equation. As for the interaction parameter, q in the Kwei equation, clear molecular weight dependence was observed for 2VPy/VPh blends: the lower the VPh molecular weight in the oligomer level, the higher the q values, suggesting the higher hydrogen bonding formability near the polymer chain ends than the middle part of a polymer chain.

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Polymer Chain Mobility under Shear—A Rheo-NMR Investigation

Polymers ◽

10.3390/polym10111231 ◽

2018 ◽

Vol 10 (11) ◽

pp. 1231

Author(s):

Brigitte Wiesner ◽

Benjamin Kohn ◽

Mandy Mende ◽

Ulrich Scheler

Keyword(s):

Molecular Weight ◽

Nuclear Magnetic Resonance ◽

Polymer Chain ◽

Exponential Decay ◽

High Weight ◽

Low Molecular Weight ◽

Chain Segment ◽

Chain Mobility ◽

Two Samples ◽

The Impact

The local dynamics in polymer melts and the impact of external shear in a Couette geometry have been investigated using rheological nuclear magnetic resonance (NMR). The spin-spin relaxation time, T2, which is sensitive to chain-segment motion, has been measured as a function of shear rate for two samples of poly(dimethylsiloxane). For the low-molecular-weight sample, a mono-exponential decay is observed, which becomes slightly faster with shear, indicating restrictions of the polymer chain motion. For the high-weight sample, a much faster bi-exponential decay is observed, indicative of entanglements. Both components in this decay become longer with shear. This implies that the free polymer segments between entanglements become effectively longer as a result of shear.

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Ultrasonically induced birefringence in polymer solutions

Pure and Applied Chemistry ◽

10.1351/pac200476010097 ◽

2004 ◽

Vol 76 (1) ◽

pp. 97-104 ◽

Cited By ~ 7

Author(s):

H. Nomura ◽

Tatsuro Matsuoka ◽

Shinobu Koda

Keyword(s):

Molecular Structure ◽

Molecular Weight ◽

Frequency Dependence ◽

Polymer Chain ◽

Polymer Solutions ◽

Experimental Results ◽

Segmental Motion ◽

Present Treatment ◽

Molecular Weight Dependence ◽

Ultrasonic Intensity

For ultrasonically induced birefringence in polymer solutions, both the linear sinusoidal birefringence and the nonlinear stationary birefringence were observed. The sign and value of the stationary ultrasonically induced birefringence depended on the molecular structure of segment and its anisotropy in polarizability. Furthermore, no molecular weight dependence could be observed above the molecular weight 104. The theory based on the viscoelastic ones using the Rouse-Zimm model could not explain our experimental results as a whole. These results strongly suggest that the stationary ultrasonically induced birefringence should be caused by the local segmental motion of polymer chain in solution. For all polymer solutions investigated here, the stationary birefringence per ultrasonic intensity decreased with increasing frequency. This frequency dependence is not consistent with the present treatment for the ultrasonically induced birefringence.

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