Poly­(propylene glycol), poly­(isoprene), and poly­(dimethlyl siloxane) (PDMS) of different molecular masses M are investigated by field-cycling 1H NMR relaxometry to monitor the crossover from segmental dynamics, to Rouse and entanglement dynamics. The spin–lattice relaxation dispersions T 1(ω) obtained at different temperatures (160 K – 400 K) are converted to the susceptibility representation χ″ DD (ω) = ω/T 1(ω). Applying frequency–temperature superposition, the data are merged to provide master curves χ″ DD (ωτ s ) with τ s = τ s (T) being the segmental correlation times. Combining them with those from dielectric spectroscopy about 12 decades in time are covered. A similar M dependence of χ″ DD (ωτ s ) is observed for all polymers (t ≫ τ s ) and comparison with dielectric normal mode spectra is carried out. In the case of PDMS showing particularities at t ≈ τ s we attempt to separate intra- and intermolecular relaxation contributions. Transformation into time domain yields the dipolar correlation function C DD (t/τ s ) which covers up to six decades in amplitude and eight decades in time. Whereas glassy dynamics is observed at shortest times, the correlation function closely follows C DD (t) ∝ t –1 at intermediate times as predicted by the Rouse theory. For longer times and high M entanglement sets in yielding C DD (t) ∝ t –ε with ε (<1) being M-dependent. As for the previously studied poly­(butadiene), a highly protracted transition to full reptation is observed.

Polyisoprenes (PI) covering a wide range of molecular weights (M in g/mol) from 652 ≤ M ≤ 4.36 × 105 are investigated by dielectric spectroscopy. Normal mode (τn) and segmental (or α-) relaxation (τα) are considered. The normal mode spectra are singled out by subtracting the spectra of the segmental relaxation. This yields the full spectrum including its high-frequency cutoff. Regarding the Rouse regime (1040 < M < 9910 ≅ M c ≅ 2M e), we are able to construct a master curve which is quantitatively reproduced by the Rouse theory provided that a weak stretching (βK = 0.8) of the correlation function is introduced for each mode. In the low M limit (M < 1040) the normal mode can not any longer be clearly identified. In the entanglement regime (M > M c) the normal mode spectrum exhibits a power-law behavior ε′′ ∝ ν−γ at high frequencies with an exponent continuously changing until it saturates around M r ≅ 105, yielding γ = 0.26 ± 0.01. Moreover, the M dependence of the ratio τn/τα changes from M 4.0 at M c < M < M r to M 3.0 at M > M r. The latter exponent is that of pure tube reptation; yet, the exponent γ = 0.26 is not compatible with the reptation model. Nevertheless, both findings we take as evidence for another characteristic molecular weight, namely, M r ≅ 20M e, beyond which entanglement dynamics are fully established. Analyzing the strength of the normal mode relaxation as a function of M yields Gaussian statistics of the chains at M > 2000, i.e., well below M c. Including data from field cycling NMR, we provide master curves for both the segmental as well as the terminal relaxation time as a function of T − T g, where T g denotes the glass transition temperature.

We apply fast field cycling 1 H NMR to study segmental reorientation dynamics in melts of linear polybutadiene, polyisoprene, and polydimethylsiloxane in the high molecular weight limit. Measuring fully protonated as well as partially deuterated polymers, we show that in contrast to previous reports the relaxation behavior at low frequencies, for which polymer-specific contributions show up, is not universal but depends on the particular internuclear vectors of the 1 H spin pairs in the monomer unit. Only after extracting the polymer specific contributions from the overall susceptibility spectra by accounting for the glassy contribution, the "polymer spectra" reveal universal behavior which can be described by two power law regimes: one attributed to free Rouse dynamics and one, at lower frequencies, to entanglement effects. Yet the predictions of the tube-reptation model are not observed.

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Bayfol is a class of polymeric solid state nuclear track detector which has many applications in various radiation detection fields. It is a Makrofol polycarbonate/polyester blend. Samples from Bayfol film have been irradiated with different fluences (1011-1014 p/cm2) of 1 MeV protons at the University of Surrey Ion Beam Center, UK. The resultant effect of proton irradiation on the structural and optical properties of the Bayfol samples has been investigated using X-ray diffraction, Fourier Transform Infrared and UV spectroscopy. The optical energy gap was decreased from 4.24 to 4.03 eV with increasing the proton fluence from 1011 to 1013 p/cm2, and was accompanied by an increase in the Urbach energy from 0.79 to 1.29 eV. This could be correlated to the results obtained from XRD and FTIR spectroscopy. Further, the non-irradiated Bayfol is nearly colorless. It showed significant sensitivity to color by proton irradiation, associated with an increase in the red and yellow color components. The variation of optical and color parameters with the proton fluence indicate that the dynamic range of Bayfol UV1 7-2 is in the fluence range from 1011 to 1013 p/cm2.

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Polyvinyl alcohol/lignosulfonate (PVA/LS) composite films have been prepared using casting technique. The effect of lignosulfonate concentrations (0.001, 0.005, 0.01, 0.05, 0.1 and 0.5 wt %) on the optical and structural properties of polyvinyl alcohol (PVA) has been investigated using UV-vis spectroscopy and X-ray diffraction. The results indicate that, the addition of LS led to a more compact structure of PVA, which resulted in an increase in its refractive index and amorphous phase. This was associated with a reduction in the optical energy gap that could be attributed to the increase in disorder structural of the composites. Moreover, the transmittance of PVA/LS composite film decreased with the increase of LS doping concentrations onto the PVA matrix. The results reflect the proper dispersion of LS in the PVA matrix that causes a strong intermolecular interaction between LS and PVA suggesting strong hydrogen bond formation between the hydroxyl group in PVA chains and the outer site groups of LS. Further, the transmission of the samples in the wavelength range of 370-780 nm, as well as any color changes, was studied. The color intensity ΔE, which is the color difference between the pure PVA sample and those with different LS concentration, increases with increasing the LS content and was accompanied by an increase in the yellow and red color components. J. VINYL ADDIT. TECHNOL., 25:85-90, 2019.