Rheo-optical studies

Studies of deformation-induced changes in polymers by vibrational spectroscopic techniques can lead to a better understanding of structure-property relationships. They may provide insights into the micros true tural mechanisms of orientation, relaxation and conformational rearrangement. 

A rheo-optical measurement is considered to be a combination of a mechanical test with a simultaneous optical measurement. In rheo-optical FTIR 

The potential of ROFTIR has been exploited in a wide variety of polymer systems. These include the orientation processes during elongation and relaxation of polyethylene [299-301, 312] uniaxial deformation phenomena in polypropylene [302, 303, 309-311], PET [304, 305] and polystyrene [306] hard and soft segmental orientations during stretching of polyurethanes [307, 308] and the stress-induced reversible a-P phase transition in crystalline PBT [312-314] and uniaxial deformation of amorphous PBT [315]. 

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Since the tack and green strength of these rubbers may depend on their ability to undergo strain induced crystallization, this behavior was studied and compared with that shown by NR. Information on the strain induced crystallization behavior of these experimental rubbers was obtained from x-ray diffraction measurements and from rheo-optical studies. 

Rheo-optical Studies. One of the most useful techniques for studying the crystallization behavior of stereoregular polymers is rheo-optical measurements (11). 

Siesler, H. W. Polymer Deformation A Rheo-Optical Study by Fourier Transform Infrared Spectroscopy, preprint... 

T. Asada, H. Muramatsu, R. Watanabe, and S. Onogi, Rheo-optical studies of racemic poly (y -benzyl glutamate) liquid crystals, Macromolecules, 13,867... 

P. L. Frattini and G. G. Fuller, Rheo-optical studies of the effect of weak Brownian rotations in sheared suspensions, J. Fluid Mech., 168,119 (1986). 

The initial cholesteric structure present, especially m dioxane, is considered to be separated into small fragments upon putting the solution between the cone and the plate of the rheogoniometer, and it appears unthinkable that the continuous cholesteric structure is kept during the rotation of the plate. Rheo-optical studies on the liquid crystalline solution have just started (52), and will supply extra information about the solution structure under shearing stresses. 

Onogi, S., Asada, T. Rheo-optical studies of high polymers IX. J. Polymer Sci. C, 1445 (1967). 

An area that will require attention in the future involves in-line analysis of polymer blends during processing potentially allowing feedback information to improve uniformity of the resultant blend. In-line morphology determination, rheological measurements, and shear-induced phase behavior are subjects for consideration. Rheo-optical studies under shear for low molecular weight PS/PIB blends near phase separation conditions were... 

Rheo-Optical Studies on the Structural Re-Format ion of Nematic Liquid Crystals of Rod-Like Polymers After Cessation of Steady Flow. 399... 

RHEO-OPTICAL STUDIES ON THE STRUCTURAL RE-FORMATION OF NEMATIC LIQUID CRYSTALS OF ROD-LIKE POLYMERS AFTER CESSATION OF STEADY FLOW... 

This section deals with thermotropic PLCs. The story starts, however, with lyotropic PLCs for which the long structural relaxation times of PLCs, compared to those of conventional flexible chain polymers, were first realized from rheo-optical studies [118]. Figure 10.12 presents the fundamentals of the important early discovery a specimen first oriented by shear flow which is suddenly switched off exhibits a rapid stress relaxation within a period of seconds. The decay of birefringence is however slower and it takes a very significant period of time. 

Wu, R., Shaw, M.T., and Weiss, R.A. (1992) Rheo-optical studies of stress-induced phase changes in blends exhibiting UCST polystyrene and polyisobutylene. J. Sheol., 36 (8), 1605-1623. 

G. Kiss and R.S. Porter, "Rheo-optical Studies of Liquid Crystalline Solutions of Helical Polypeptides," Mol. Cryst. Liq. Cryst., 60, 267-280 (1980). 

The film samples utilized for the rheo-optical studies were prepared from PTMT chips by hot pressing at 523 K and quenching in ice water. Sections of this sample were drawn in hot water to a draw ratio of = 4 and finally annealed at constant length under vacuum at 483 K for 15 hours. The density of such samples was 1.328 g cm and the film strips were cut 20 mm in length and 5 mm in width and had a thickness of af roximately 0.025 mm. 

Kiss and Porter [7] observed the transverse striations in a rheo-optical study of sheared solutions of PBLG of about 14 wt % /n-cresol. They indicated that molecules within the striae are oriented at 45° to the direction of shear and suggested that the striae form planes about 10-30 /u.m in width that traverse the entire sample volume. They postulated that adjacent striae do not coalesce because molecules within them are perpendicular to each other. 

Anisotropic nematic, thread-like textures have been observed for both thermotropic [429, 430, 435] and lyotropic [436] LCPs. It is interesting that rheo-optical studies [437] of a slow cooled thermotropic LCP and a high density non-LCP polyethylene both exhibit sinular textures in polarized light [437]. These are shown in a nematic LCP (Fig. 5.84) and for comparison in polyethylene (Fig. 5.3). The textures appear similar except for their size scales. 

Raudsepp A, Callaghan PT (2008) A rheo-optical study of shear rate and optical anisotropy in womUike micelles solutions. Soft Matter 4(4) 784-796... 

RHEO-OPTICAL STUDIES OF THE THERMOTROPIC AROMATIC COPOLYESTERS OF POLY(ETHYLENE TEREPHTHALATE) AND />-ACETOXYBENZOIC ACID... 

RHEO-OPTICAL STUDIES OF THE THERMOTROPIC AROMATIC COPOLYESTERS 181... 

Rheo-Optical Studies of High Polymers, Onogi Laboratory, Kyoto University, Kyoto,... 

IR rheo-optical studies of polymers advanced to a great extent in the 1980s and 1990s. In particular, Siesler carried out extensive rheo-optical IR studies of various polymer... 

Although the effectiveness of the dynamic methods using a small-amplitude oscillatory strain to the rheo-optical studies of polymeric materials was demonstrated successfully from early days for birefringence, " light scattering, " and X-ray diffraction, relatively little had been reported on the use of IR probe, " " " until the introduction of DIRLD spectroscopy. " Because of the specificity of IR to certain submolecular constituents of the system, such a combination provides useful and direct information on the molecular origin of localized time-dependent deformation and relaxation behavior of materials. 

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