At sufficiently elevated temperatures, polymeric materials are subject to chemical reactions that affect their structural properties. These structural changes are reflected in the viscoelastic behavior of the polymeric materials. Such viscoelastic behavior, induced by chemical reactions, may be termed chemorheology. Chemorheology is, therefore, a new field of theology that encompasses the physical and chemical aspects involved in the elucidation of the mechanism, at a molecular level of structural changes of polymers during their degradation. This paper deals with the basis and the new information of application of chemorheology.

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This paper describes the morphological and rheological behavior of block copolymer solutions. The data cited here are concerned mostly with commercial styrene (S) and butadiene (B) copolymers of SB-diblock (Solprene 1205) and SBS-triblock (Kraton 1101) type. The emphasis is placed on the following two aspects: One is to compare the behavior of SB- and SBS- block copolymers dissolved in solvents such as n-tetradecane (C14) and n-decane, which are preferentially good to B-blocks but nonsolvent to S-blocks (we call them B-selective solvents). The other aspect is to describe and examine the nature of peculiar morphological and rheological transitions exhibited by changing temperature and concentration of SB/C14 solutions.
The morphological features, the shape and size of microphase-separated domains exist in SB and SBS solutions, are essentially similar to each other, if the latter is regarded as an S-B/2 diblock copolymer. However, their rheology, especially in B-selective solvents, are entirely different, because S-cores are interconnected with B-blocks and therefore SBS-molecules form a quasinetwork structure in the SBS solutions. The quasinetwork structure imparts highly elastic and viscous properties to the SBS solutions. On the other hand, in the SB solution, SB-molecules form micelles with S-aggregates as the cores and soluble B-blocks as the cilia stabilizing the micelles. The SB/C14 micelle systems exhibit viscoelastoplastic behavior (with yield stress). Upon raising temperature or decreasing concentration, the SB/C14 solutions exhibit a transition from the viscoelastoplastic behavior to non-Newtonian (viscoelastic) and to Newtonian (viscoelastic) behavior (similar to a second-order fluid).
Small-angle-x-ray-scattering studies on the SB/C14 solutions revealed that the rheological transition corresponds to the morphological transition from a simple-cubic macrolattice structure of the micelles to disordered suspension of the micelles and to homogeneous solution (at high temperatures) or a highly dilute suspension of the micelles (in low concentrations).

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Flow properties of some typical thermotropic cholesteric liquid crystals have been studied. Measurements on cholesteryl acetate, cholesteryl myristate, cholesteryl oleyl carbonate, and some melt-mixed samples of cholesteryl chloride and cholesteryl oleyl carbonate have been carried out by means of a cone-and-plate type rheometer at their cholesteric liquid crystal temperatures. Steady flow behavior of these cholesteric liquid crystals is well described in terms of Bingham type equations, except at very high rates of shear. The deviations from the Bingham flow at high rate of shear may be attributed to the occurrence of a fracture, which was clearly seen by the use of quartz cone-plate.

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An equation for the powder discharge from a conical vessel (hopper) is derived theoretically by coupling the velocity and the stress fields for falling non-cohesive powders. The derivation is based on the analysis by Savage. In cohesive powder systems, we assume that a cylindrical block of a certain height is formed at the bottom (orifice) of the hopper and it moves out from the hopper. The block height is calculated from a dynamic force balance and a discharge equation is derived for the falling block. The equation gives a velocity profile of periodic discharge of powders. This is similar to the results by Tanaka et al., in which the motion of powder was analysed by using different values for static and dynamic Rankin's coefficients.

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We have measured the extensional complex compliance D^* at the frequency of 110 Hz with varying the temperature from 20°C to 45°C for six kinds of surgical sutures, most commonly used. Three of the samples are absorbable sutures, Plain, Chromic and Dexon, and the others are nonabsorbable ones, Silk, Nylon and Nespolen. Apparatus used was the Rheovibron DDV-II-C of Toyo Baldwin Co., which was modified to convert the direct signals of both stress and strain simultaneously to digital ones, to store them in mini floppy disks and to calculate D^* by the least square method with Signal Analyzer SM-2100 of Iwatsu Electric Co.

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