Strain Syndiotactic

In this section, various types of topochemical behaviour such as the even-numbered degree of polymerization mechanism, topochemical induction into the syndiotactic structure, stereo- and enantio-selective reactions, and the formation of highly strained cyclophanes are described. 

The theory of strain birefringence is elaborated in terms of the RIS model as applied to vinyl polymer chains. Additivity of the polarizability tensors for constituent groups is assumed. Stress-birefringence coefficients are calculated for PP and for PS. Statistical weight parameters which affect the incidences of various rotational states are varied over ranges consistent with other evidence. The effects of these variations are explored in detail for isotactic and syndiotactic chains. 

Differential IR dichroism was used to follow the dynamic strain-induced orientation of the constituent chains in PVC/PCL and NC/PCL blends. It was found for amorphous compatible blends that PCL oriented in essentially the same manner as NC and the isotactic segments of PVC. Syndiotactic PVC segments showed much higher orientation functions, which implied the existence of a microcrystalline PVC phase. 

Syndiotactic polystyrene will strain-induce crystalhze, as well as quiescently crystallize as discussed previously. Furthermore, imder certain conditions, it may also be quenched to the amorphous state. In injection molded parts, these processes may lead to skin/core differences in morphology that can be observed (111,112). With higher temperature molds (>150°C) the parts are generally fully... 

Barony et al. [69] studied the effect of ultraviolet radiation on the tensile strength of syndiotactic polypropylene. Both tensile strength and strain values changed... 

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