Chain dimensions, polyimide

Comparison of Chain Dimensions. Knowledge of the intrinsic viscosities and molecular weights of a series of PMDA/DAPE polyamic acids allows estimation of the unperturbed chain dimensions. Comparison may then be made with the cured polyimide, with results obtained by other workers, and with calculated values. The expressions in the literature using values for [n] obtained in good solvents generally involve extrapolation of [t)]/M toM = 0, where excluded volume effects are presumed to be minimal (12-14). Although this method is not strictly valid, it is useful for comparison purposes when direct measurement of the dimensions is impractical. The data in Table I for the polyamic acid in distilled NMP and in the poorer mixed solvent NMP/dioxane yield (see Figure... 

Swift heavy ion beams with extremely high LETs are used to degrade strongly polymer chains within tracks over a range of a few tens of micrometers. After irradiation, the top surface of bulk thermoplastics such as polyethyleneterephtalate, polycarbonate, polyvinylidene fluoride or polyimide materials as well as thin films made of the same material are subsequently etched by a wet chemical treatment that reveals pores of which the shape, surface density and dimensions can be controlled by choosing appropriate conditions. High aspect ratio cylindrical or conical traces of diameter ranging from a few nanometers to some... 

In this context, some works investigated a series of blends obtained from hydroxy-propyl cellulose in lyotropic phase, and a new partial aHphatic polyimide (PI) or its poly(amic acid) precursor (PAA) [104]. The flow behavior of their mixed solutions in N,N-dimethylacetamide shows the effect of composition, temperature and shear rate on the orientation or mobiHty of the chain segments in the shear field. Specific interactions, such as the hydrogen bonds between PAA and the liquid crystalHne component, stabilized the resulted morphology. The band texture, typical for lyotropic HPC solutions, evidencing different intensities and dimensions is observed from atomic force microscopy images in PAA/HPC and PI/HPC blends (Figure 14.7) [104]. 

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