Kink defects

The time-resolved spectra from the run of C16 exposed to C12E04 (Figure 3) are quite different from those of the surfactant - free water run. The relative intensity of the end gauche and double gauche defect bands is increased, and the kink defect band bear 1300 cm 1 may be split into a multiplet. In addition, several bands between 1260 and 1200 cm 1 are enhanced, relative to the spectrum of the... 

Figure 3.64 Scheme showing a kink defect. The reactivity of carbon atoms is increased especially on the convex side. 

In PVF2 the major condis polymorph is orthorhombic (Cm2m) and metastable at atmospheric pressure (polymorph I, also called P). The polymorph results on drawing of melt-crystallized PVF2 or on crystallization at elevated pressure. Its chain-conformation is close to planar zig-zag with randomly disordered rotation-angles of about 7° and occasional kink-defects There is no direct transition... 

Indirect observations concerning the presence of kink defects within the hexagonal form of PE came from independent IR experiments performed at atmospheric pressure on y irradiated PE samples [228] and on ultra drawn PE yarns kept under tension at temperatures higher than the normal melting temperature of PE at atmospheric pressure [229]. 

In fact, the hexagonal form of PE may be also obtained above a critical pressure, by heating y irradiated PE samples above a certain temperature [230]. The orthorhombic to hexagonal transition temperature is a function of y ray dose, and a sufficiently high irradiation dose makes the radiation induced hexagonal phase of PE stable even at atmospheric pressure [228,230]. The radiation-induced hexagonal phase shows IR spectra with the characteristic bands of kink defects [228]. 

Fig. 25 Schematic drawing of a PE chain with a kink defect shortening the average chain periodicity from 2.55 A (corresponding to the all-fransconformation) to values close to 2.4 A. The defective region of the chain is encircled. The t parameter expresses the lateral encumbrance of kink defect along an axis perpendicular to z (chain axis). The chain portions of PE aside the defect are co-axial. (Adapted from [221])...

Standard deviation of the lateral positions of defective units, the lateral encumbrance, t, of kink defects (defined in Fig. 25) was esteemed to be about 1.6 A, in a good agreement with the lateral encumbrance of the kink model proposed in [105] by Petraccone, Allegra and Corradini. 

Side and Top View of a Kink Defect in a Paraffin Crystal... 

By inspection, one can see that the kink is the result of the collision of a transverse (A), torsional (B), and longitudinal vibration (C) between 0.5 and 1.1 ps (see also Fig. 1.47). After formation, this particular kink defect had a life time of about 2 ps. 

As shown in Sect. 3, kinks exist in the predicted concentrations (Figs. 12 and 13), but are relatively immobile in the simulations, and thus relaxation and annealing are more heavily linked to the skeletal vibrations of the molecular chains than the motion of conformational defects, although the presence of the kink defects seems to play an important role in the activation of chain diffusion (see Figs. 16-18). 

Similarly, a study of ethyl-branched ADMET PE has also been reported [139]. This work showed that these polymers favored branch inclusion, resulting in a crystal structure similar to that obtained for the precisely methyl-branched ADMET polymers. This crystallization behavior, however, was dependent on branch concentration. When the branch content was 111 ethyl branches per 1000 carbons, the resulting polymer was amorphous, indicating that the steric demands of the ethyl branches precluded their participation in crystallization. Conversely, ethyl branch contents of 50-60 branches per 1000 carbons resulted in polymers able to include the ethyl branch defects in the crystal lattice, presumably due to the presence of kink defects able to accommodate the ethyl branches. 

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