Repeat units lengths

Figure 1.8 Branch cell structural parameters (a) branching angles, (b) rotation angles, (/) repeat units lengths, (Z) terminal groups and dendritic subclasses derived from branches (IVa) random hyperbranched, (IVb) dendrigrafts and (IVc) dendrons/dendrimers...

There is also an alternative numbering system for synthetic polyamides. Polymers that could be made from amino acids are called nylon-.r, where x is the number of carbon atoms in the repeating unit. Thus, polycaprolactam (1-13) is nylon-6, while the polymer from m-aminoundecanoic acid is nylon-11. Nylons from diamines and dibasic acids are designated by two numbers, in which the first represents the number of carbons in the diamine chain and the second the number of carbons in the dibasic acid. Structure 1-6 is thus nylon-6,6. Nylon-6,6 and nylon-6 differ in repeating unit length and symmetry and their physical properties are not identical. 

M is determined exactly from the repeat unit composition. The repeat unit length can be measured by using an interactive molecular modeling program. The rotational degrees of freedom of the backbone can be counted by using the rules provided in Section 4.C. The new quantitative structure-property relationships developed in this book for V and p (Chapter 3), Ecoh (Chapter 5), Tg (Chapter 6), critical molecular weight (Equation 11.25 combined with Equation 11.24), molar Rao function (Section ll.B), molar Hartmann function (Section ll.B), characteristic ratio (Chapter 12), and surface tension (Chapter 7), allow the application of various derived correlations for mechanical properties to all polymers built from the nine elements (C, N, O, H, F, Si, S, Cl and Br) included in the scope of our work. 

Figure 5 shows front view of the molecular packing of C -PAMs in the crystalline state. As to see in Figure 5, the side chains emanate laterally and tilted from the main chain backbone and the tilt angle is 15°. The repeat unit length is 13A and the distance between two neighboring side branches emanating from different main chains is determined to be 4.4A from the peak s... 

Number of equivalent bonds per repeat unit Length of an equivalent bond Molar mass of an equivalent repeat unit Number of bonds of an equivalent chain Number of bonds per polymer repeat unit Polar coordinate distance... 

Fig. 9 Branch cell structural parameters a branching angle, b rotation angle, I repeat unit length, Z terminal group, I molecular reference marker or core. Dendritic subclasses derived from branches IVa random hyperbranched, IVb dendrigrafts, and IVc dendrons/dendrimers [93]. Copyright Wiley-VCH Verlag GmbH Co. KGaA. Reproduced with permission...

The poly(ethylene terephthakte) analyzed was about 75% cr5retalline. The cr tal structure is triclinic with the moleculEu chains in an almost planar conformation. The poly(ethylene sebacate) was about 57% crystalline with a nomoclinic crystal structure with the molecular chains also in a planar conformation, in fact quite similar to the polyethylene crystal structure. The two repeating units, however, do not cocrystallize since the repeating unit lengths in the chain direction do not match. The copolymers thus show only poly(ethylene terephthalate) crystallinity. The 80/20 copolymer was about 22% crystalline, while the 60/40 copolymer was about 15% cr5retalline. 

In a copolymer system where both comonomer units are crystaUizable, co-crystallization may be observed if the comonomer units are similar in chemical structure, repeat-unit length, and/or crystal chain conformation [80]. Furthermore, a copolymer is said to be isodimor-phic if co-crystallization of the different comonomer sequences leads to the observation of two distinct crystalline phases depending on copolymer composition [80]. 

Other x-ray patterns obtained from main-chain polymers in the smectic state are characteristic of a disordered lamellar structure. " They present a sharp inner ring corresponding to the lamellar thickness and a diffuse outer ring reflecting the absence of ordering within the layer planes. For Sq phases, diffraction patterns of powder samples are essentially the same as those for except that the layer spacings are usually relatively smaller. In an phase, the director is normal to the layers which are about one repeat unit thick. The accepted structure for the Sc is that the director is tilted with respect to the layers the lamellar thickness is less than the repeat unit length. 

The integration constant C is tan Ku(0)/4 and K is 27t divided by the intrachain repeat unit length d. For a polyethylene chain with a spring constant k of 34 nN Eqs. (5.28) and (5.24) have been evaluated [22]. The crystal potential depth V has been derived as 0.0138 nN from the cohesive energy density 5 through... 

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