Homopolymer interaction potentials

Consider a number n of stiff polymer components (here stiff is used to mean semiflexible ) and define orientation-dependent ideal and interacting response (n x n) matrices X0(Q, u, u ) and X(Q, u, u ) respectively. In this case, orientational correlations have to be included in addition to the usual isotropic ones. Doi et al. [36-38] have developed the theory for solutions of stiff homopolymers. Their formalism is applied in Appendices C and D to multicomponent blend mixtures of stiff polymers without and with the incompressibility condition respectively. The interaction potentials comprise anisotropic (also called nematic) contributions as well as the usual isotropic ones ... 

The interaction potentials described in previous sections for adsorbing homopolymer and terminally anchored layers in good solvents clearly indicate the ability of polymers to stabilize colloidal dispersions against flocculation due to van der Waals dispersion forces. Indeed, the practice preceeded the analyses by centuries in some cases and decades in others, since the use of adsorbing polymers dates to ancient times, and block copolymer stabilizers emerged from industrial laboratories in the 1960s (Napper, 1983). 

These are chemically homogeneous multiarm star polymers (usually homopolymers) with only excluded volume interactions [21,22], Due to their synthesis procedure (high vacuum anionic polymerization), they are stable and nearly monodisperse [23]. Their softness can be tuned at the synthesis level (number and size of arms) [23,24] and/or by varying the temperature in different solvents [25,26], Moreover, these systems can be functionalized in various ways [27]. What made these systems truly ideal soft colloids were the breakthroughs in both theoretical description and synthesis. The former refers to the ability to describe analytically their internal structure [28] and their softness in terms of an effective interaction potential [24,29]. 

Equations (20) to (31) give the density distributions and free energies for systems with solvent, homopolymer, and diblock copolymer, as long as all the interaction potentials and the potential fields other copolymer architectures are similar, and in the literature. 

In the case of HI variants, linker histones selectively bind ADPr homopolymers over competitor DNA [223]. Furthermore, Hit displays a high degree of affinity for the ADPr subunits even in the presence of salt [223]. Interestingly, this testis specific variant interacts with DNA the least tightly, and has been implicated in fiber decondensation [25,226,227]. This result suggests that potential interactions between HI molecules and ADPr are specific and not just the bi-product of electrostatic attractions. In this regard, specificity for the ADPr subunits may facilitate removal of HI from chromatosomal DNA, and initiate an unraveling of the 30 nm fiber required for DNA activation or repair. Unfortunately, the... 

Conformational energies are calculated for chain segments in poly(vlnyl bromide) (PVB) homopolymer and the copolymers of vinyl bromide (VBS and ethylene (E), PEVB. Semlempirical potential functions are used to account for the nonbonded van der Waals and electrostatic Interactions. RIS models are developed for PVB and PEVB from the calculated conformational energies. Dimensions and dipole moments are calculated for PVB and PEVB using their RIS models, where the effects of stereosequence and comonomer sequence are explicitly considered. It is concluded from the calculated dimensions and dipole moments that the dipole moments are most sensitive to the microstructure of PVB homopolymers and PEVB copolymers and may provide an experimental means for their structural characterization. 

The scale factors e and r represent the coordinates of the minimum of the potential function E(r ). - In generalization of Eq. (7) for a mixture of two homopolymers A and B consisting of segments of types A and B one may introduce the average interaction of a segment (say A) with the neighbor segments at a distance r in terms of the volume fraction ... 

Fig. 23. Ternary blend containing two homopolymers A and B and a symmetric AB diblock copolymer within the bond fluctuation model. All chains have identical length, N = 32. (a) Probability distribution at e = 0.054 and system size 48 x 48 x 96 in units of the lattice spacing (i e = 17). Upon increasing the chemical potential S/j of the copolymers the valley becomes shallower, indicating that the copolymers decrease the interfacial tension. One clearly observes a plateau around (f> = 1/2. This assures, that our system size is large enough to neglect interfacial interactions in the measurement of the interfacial tension, (b) Average number of copolymers as a function of the composition. The copolymer number is enhanced in the configuration containing two interfaces. From Muller and Schick [105]...

The full relation for the chemical potential of the copolymers in the bulk Pbmsh can be obtained from the Flory-Huggins energy of mixing between diblock copolymers A-N and homopolymers P [259, 260], when interaction parameters %AP> %AN, and % (% =%np) are specified. In most experiments brush N-mers and homopolymer P-mers are microstructurally identical and differ only in the isotopic status. Related isotopic interaction parameter % is usually much smaller than parameters yAP and %AN. Assuming [254] Xan=X,m<+X, and neglecting volume fraction of the anchor moieties in the bulk, the expression for pbulk is obtained in the form... 

The cost and usefulness of co-additives might be considered as coimter-remedies for restoring properties. For example 5% silicone modifier additions have been shown to nearly double notched Izod impact strength in PP compounds, potentially raising the impact of an FR-PP to near the level of neat PP. Or, given that PP copolymers require more phosphorous FR than homopolymers, a materials selector might choose a less-expensive, impact-modified homopolymer FR-PP instead. This attention to property interactions can save costs, as long as the FR is not interfered with by the chosen modifier [5-13, 5-19). 

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