Polymer interactions, binary

The physical reason for the inherent lack of incentive for mixing in a polymer-polymer system is related to that already cited in explanation of the dissymmetry of the phase diagram for a polymer-solvent binary system. The entropy to be gained by intermixing of the polymer molecules is very small owing to the small numbers of molecules involved. Hence an almost trivial positive free energy of interaction suffices to counteract this small entropy of mixing. 

The majority of the scientific literature describes capsules produced through binary polymer interactions. The most typical capsule is based on alginate-polyly-... 

It should also be noted that ternary and higher order polymer-polymer interactions persist in the theta condition. In fact, the three-parameter theoretical treatment of flexible chains in the theta state shows that in real polymers with finite units, the theta point corresponds to the cancellation of effective binary interactions which include both two body and fundamentally repulsive three body terms [26]. This causes a shift of the theta point and an increase of the chain mean size, with respect to Eq. (2). However, the power-law dependence, Eq. (3), is still valid. The RG calculations in the theta (tricritical) state [26] show that size effect deviations from this law are only manifested in linear chains through logarithmic corrections, in agreement with the previous arguments sketched by de Gennes [16]. The presence of these corrections in the macroscopic properties of experimental samples of linear chains is very difficult to detect. 

For sub-micron silica particles with grafted PDMS (up to 22 K), a different result was obtained (Yates and Johnston, 1999). The particles were unstable and flocculated well above the UCSD of the PDMS-C02 binary system. These results may suggest that it is necessary to raise the density to the UCSD for PDMS at infinite molecular weight (theta density). Another possibility is that the parameters used in the theory and simulation are not applicable to PDMS, since the polymer-polymer interactions are far stronger than the polymer-C02 interaction, unlike the case for PFOA. 

The starred interaction parameters have their usual significance. It was noted that, in this instance, x 3 may represent a better picture of polymer-polymer interaction than X23 since binary mixtures of poly(e-caprolactone) and poly(vinyl chloride) are known to be stable and a small or even negative interaction parameter would be ex-... 

The usefulness of inverse gas chromatography for determining polymer-small molecule interactions is well established (1,2). This method provides a fast and convenient way of obtaining thermodynamic data for concentrated polymer systems. However, this technique can also be used to measure polymer-polymer interaction parameters via a ternary solution approach Q). Measurements of specific retention volumes of two binary (volatile probe-polymer) and one ternary (volatile probe-polymer blend) system are sufficient to calculate xp3 > the Flory-Huggins interaction parameter, which is a measure of the thermodynamic... 

Huang J, Wigent RJ, Schwartz JB (2008) Drug-polymer interaction and its significance on the physical stability of nifedipine amorphous dispersion in microparticles of an ammonio methacrylate copolymer and ethylcellulose binary blend. J Pharm Sci 97 251-262. 

This chapter summarizes the available data (x and / parameters) for polymer-polymer interactions in the melt state. The equations that are necessary to convert x parameters into binary homopolymer blend phase diagrams are also provided. We also summarize methods for predicting the properties of nanostructures with interfaces that are stabilized by the presence of block copolymers. 

The binary interactirMi generally refers to the interactions between polymer-polymer and polymer-solvent The nature of solvent-polymer interaction plays an important role in the miscibility of blends. Many thermodynamic properties of polymer solutions such as solubility, swelling behavior, etc., depend on the polymer-solvent interaction parameter (y). The quantity was introduced by Flory and Huggins. Discussions of polymer miscibility usually start with Flory-Huggins equation for free energy of mixing of a blend (refer to Chap. 2, Thermodynamics of Polymer Blends ). 

Table 6 shows that the surface of polycarbonate with adsorbed serum albumin is the most suitable one to be used in implant devices. The behavior of all lipids toward blood-polymer interaction is not similar and may change depending on the nature of lipid, net charge of the lipid-adsorbed surface and the lipid-protein/ lipid-platelet interaction at the interface. Under conditions of high cholesterol concentrations addition of vitamin C leads to suitable surface characteristics of polycarbonate. The question is how to garantee the preferential the albumin adsorption on an implant surface In works of Malmsten and Lassen [123] competitive adsorption at hydrophobic surfaces from binary protein solutions was... 

In Section 1.4.2, we derived Rp = for an excluded-volume chain using Flory s method. Here, we use a similar method to derive Rp = for theta chains. The difference in the free energy A<,h of the chain is in the second term of Eq. 1.63. For the theta chains, binary interaction is effectively absent (A2 = 0) and therefore the leading term in the polymer-polymer interaction is b R (N/R y = b N /R, which is due to the ternary interactions. Then, Ajh is given as... 

Miscibility in polymer blends is controlled by thermodynamic factors such as the polymer-polymer interaction parameter [8,9], the combinatorial entropy [10,11], polymer-solvent interactions [12,13] and the "free volume effect [14,15] in addition to kinetic factors such as the blending protocol, including the evaporation rate of the solvent and the drying conditions of the samples. If the blends appear to be miscible under the given preparation conditions, as is the ca.se for the blends dcscibcd here, it is important to investigate the reversibility of phase separation since the apparent one-phase state may be only metastable. To obtain reliable information about miscibility in these blends, the miscibility behavior was studied in the presence and absence of solvents under conditions which included a reversibility of pha.se separation. An equilibrium phase boundary was then obtained for the binary blend systems by extrapolating to zero solvent concentration. 

The miscibility limit between thermotropic liquid crystal polymers and flexible chain polymers can be predicted by calculations corresponding to the spinodal curve at constant temperature. This miscibility is increased with the increase of the degree of disorder (y/jc,) of the liquid crystal polymer and with the decrease of the degree of polymerization. Two quantitative parameters from the Hory s lattice theory can be used to estimate the phase behavior of this kind of blend at melt processing temperature the polymer-polymer interaction parameter and the degree of disorder (y/Xj). In binary polymer blends phase separation may occur for any value of degree of disorder (y/Xj)... 

Fifty-six isothermal data sets for vapor-liquid equilibria (VLB) have been used for 15 polymer-HSolvent binaries, 11 copolymer-nsolvent binaries and for 30 polymer-polymer-solvent ternaries to study compatibility of polymer blends. The equilibrium solubility of a penetrant in a polymer depends on their mutual compatibility. Equations based on theories of polymer solution tend to be more successful when there is some kind of similarity between the penetrant and the monomer repeat unit in the polymer, e.g., for nonpolar penetrants in polymers which do not contain appreciable polar groups. Expected nonideal behavior has been observed for systems containing hydrocarbons and poly(acrylonitrile-co-butadiene). The role of intramolecular interaction in vapor-liquid equilibria of copolymer-nsolvent systems is well documented for poly(aciylonitrile-co-butadiene) that have higher affinity for acetonitrile than do polyaciylonitrile or polybutadiene. 

The term miscibility is used to describe a mixture containing two or more components able to form a one-phase (solid or liquid) system that is homogeneous down to the molecular level [2]. Thermodynamics offers an unambiguous way to predict whether a binary mixture is miscible or immiscible and provides a quantitative determination of the polymer-polymer interaction energies. This is important since the interaction between polymer-polymer pairs affects the physical and mechanical properties of miscible systems and, for immiscible ones, it determines the nature and the width of the interface between the two polymers. 

In the limit that the number of effective particles along the polymer diverges but the contour length and chain dimensions are held constant, one obtains the Edwards model of a polymer solution [9, 30]. Polymers are represented by random walks that interact via zero-ranged binary interactions of strength v. The partition frmction of an isolated chain is given by... 

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