Polymer interactions with solvent

As a consequence of their size, polymers interact with solvents in a more complex fashion... 

Developments in polymer science paralleled developments in describing concepts of compatibility and descriptions of polymer interaction with solvents or plasticizers, which are components of systems having a complex phase state (fiom the theory of polymer solutions). It was the development of the theory of polymer solirtions that actually promoted the development of compatibihty theories. 

It is apparent from an examination of Table 9.2 that the Mark-Houwink a coefficients fall roughly in the range 0.5-1.0. We conclude this section with some qualitative ideas about the origin of these two limiting values for a. We consider a polymer molecule consisting of n repeat units, and two different representations of its interaction with solvent. 

Crystalline polar polymers and solvents It has already been pointed out that at temperatures well below their melting point crystalline non-polar polymers will not interact with solvents, and similar considerations can apply to a large number of polar crystalline polymers. It has, however, been possible to find solvents for some polar, crystalline polymers such as the nylons, polyvinyl chloride and the polycarbonates. This is because of specific interactions between polymer and solvent that may often occur, e.g. by hydrogen bonding. 

A special case of polymorphic forms can be considered the clathrates, that is forms in which polymer molecules interact with solvents in the crystalline state and form inclusion compounds. 

The pore structure of most cross-linked polystyrene resins are the so called macro-reticular type which can be produced with almost any desired pore size, ranging from 20A to 5,000A. They exhibit strong dispersive type interaction with solvents and solutes with some polarizability arising from the aromatic nuclei in the polymer. Consequently the untreated resin is finding use as an alternative to the C8 and Cl8 reverse phase columns based on silica. Their use for the separation of peptide and proteins at both high and low pH is well established. 

Apart from paints, electrokinetic separations find limited application for synthetic polymers [905], mainly because of solvent compatibility (CE is mostly an aqueous technique) and competition of SEC (reproducibility). Reasons in favour of the use of CE-like methods for polymer analysis are speed, sample throughput and low solvent consumption. Nevertheless, CE provides some interesting possibilities for polymer separation. Electrokinetic methods have been developed based on differences in ionisation, degree of interaction with solvent constituents, and molecular size and conformation. 

Interestingly, similar non-Arrhenius kinetics is found in computer simulations of simple models that do not consider interactions with solvent. At high temperature, the model polymer is highly random and has a high configurational entropy... 

The effect of the quality of the solvent on the dimensions of dendrimers has been considered [54]. The size of the dendrimers increases with an increased interaction with solvent. However, in contrast to linear polymers or regular star polymers, the exponent v in Eq. (4) was found to be independent of the quality of the solvent for high MW dendrimers [54]. 

Figure 7.53. Differential scanning calorimetry (DSC). Shown are (a) schematic of the heat-flux sample chamber (b) an example of a DSC thermogram, showing endothermic eventsbDf (c) DSC thermogram of a poly(vinyUdene fluoride)-ethyl acetoacetate polymer-solvent system, showing two melting events for the polymer due to its intermolecular interactions with solvent molecules. The inset shows a comparison between the pure polymer (b) and the polymer-solvent (a). Reproduced with permission from Dasgupta, D. Mahk, S. Thierry, A. Guenet, J. M. Nandi, A. K. Macromolecules 2006, 39,6110.

Polymers Interact with surfactants and mlcroemulslons In diverse. Interesting and technologically Important wavs(1.21. The mechanisms that are responsible for the Interactions Include the usual panoply of forces Involved In the interaction of any two different molecules lon-lon, lon-dlpole, dlpole-dlpole, and van der Waals forces all modulated by the presence of solvent and/ or other species such as dissolved salts. All may play a role. The special factors Involved in surfactant/polymer and polymer-/mlcroemulslon Interactions that form the basis for their particular interest lies in their tendencies to form a variety of supermolecular clusters and conformations, which In tuim may lead to the existence of separate phases of coexisting species. Micelles may form In association with the polymer, polymer may precipitate or be solubilized, mlcroemulslon phase boundaries may change, and so on. 

The dry state morphology obtained from gas sorption experiments does not reveal how the material interacts with solvents. In addition to the measurement of swelling and solvent uptake, fluorescent probes can be incorporated in the polymer network and used to measure the extent of solvation of the polymer in a given solvent [51,54]. For this purpose Shea and co-workers incorporated dansyl... 

If the data presented by Rider (12, 13) is considered then one would expect a solvent/polymer interaction with all of the previously mentioned solvents with the exception of the alcohols and possibly dioxane. However, if one considers the generalized rule of Seymour (, 20) and the hydrogen bonding potential... 

The hydrogenation reaction is also sensitive to the structure of the alcohol comonomer, with the primary alcohols of the hydroxyethyl methacrylate polymer interacting with the catalyst to give results more closely resembling those found when ethanol is used as the solvent. Similar results were found with DIOP-type ligands (Figure 4). 

When a polymer molecule moves in a dilute solution it undergoes frictional interactions with solvent molecules. The nature and effect of these frictional interactions depend upon the size and shape of the polymer molecule. Thus, the chain dimensions of polymer molecules can be evaluated from measurements of their frictional properties [25]. 

The chemical properties of the CEP structure determine the ability to recognize particular stimuli and respond to them appropriately. In addition, these properties determine how the conducting polymer interacts with other materials in the construction of composite intelligent material structures. Most polymers are capable of, and indeed do, interact with other molecules. Such molecules may be part of larger molecular structures (important in the area of compatible materials), or they may be solvent molecules (such interaction can influence many processes including dissolution) or specific molecules in a solvent or gaseous medium. 

Conformations of polymer chains in dilute solutions under theta conditions are essentially identical to the random coil conformations of chains in amorphous polymers [26], where the interactions of polymer chains with solvent molecules are replaced by interactions between polymer chains. The density and the refractive index in the amorphous limit of a polymer are therefore the appropriate values of pP and nP to use in calculating the specific refractive index increment via Equation 8.16. The correlation developed for V(298K) in Section 3.C was hence used to calculate pP, and the correlation developed in Section 8.C was used to calculate nP. 

For bulk polymerization [M]e can have only one unique value at a given temperature. When solvent is added and the corresponding parameters include the interaction with solvent, [M]e depends on the nature and volume fraction of solvent, thus on [M]o as discussed on p. 6. This effect has been neglected in earlier work which led to serious mistakes in the kinetic treatment of THF polymerization (cf. Part I, and Ref.80)). Leonard has attempted to account for the interactions between monomer, polymer and solvent (Eq. 2-21) in evaluating AHlc and ASlc. These values (No. 14) have already been discussed in Sect. 2.4. 

The theory of IR (or FTIR) and Raman spectroscopy has been reviewed in several monographs (i-3) and various general references on Raman spectroscopy (3-6). The objective of this review is to survey the spectroscopic results obtained for various water-soluble polymers and to evaluate recent experimental techniques. In particular, this chapter will focus on the studies of selected water-soluble polymers and copolymers and their interactions with solvents and surfactants. 

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