Copolymers copolymer solutions Interpolymer

Resin and Polymer Solvent. Dimethylacetamide is an exceUent solvent for synthetic and natural resins. It readily dissolves vinyl polymers, acrylates, ceUulose derivatives, styrene polymers, and linear polyesters. Because of its high polarity, DMAC has been found particularly useful as a solvent for polyacrylonitrile, its copolymers, and interpolymers. Copolymers containing at least 85% acrylonitrile dissolve ia DMAC to form solutions suitable for the production of films and yams (9). DMAC is reportedly an exceUent solvent for the copolymers of acrylonitrile and vinyl formate (10), vinylpyridine (11), or aUyl glycidyl ether (12). 

Most of the studies in aqueous solution have been devoted to interactions between homopolymers (5-10. In these systems the mean stoichiometry between interactive groups is close to 1 1. Only a few studies have been devoted to the behaviour of homopolymer/copolymer systems (11-14. Still a variation in copolymer composition leads to a modulation in the interpolymer interaction system. In a sense, inactive groups behave as structure defects. 

This type of ion-exchange membrane is prepared by solving a polymer and a polyelectrolyte in one solvent. After that a film is casted and the solvent evaporated. For example a sulphonic interpolymer membrane can be prepared from a solution of linear polystyrene sulphonic acid, Dynel (a copolymer of acrylonitrile and vinylchloride) and dimethyl formamide (43). Other examples are given in (44,45,84, 169). 

The experimental results may be represented both by the titration curves or property-composition dependences. The extremums or bends on the titration curves indicate the formation of complexes and their composition. Thus, investigating the-possi-bility of complex formation in polyelectrolyte - nonionic polymer systems, one can use the methods of conductometric and potentiometric titration. The formation of interpolymer complexes in these systems, as some authors suggest18,211, is caused by a co-operative formation of hydrogen bonds between carboxy groups of the polyacid and oxygen atoms of nonionic polyvinylpyrrolidone or poly(ethylene glycol) and is therefore accompanied by an increase of pH of the solution. The typical titration curves for the system polyvinylpyrrolidone - copolymer maleic anhydride and acrylic add are shown in Fig. 1. The inflection points of the titration curves indicate the ratio at which the macromolecular components react with each other, i.e. the composition of the formed complexes. 

The studied systems display properties typical of complex solutions. It can thus be said that the formation of the interpolymer complexes in nonionic polymer-copolymer systems occurs in solution. 

Vinyl fluoride imdergoes free-radical polymerization.The first polymerization involved heating a saturated solution of VF in toluene at 67° C under 600 MPa for 16 hr. A wide variety of initiators and polymerization conditions have been explored. Examples of bulk and solution polymerizations exist however, aqueous suspension or emulsion method is generally preferred. Copolymers of VF and a wide variety of other monomers have been prepared. More recently, interpolymers of VF have been reported with tetrafluoroethylene and other highly fluorinated monomers, such as hexafluoropropylene, perfluorobuty-lethylene, and perfluoroethylvinylether. 

Triblock and random polyampholytes based on DMAEM-MMA-MAA were examined for their phase separation behaviour [52]. Triblock polyampholytes have a much broader phase separation region than the random ones. The specific structure of PMAA-fc-PlM4VPCl with the excess of cationic or anionic blocks at the lEP is close to the structure of non-stoichiometric IPC. It is suggested that its nucleus consists of intraionic IPC surrounded by cationic blocks protecting it from precipitation [53]. ABC triblock copolymers of polystyrene-b/ock-poly(2-(or 4)vinylpyridine)-fc/ock-poly(methacrylic acid) were synthesized by living anionic polymerization [53 a]. Interpolymer complexation of the polyvinylpyri-dine and poly(methacrylic acid) blocks in the micellar solution was studied in relation to pH in solution by potentiometric, conductimetric and turbidimetric titration and in bulk by FTIR spectroscopy. 

We further characterized this copolymer mixture by using an Ubbelohde viscometer to measure the solution viscosity of a mixture of D20-PMMA and T12-PMMA in tetrahydrofuran (THF). The formation of supramolecular polymers in the D20-PMMA/T12-PMMA blends provided a higher solution viscosity relative to that of pure PMMA as shown in Figure 2.15 in addition, the viscosity increased upon increasing the concentrations of the copolymers. This supramolecular polymer also could be observed macroscopically—in the form of a gel—from a 1 1 mixture of D20-PMMA/T12-PMMA in THF at a concentration of 30 g/dL at the same concentration, a solution of PMMA, which lacked any specific interpolymer hydrogen-bonding interactions, flowed freely (see the inset to Figure 2.15). 

In aqueous solutions of hydrophobically-modified water-soluble polymers, strong interpolymer hydrophobic association often leads to gelation or precipitation. It is well-known, however, that AB- and ABA-type block copolymers, where A and B represent hydrophilic and hydrophobic blocks, respectively, form micelles with a hydrophobic core and a hydrophilic corona (25). The formation of these polymer micelles is described by a closed association process (26-28), and at a thermodynamic... 

Addition of sodium, potassium, calcium, ammonium, etc., bases to aqueous solutions of Gantrez AN resins leads to two viscosity peaks, corresponding to 1 and 2 mole equivalents of base. The interpolymers are precipitated by Ca ions and other heavy, polyvalent metal cations, beyond 0.7 mole equivalents. With ammonium hydroxide, peaks tend to be observed at about 1 and 3 mole equivalents of base. Ionic interactions in aqueous solutions of Gantrez AN polyelectrolytes and polycarboxylates, electrophoretic mobility and viscosity of copolymer salts, counterion binding properties, etc., have received substantial <659,672.700-702,1100) polyelectrolyte salt sol-... 

Since the micelle formation of polyAMPS-bound Ci2E moieties in aqueous solutions is mainly due to interpolymer association, an apparent cmc is observed. Here, the apparent cmc is defined as a polymer concentration for the onset of interpolymer association. Apparent cmc for polyAMPS-bound Ci2Em moieties was estimated using fluorescence excitation spectra of pyrene probes (35,36). This method is based on the fact that the 0-0 absorption maximum for pyrene in water at 334 nm shifts to 337 nm when pyrene is solubilized in a micellar phase (45-48). The ratio of the intensity at 337 run relative to that at 334 run (f33 //334), estimated from excitation spectra, increases with polymer concentration (Cp). As illustrated in Figure 1 for copolymers of w = 25 with varying C12E25... 

Phase transitions in polymer-polymer and gel-linear polymer systems consisting of complexes of acrylic acid/butyl vinyl ether copolymers with linear and crosslinked poly-N-vinyIpyrrolidone, 1,2,5-trimethyl-4-vinylethynylpiperidinol-4/N-vinylpyrrolidone copolymer with linear and crosslinked polyacrylic acid, polyacrylic acid with crosslinked poly-N-vinylcaprolactam taking place as a function of internal (composition of copolymers) and external (thermodynamic quality of solvents, degree of ionization, temperature) factors have been investigated. In most cases the analogy in behavior of interpolymer complexes in a solution and gel-polymer complexes is observed. 

In aqueous solutions of amphiphilic polymers, which contain both hydrophilic and hydrophobic sequences, strong interpolymer hydrophobic association often leads to bulk-phase separation or gelation. However, there are classes of amphiphilic polymers that form well-organized associated structures in aqueous solution without accompanying macroscopic phase separation. This is generally characteristic of amphiphilic AB and ABA block copolymers, where A and B represent hydrophilic and hydrophobic sequences, respectively. These types of block copolymers and low molecular weight surfactant molecules have common features in their associating behavior. 

As the number of hydrophobic sequences in an amphiphilic polymer chain increases, intrapolymer hydrophobic association, as well as interpolymer association, becomes an important process to determine overall self-organized structures. This is particularly so with amphiphilic random or alternating copolymers in which hydrophobic and hydrophilic units are randomly or alternately distributed on a polymer chain. Intrapolymerassociating structures are of critical importance to determine interpolymerassociating structures. In general, intrapolymer hydrophobic association is dominant in dilute solutions, whereas interpolymer association also occurs in a semidilute or concentrated regimen. In random copolymers with a strong tendency for intrapolymer association, unimolecular micelles (unimer micelles) may be formed as a consequence of intrapolymer closed association. 

In general, unimer micelles are preferentially formed in highly dilute aqueous solutions. As the concentration is increased, however, the hydro-phobic association may not necessarily be an intrapolymer event. If interpolymer open associations occur between the hydrophobes or between the primary micelle units, multipolymer aggregates would be formed instead of the unimer micelles. Whether the intrapolymer closed association predominates over the interpolymer open association depends on primarily the chemical structure or the first-order structure of amphiphilic random copolymers. 

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