Mixture of poly

Mixtures of polymers at surfaces provide the interesting possibility of exploring polymer miscibility in two dimensions. Baglioni and co-workers [17] have shown that polymers having the same orientation at the interface are compatible while those having different orientations are not. Some polymers have their hydrophobic portions parallel to the surface, while others have a perpendicular disposition. The surface orientation effect is also present in mixtures of poly(methyl methacrylate), PMMA, and fatty acids. 

These association reactions can be controlled. Acetone or acetonylacetone added to the solution of the polymeric electron acceptor prevents insolubilization, which takes place immediately upon the removal of the ketone. A second method of insolubiUzation control consists of blocking the carboxyl groups with inorganic cations, ie, the formation of the sodium or ammonium salt of poly(acryhc acid). Mixtures of poly(ethylene oxide) solutions with solutions of such salts can be precipitated by acidification. 

Emulsions of fatty- and petroleum-based substances, both oils and waxes, of the o/w type are made by using blends of sorbitan fatty esters and their poly(oxyethylene) derivatives. Mixtures of poly(oxyethylene(20)) sorbitan monostearate (Polysorbate 60) and sorbitan monostearate are typical examples of blends used for lotions and creams. Both sorbitan fatty acid esters and their poly(oxyethylene) derivatives are particularly advantageous in cosmetic uses because of their very low skin irritant properties. Sorbitan fatty ester emulsifiers for w/o emulsions of mineral oil are used in hair preparations of both the lotion and cream type. Poly(oxyethylene(20)) sorbitan monolaurate is useflil in shampoo formulations (see Hairpreparations). Poly(oxyethylene) sorbitan surfactants are also used for solubilization of essential oils in the preparation of colognes and after-shave lotions. 

Allylchlorosilanes reacted with naphthalene to give isomeric mixtures of poly-alkylated products. However, it was difficult to distill and purify the products for characterization from the reaction mixture due to the high boiling points of the products and the presence of many isomeric compounds. The alkylation of anthracene with allylchlorosilanes failed due to deactivation by complex formation w ith anthracene and the self-polymerization of anthracene to solid char. 

Chang, R. K., Price, J. C., and Whitworth, C. W., Control of drug release rates through the use of mixtures of poly-caprolactone and cellulose propionate polymers, Pharm. Technol. 10, 24, 26, 29, 32-33, 1986. 

Other hand, when an equimolar mixture of 2,5-DSP and l OEt is recrystallized from benzene, yellow crystals, comprising 2,5-DSP and l OEt in a molar ratio of 1 2, deposit. In the DSC curve of this crystal, a single endothermic peak is observed at 166°C, which is different from the melting point of either 2,5-DSP (223°C) or l OEt (156°C). Furthermore, the X-ray powder diffraction pattern of the crystal is quite different from those of the homocrystals 2,5-DSP and l OEt. Upon irradiation the cocrystal 2,5-DSP-l OEt affords a crystalline polymer (77i h = 1.0 dl g in trifluoroacetic acid). The nmr spectrum of the polymer coincides perfectly with that of a 1 2 mixture of poly-2,5-DSP and poly-1 OEt. In the dimer, only 2,5-DSP-dimer and l OEt-dimer are detected by hplc analysis, but the corresponding cross-dimer consisting of 2,5-DSP and l OEt is not detected at all (Hasegawa et al., 1993). These observations by nmr and hplc indicate that the photoproduct obtained from the cocrystal 2,5-DSP-l OEt is not a copolymer but a mixture of poly-2,5-DSP and poly-l OEt in the ratio 1 2. 

Quite often in the ring-opening polymerization, the polymer is only the kinetic product and later is transformed to thermodynamically stable cycles. The cationic polymerization of ethylene oxide leads to a mixture of poly(ethylene oxide) and 1,4-dioxane. In the presence of a cationic initiator poly(ethylene oxide) can be almost quantitatively transformed to this cyclic dimer. On the other hand, anionic polymerization is not accompanied by cyclization due to the lower affinity of the alkoxide anion towards linear ethers only strained (and more electrophilic) monomers can react with the anion. 

A second method for preparing block copolymers is a crosscoupling process. A low molecular weight coupling reagent is added to a mixture of poly(phenylene oxide) and a second homopolymer with phenolic hydroxyl endgroups such as 7 (9) or 8 (10) in the presence of sodium hydroxide and catalyst. 

Figure 10 Separation of a homopolymer mixture of poly (ethyl methacrylate) (PEMA), polystyrene (PSTY) and poly (lauryl methacrylate) (PLMA) by Orthogonal Chromatography at different % n-heptane concentrations in SBC 2.

Poly(4-vinylpyridine) was used also as a template for polymerization of maleic anhydride. Maleic anhydride is very difficult to polymerize by conventional radical polymerization, but in the presence of poly(4-vinylpyridine) in chloroform or in nitromethane, polymerization proceeds at room temperature just after mixing 0.5% solution of poly(4-vinylpyridine) with 1% solution of maleic anhydride. A yellow precipitate is obtained. The precipitate is a mixture of poly(maleic anhydride), poly(4-vinylpyridine), and unreacted maleic anhydride. In the absence of oxygen, polymerization is much slower. The reaction stops on the stage of donor-acceptor complex formation. 

The authors found that 4- and 2-vinylpyridines and N,N-dimethylaminostyrene polymerize spontaneously at 50°C in DMF or acetone in the presence of poly(maleic anhydride). Product obtained consist of 1 1 mixture of poly(vinylpyridine) and the template. Moreover, degree of polymerization of daughter polymer was almost the same as degree of polymerization of the template used. After separation of the polymerization product, it was found that for PVP, P = 14, whereas for poly(maleic anhydride) used as a template, Pn = 12. 

Fig. 27. Plastogram of a mixture of poly(vinyl chloride) (21 g) and methyl methacrylate (intermolecular monomer) (8 ml) (86)...

When the formaldehyde concentration at the start is high (36 weight %), the product is a mixture of poly(formaldehyde) and a formaldehyde/thioformaldehyde copolymer. 

Non-microencapsulated mixtures of poly (DL-lactic acid) and phenobarbitone (ratios 1 1 and 1 2) were prepared by mixing the powders for 10 min. 

A different approach has been used by Tsuda, Nakane and their collaborators (138,139) who showed that mixtures of poly(methylisopropenyl ketone) (PMIPK) containing a bisazide sensitizer such as 4,4 -diazodiphenyl sulfide or 4-methyl-2,6-di(4-azidobenzylidene) cyclohexanone function as negative dry-developable resists. It is claimed that the bisazide... 

Suzuki et al. reported cloud-point temperatures as a function of pressure and composition in mixtures of poly(ethyl acrylate) and poly(vinylidene fluoride) [9], Their data in terms of p(T) curves at constant composition show that miscibility in the same system may either improve or decline with rising pressure, depending on the blend s composition. Important consequences for blend-processing ensue. A planned two-phase extrusion may easily be jeopardized by the pressure building up in the extruder. Conversely, a homogeneous melt may be turned into a two-phase system when the pressure on the blend increases. 

EOS models were derived for polymer blends that gave the first evidence of the severe pressure - dependence of the phase behaviour of such blends [41,42], First, experimental data under pressure were presented for the mixture of poly(ethyl acetate) and polyfvinylidene fluoride) [9], and later for in several other systems [27,43,44,45], However, the direction of the shift in cloud-point temperature with pressure proved to be system-dependent. In addition, the phase behaviour of mixtures containing random copolymers strongly depends on the exact chemical composition of both copolymers. In the production of reactor blends or copolymers a small variation of the reactor feed or process variables, such as temperature and pressure, may lead to demixing of the copolymer solution (or the blend) in the reactor. Fig. 9.7-1 shows some data collected in a laser-light-scattering autoclave on the blend PMMA/SAN [46],... 

Mixtures of poly(vinylidene fluoride) with poly (methyl methacrylate) and with poly (ethyl methacrylate) form compatible blends. As evidence of compatibility, single glass transition temperatures are observed for the mixtures, and transparency is observed over a broad range of composition. These criteria, in combination, are acceptable evidence for true molecular intermixing (1, 19). These systems are particularly interesting in view of Bohns (1) review, in which he concludes that a compatible mixture of one crystalline polymer with any other polymer is unlikely except in the remotely possible case of mixed crystal formation. In the present case, the crystalline PVdF is effectively dissolved into the amorphous methacrylate polymer melt, and the dissolved, now amorphous, PVdF behaves as a plasticizer for the glassy methacrylate polymers. 

The dielectric relaxation of bulk mixtures of poly(2jS-di-methylphenylene oxide) and atactic polystyrene has been measured as a function of sample composition, frequency, and temperature. The results are compared with earlier dynamic mechanical and (differential scanning) calorimetric studies of the same samples. It is concluded that the polymers are miscible but probably not at a segmental level. A detailed analysis suggests that the particular samples investigated may be considered in terms of a continuous phase-dispersed phase concept, in which the former is a PS-rich and the latter a PPO-rich material, except for the sample containing 75% PPO-25% PS in which the converse is postulated. 

Figure 13.6 Film cast from a 1 2 mixture of poly(styrene-co-butadiene) and poly(2-vinyl pyridine-co-butadiene) with about 15 mol% butadiene content (10 wt% solution of the copolymers in tetrahydrofuran). Dark areas, poly(styrene-co-butadiene) light areas, poly (2-vinyl pyridine-co-butadiene) [15]. Courtesy of Dr A. Schindler...

The upper part of Figure 4 shows the results of the rapid density gradient centrifugation of a latex mixture of poly(styrene) and two chemically uniform co-... 

Mixtures of poly (ethylene oxide) (PEO) of various molecular weights with a -CD have given stoichiometric complexes in high yields [17]. It is important to consider that the formation of the complexes involved the threading of the a-CD along the polymer chain into a necklace-like structure [26], This process is driven... 

Gel permeation chromatography (GPC) of poly(methyl methacrylate) and cellulose nitrate showed elution volume peaks at 62.5 ml for PMMA and at 87.5 for cellulose nitrate (Figure 5), due to their difference in molecular weight. A mixture of poly(methyl methacrylate) and cellulose nitrate of the same ratio as that of the graft copolymer was recorded and two peaks in elution volume at almost identical positions were observed. This shows that the constituent homopolymers retain their identity in a physical mixture. The isolated graft copolymer showed a single peak in elution volume at 80.0 ml. The second peak in elution volume is absent in spite of poly(methyl methacrylate) attached to cellulose nitrate as revealed by infrared spectrum. Hence, these results indicate that GPC can be used as a technique to differentiate between homopolymer, physical mixture, and graft copolymer. 

Keiderling reported the VCD spectra of triple helices in ribonucleic acids by investigating the temperature dependent VCD features of a mixture of poly(rA) and poly(rU) [54]. The spectra of the triple helix are more complicated than those of a double strand, as expected. We have reported the VCD of a number of oligo deoxynu-cleotides with between four and twelve base pairs. These studies will be elaborated upon after a detailed discussion of the VCD features of polymeric DNA and RNA samples, for which the solution structures are well established. 

The drag is distributed throughout a polymer matrix. Such a system can be relatively easy to manufacture, the simplest case being when the drag is dispersed directly in a blend composed of, for example, a mixture of poly(acrylic acid) and elastomeric compounds such as poly(isobutylene) and poly(isoprene). 

And similarly (176) 2-phenyl-imino-oxazolidine and its tautomer, 2-amino-2-oxazolidine, with cationic catalyst yielded a mixture of poly(ethylene-N-phenyl urea) and a polyethylene imine type polymer ... 

The styrene monomer first may be polymerized to about 65% conversion in the absence of water, and then the blowing agent (cyclopentane) may be added with additional peroxide. This solution is suspended in water in the presence of potato starch, and the polymerization is finished (74). By another modification a styrene solution of waste polystyrene and peroxide is suspended by poly (vinyl alcohol) in water, and pentane is added to the suspension after the solids content of the oil phase is greater than 70% (133). Polystyrene particles may also be suspended in water by a mixture of poly (vinyl alcohol) and a phenyl sulfonate and then a mixture of equal parts of pentane and catalyzed styrene (8% each on polymer) is diffused into the polymer. The temperature is elevated, and the polymerization is completed (23). 

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