Aqueous solutions chain polymers

So, the PVA/poly(sodium styrene sulphonate) [PSSNa] blend was obtained by casting aqueous solution of polymers mixture (PVA with Mw= 124,000-186,000 and HD=99% and PSSNa with Mw= 70,000). The resulted films were crosslinked with 1,2-dibromethane in gaseous phase. A semi-interpenetrating network (SIPN) in which polyelectrolyte (PSSNa) chains are trapped inside a based PVA network was obtained [44], A totally miscible blend with a very good film clarity and high mechanical resistance [44] resulted. 

Finkelmann, H., Lehmann, B. and Rehage, G. Phase behaviour of lyotropic liquid crystalline side chain polymers in aqueous solutions. Colloid Polymer Sci. 260, 56 (1982)... 

As another example, let s consider the chemical reactions that are used to prepare ion exchange resins. These resins are composed of small polymer beads that can be used to exchange one ion for another in aqueous solutions. The polymer that is used in these applications is a cross-linked polystyrene. To make this material, styrene containing a small amount of divinylbenzene is polymerized. Each vinyl group of divinylbenzene can become part of a separate polymer chain, so these groups act as cross-links between chains. The resulting polymer is used in the form of small beads that are completely insoluble in typical solvents. 

G. Berth, H. Dautzenberg, The degree of acetylation of chitosans and its effect on the chain conformation in aqueous solution, Carbohydr. Polym. 47 (2002) 39-51. 

Poly(ethylene oxide) (PEO) is a nedominantly hydrophilic polymer, and in aqueous solutions the polymer chain is highly swollen, with up to approximately... 

Typical examples are networks in aqueous solutions of polymers with short hydrophobic chains attached at both chain ends (telechelic polymers), such as hydrophobic poly(ethylene oxide), hydrophobic ethoxylated urethane (called HEUR) [1-5], hydrophobic poly(A -isopropylacrylamide) [6,7], poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) triblock copolymers [8-10], etc. These networks are analogous to the polymer networks whose elastic properties are studied in Chapter 4. They differ, however, in the important point that the network junctions can break and recombine. We extend the theoretical framework of rubber elasticity to suit for the study of polymer networks with temporal cross-link junctions. 

Optically active polymers show another properties namely thermosensitivity, e.g., main chains helical poly(iV-isopropylacrylamide) and thermosensitive part as side chain of poly(A -isopropylacrylamide) (PNlPAm). Such type of polymers synthetic method described elsewhere [137]. The polymer with optically active cores (helical polyacetylenes) and thermosensitive shells (PNlPAm) brashes self-assembled core/shell structured nanoparticles in aqueous solution. Another example of optically active polymer is poly[/V-(L)-(l-hydroxymethyl)-pro-pylmethacrylamide] (P(l-HMPMA)) of lower critical solution temperature and thermosensitivity. Circular dichroism and microcalorimetric measurements of the polymer showed the polymer chains in a state of relatively low hydration compared to that of by racemate synthesized monomers by free-radical reaction formed P(d,l-HMPMA). Thermosensitivity and structural effects were obtained by microscopic observation of aqueous solution of polymers and its hydrogels [138]. 

Ethylene oxide/styrene block copolymers have been further free-radical copolymerized with other ethylenically unsaturated compounds such as methyl methacrylate and methacrylic acid in benzene, tetrahydrofuran, and dimethylformamide (176). Correlations were made between reactivity ratio and solvent dielectric constant, as well as between solubility parameters of reaction solvent and growing polymer chains with marked effects apparent. Gel permeation chromatography of diblock and triblock copolymers based on polystyrene and poly(ethylene oxide) has revealed interesting molecular characteristics (177). Such block copolymers have an amphiphilic character. In aqueous solution, the polymers form spherical micells with a polystyrene core and a poly(ethylene oxide) outer sheath. The investigations used an aqueous-methanolic solution and were able to ascertain block copolymer structures and to estimate the impurities in the diblock copolymer. 

Glass-Transition Temperature. The T of PVP is sensitive to residual moisture (75) and unreacted monomer. It is even sensitive to how the polymer was prepared, suggesting that MWD, branching, and cross-linking may play a part (76). Polymers presumably with the same molecular weight prepared by bulk polymerization exhibit lower T s compared to samples prepared by aqueous solution polymerization, lending credence to an example, in this case, of branching caused by chain-transfer to monomer. 

The terminal R groups can be aromatic or aliphatic. Typically, they are derivatives of monohydric phenoHc compounds including phenol and alkylated phenols, eg, /-butylphenol. In iaterfacial polymerization, bisphenol A and a monofunctional terminator are dissolved in aqueous caustic. Methylene chloride containing a phase-transfer catalyst is added. The two-phase system is stirred and phosgene is added. The bisphenol A salt reacts with the phosgene at the interface of the two solutions and the polymer "grows" into the methylene chloride. The sodium chloride by-product enters the aqueous phase. Chain length is controlled by the amount of monohydric terminator. The methylene chloride—polymer solution is separated from the aqueous brine-laden by-products. The facile separation of a pure polymer solution is the key to the interfacial process. The methylene chloride solvent is removed, and the polymer is isolated in the form of pellets, powder, or slurries. 

The cyclic trimer (trioxane) and tetramer are obtained by a trace of sulphuric acid acting on hot formaldehyde vapour (i) Figure 19.1). Linear polymers with degrees of polymerisation of about 50 and a terminal hydroxyl group are obtained by evaporation of aqueous solutions of formaldehyde (ii). In the presence of strong acid the average chain length may be doubled. Evaporation of methanol solution leads to products of type (iii). 

Different samples of aqueous solution containing radionuclides of Co and Eu were prepared at different copper sulphate concentrations and constant polymer concentrations (pAM) of 15 mg/1. The addition of salt to the system was done to reduce both the repulsion forces between the radionuclides and the interaction between the polymeric chains [7]. The polymer efficiency for the prepared samples was determined, results are shown in Fig. 15. It is clear that the polymer efficiency for Eu " is higher than for Co. This can be explained by the difference in the tightly bound structured water associated with different cationic species [14,107]. On this basis, we expect that Co is more hydrated than Eu. This is due to the difference in the ionic size. The hydra-... 

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