Polymer groups neutral

Introduction of small amounts of ionic groups in hydrocarbon polymers exerts a profound effect on their mechanical properties. These ionic groups neutralized with suitable metal ions act as physical cross-hnks within the polymer matrix. The ionic associations can be thermally relaxed to permit sufficient melt flow at the processing temperature. The ion containing polymer thus behaves as a thermoplastic elastomer having the unique ability to act as cross-linked elastomer at ambient temperature, and to melt and flow at elevated temperatures like thermoplastics [50-53]. 

The polymer may be modified with functional or reactive groups in a reactor or an extruder, via reactive extrusion. Polyolefin modified with maleic anhydride, acrylic acid, glycidyl methacrylate, acid groups neutralized with a metal cation (ionomer), itaconic acid, or anhydride or similar compounds have been widely reported as compatibilizers because these groups have the ability to form a chemical linkage or a polar or ionic interaction with polar polymers such as polyamides (PAs), polyesters, and others. 

Aqueous Systems. Type 6 in Table 2.5. Aqueous dispersions of polyurethanes that are slightly supported by ionic groups also undergo physical film formation. The binder consists of polymer chains that are coupled via urethane and urea groups, and contain basic or acid groups. Neutralization by salt formation provides the necessary hydrophilicity if the self-emulsifying properties resulting from incorporation of hydrophilic polyether radicals are insufficient. 

Fig. 5.2 Schematic representation of functional polymer chains configured on a cubic lattice. The darker cubes indicate a lattice site occupied by a functional end group, and the lighter cubes are occupied by polymer chain segments (a) illustrates a chain with a low-energy attractive end group, (b) depicts a nonfunctional polymer with neutral end groups. Reproduced with permission from [54]...

Related work has been done by Rubner s group for materials potentially useful to thin-film electronic and optical devices. Conjugated polymers in neutral and conducting chemistries [57-60], molecular dyes [61] and fullerenes [62] have all been stacked in multilayer arrays. Functional light-emitting diodes have been fabricated from multilayers of poly(p-phenylenevinylene) (PPV) and two different polyanions on active electrodes [63]. These devices have absorption and emission bands and photo-... 

Solubility Characteristics Hydrophilic, soluble in water, alcohol, and polar solvents Formulating Considerations Any ingredients with reactive groups (e.g., polquatemiums) should be added after polymer is neutralized Form Supplied Fine white powder Regulatory Status Benzene-free... 

The target polymer was prepared by bromotrimethylsilane-induced cleavage of the -butyl phosphonate ester group in neutral precursor polymer. After neutralization of the reaction mixture with aqueous sodium hydroxide, target polymer exhibited good solubihty in water. 

In a separate patent, Ganslaw and Katz [43] described absorbent polymers prepared from water soluble polyacrylate polymers having 40-85% of the carboxylate groups neutralized, and A13+ ion. The appropriate complex-forming ion was post-added to the anionic polyelectrolyte formed in a separate step. The resulting product was dried, and exhibited at least a 15 g/g absorbency in synthetic urine. At elevated pH the complex broke down, yet reformed at lower pH, allowing the composition to be applied to a substrate while fluid (high pH) and then crosslinked in place (lower pH). 

To illustrate the specific operations involved, the scheme below shows the first steps and the final detachment reaction of a peptide synthesis starting from the carboxyl terminal. N-Boc-glycine is attached to chloromethylated styrene-divinylbenzene copolymer resin. This polymer swells in organic solvents but is completely insoluble. ) Treatment with HCl in acetic acid removes the fert-butoxycarbonyl (Boc) group as isobutene and carbon dioxide. The resulting amine hydrochloride is neutralized with triethylamine in DMF. 

Then N-Boc-O-benzylserine is coupled to the free amino group with DCC. This concludes one cycle (N° -deprotection, neutralization, coupling) in solid-phase synthesis. All three steps can be driven to very high total yields (< 99.5%) since excesses of Boc-amino acids and DCC (about fourfold) in CHjClj can be used and since side-reactions which lead to soluble products do not lower the yield of condensation product. One side-reaction in DCC-promoted condensations leads to N-acylated ureas. These products will remain in solution and not reaa with the polymer-bound amine. At the end of the reaction time, the polymer is filtered off and washed. The times consumed for 99% completion of condensation vary from 5 min for small amino acids to several hours for a bulky amino acid, e.g. Boc-Ile, with other bulky amino acids on a resin. A new cycle can begin without any workup problems (R.B. Merrifield, 1969 B.W. Erickson, 1976 M. Bodanszky, 1976). 

In some systems, such as lake and river waters, the suspended inorganic particles may be coated by biological polymers, termed humic substances, which prevent flocculation by either steric or electrostatic mechanisms. These can also interact with added inorganic salts (31) that can neutralize charged functional groups on these polymers. 

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