Strong polybase

The strong polybase behavior of PMVE is well documented, and interest in this polymer, especially from academic workers, suggests eventual interest industrially. This feature of PMVE cannot be found in acrylates or other inexpensive polymers but is inherent in PMVE polymers. 

Oppositely charged polyelectrolytes interact with each other to form polyelectrolyte complexes in solution, the possible combinations including strong poly-acids-strong polybases, strong polyadds-weak polybases, weak polyadds-strong polybases, weak polyadds-weak polybases, or polyampholytes. Consid-... 

On the other hand, when integral-type polycations (having cationic charges on the backbone chain) instead of pendant-type polycations, are used as strong polybases, different phenomena are observed. Tsuchida et al.m) discussed the interactions between NaSS and a series of integral-type polycations, called ionenes ... 

Branched polyethylenimine (BPEI) is a strong polybase even at high ionic strength [79, 80] and forms complexes with acids. Its behavior is determined by properties such as the branched structure, presence of three different types of amine groups, strong neighboring interactions between various amine groups, and the compact structure in aqueous solution. 

Figure 2 shows also the relationship between [ii] and pH of MGC and PVSK, a strong polybase and strong polyacid, respectively. Linear curves... 

In solutions, the counterions of poly electrolytes are HjO (for the polyacids) and OH (for the polybases), cations such as K+ and Na, or anions such as Cl (for the polysalts). The addition of polyvalent counterions (such as Ca, Mg, Cu, AT ) produces ionic cross-linking interfering with solubility The polyelectrolyte precipitates and may be redissolved upon addition of a strong acid (such as HCl). This can be regarded as a special case of ion exchange. 

This conclusion is based on a high char yield and similar rates of mass loss at 300°C for untreated and boric acid treated samples. Boric acid samples also had much higher AH+ s and, consequently, higher Ea s. Our results suggest that certain thermally-stable, weak polybasic acids which can complex with polysaccharides may provide fire-resistant properties to lignocellulosics. The results and conclusions were strongly influenced by the technique used to analyze the TGA data. 

A monobasic base is one that will accept just one hydrogen ion per formula. Examples include sodium hydroxide, NaOH, a strong base ammonium hydroxide, NH4OH, a weak base and sodium bicarbonate, NaHC03, a weak base. A polybasic base is one that will accept two or more hydrogen ions per formula. Examples include sodium carbonate, Na2C03, a dibasic base, and sodium phosphate, Na3P04, a tribasic base. 

The percentage of acrylate groups may be adjusted by addition of a strong base, e.g. NaOH. In the presence of polybases such as PEO, PVME and PVP, the following complexation equilibrium takes place ... 

Figure 2 shows that for a polymer couple, even for a large excess of polybase, the fraction of carboxylic groups actually complexed (given by the compelxation degree 0) is always smaller than one and strongly depends on a (or on p, see Figure 3). This corresponds to a variable mean stoichiometry in contradiction with most of the previous papers, where a mean complex stoichiometry close to 1 1 is proposed (5-10). but in agreement with Morawetz s results (16).

The system with very strong interaction between monomer and template was studied by Blumstein at Polybase ionenes were used as templates. A set of ionenes such as... 

The definition of pH is pH = —log[H+] (which will be modified to include activity later). Ka is the equilibrium constant for the dissociation of an acid HA + H20 H30+ + A-. Kb is the base hydrolysis constant for the reaction B + H20 BH+ + OH. When either Ka or Kb is large, the acid or base is said to be strong otherwise, the acid or base is weak. Common strong acids and bases are listed in Table 6-2, which you should memorize. The most common weak acids are carboxylic acids (RC02H), and the most common weak bases are amines (R3N ). Carboxylate anions (RC02) are weak bases, and ammonium ions (R3NH+) are weak acids. Metal cations also are weak acids. For a conjugate acid-base pair in water, Ka- Kb = Kw. For polyprotic acids, we denote the successive acid dissociation constants as Kal, K, K, , or just Aj, K2, A"3, . For polybasic species, we denote successive hydrolysis constants Kbi, Kb2, A"h3, . For a diprotic system, the relations between successive acid and base equilibrium constants are Afa Kb2 — Kw and K.a Kbl = A w. For a triprotic system the relations are A al KM = ATW, K.d2 Kb2 = ATW, and Ka2 Kb, = Kw. 

Drugs may also have more than two pKa values, such as polyprotic or polybasic compounds (e.g., minocycline), and such drugs exhibit a complex pH solubility profile. It is essential to know per se pH of the drug solution during preformulation studies. The pH is measured or theoretically calculated if the pKa and drug concentration C are known. The pH of a weak acid or the salt of a weak base and a strong acid can be calculated using the equation... 

Some papers60-61 have been devoted to phase separation of polyionic complexes from partially furated (PVA-S) and aminoacetylated (PVA-AAC)poly(vinyl alcohol) in aqueous salt solutions. The separation liquid-liquid or complex coacervation occurs at a definite value of the charge density on the macromolecule. From the concentration dependence of the reduced viscosity of the initial components PVA-S, PVA-AAc and their equivalent mixture in water it follows that the viscosity of the components noticeably increases with dilution, and the curve of the equivalent mixture is concentration independent. This fact confirms the formation of the neutral polymer salt, due to electrostatic interactions of PVA-S (strong polyadd) and PVA-AAc (weak polybase). 

A large number of macromolecules complementary to PMAA, namely polyvinylpyrrolidone, polyvinylpyridine, polyacrylamide, poly(vinyl alcohol), poly(ethylene oxide), oligoethylenimine, poly(sodium styrene sulfonate), polycations of the integral type ionen (2X) were used as P2 and P3. The pH of the media strongly influences the studied reactions of complex formation. For example, in PVPy + PVP + PMAA or OEI + PEO + PMAA systems in the add region, where weak polybases are completely protonized and PMAA does practically not dissodate, complexes with hydrogen bonds (PMAA-PVP or PMAA-PEO) are formed. In neutral medium weak polybases are partially ionizated and polyelectrolyte complexes (PMAA-PVPy, PMAA-OEI) are generated. In the alkaline medium formation of complexes has not been observed. 

The ratio of successive ionization constants for a polybasic acid is usually about 10 , as in this case. We see that with respect to its first hydrogen phosphoric acid is a moderately strong acid—considerably stronger than acetic acid. With respect to its second hydrogen it is weak, and to its third very weak. 

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