Polymers polycondensation

Polyimides (PI) are polycondensation products (1) prepared from derivatives of tetracarboxylic acids and primary diamines (1—5). Descriptions of self-polycondensation polymers (2) based on aminodicarboxylic acid derivatives are also found in the literature (6—9). 

Later, Kricheldorf and coworkers [93,94] extensively demonstrated the use of 0-silylated bifunctional monomers, such as diphenols, for synthesis of a wide variety of polycondensation polymers. The silylated oxygen of difunctional phenols may be condensed with activated... 

Recently, various polyesters such as poly(ethylene adipate), poly(tetramethylene adipate), poly(caprolac-tone), and poly(aliphatic carbonate), having terminal hydroxyl groups, were reacted with ACPC to give corresponding macroazoesters and their thermal behaviors were observed by DSC [14]. The block copolymers of these polycondensation polymers with addition polymers such as PSt and PMMA were synthesized [14]. 

Realizing a wide range of selection of composing members including vinyl polymers, polycondensation polymers, and polyaddition polymers, which opens a variety of application areas in the polymer manufacturing and processing industries. 

Wittig-Type and Wittig-Horner-Type Polycondensations Polymers... 

The microheterogeneity coefficient was introduced only for the description of the microstructure of binary copolymers with symmetric units. At increased number of unit types and/or when account is taken of structural isomerism, the role of Km will be performed by other parameters analogous to it. A general strategy for the choice of these latter has been elaborated in detail [12], while their values have been measured via NMR spectroscopic techniques for a variety of polycondensation polymers [13]. 

PET is a polycondensation polymer based on the reaction of terephthalic acid (TA) and mono-ethylene glycol (MEG) or alternatively with di-methyl terephtha-late (DMT) plus MEG (Figure 10). 

PTT, with three methylene units in its glycol moiety, is called an odd-numbered polyester. It is often compared to the even-numbered polyesters such as PET and PBT for the odd-even effect on their properties. Although this effect is well established for many polycondensation polymers such as polyamides, where the number of methylene units in the chemical structures determines the extent of hydrogen bonding between neighboring chains and thus their polymer properties, neighboring chain interactions in polyesters are weak dispersive, dipole interactions. We have found that many PET, PTT and PBT properties do not follow the odd-even effect. While the PTT heat of fusion and glass transition temperature have values between those of PET and PBT, properties such as modulus... 

Polycondensation polymers such as PET are characterized by low melt viscosities and low melt strengths. Furthermore, with PET there is a marked shear liquefaction... 

When polymerizing A2B monomers there is a possibihty of losing the unique focal point due to intramolecular cyclization. The loss of the focal point in a hyperbranched polyester based on 4,4-(4 -hydroxyphenyl)pentanoic (Fig. 7) acid was closely examined by Hawker et al. [45]. The study showed no significant occurrence of intramolecular cyclization. One disadvantage of polycondensation polymers is that they are sensitive to hydrolysis, that is depolymerization, which might restrict their use. Some hyperbranched polymers are synthesized via substitution reactions which provide less hydrolytically unstable polymers. 

It is important to note that the rate constant k for reactions of similar monofunctional compounds is essentially the same as for the difunctional compounds used in the formation of polycondensation polymers. Likewise, as in the case of reactions of small molecules, the rate constant k increases with temperature in accordance with the Arrhenius equation ... 

Fig. 5. Polycondensation reactions leading to typical polycondensation polymers a PET and b PA6,6...

Table VII gives the Tg values of some polycondensation polymers, polyesters, and polyamides which we have synthesized.

Symmetry. The influence which the geometrical and optical symmetry of the building units of polycondensation polymers exert on the structure of the macromolecules and the properties of the materials has been explored very little, and there are no studies available in our case. However, the diamine (TMD) used has an asymmetric structure and in addition an asymmetric carbon atom. 

Bifunctional acid chlorides and diamines can react in a single oi anic phase to form polyamides. The term solution poly condensation is used to describe two major processes that differ in their product, though the reactions probably follow similar mechanisms. In one group of polycondensations, polymer is precipitated as it forms or as it achieves a range of... 

Chul-Yung Cha The molecular weight distribution of poly (ethylene tereph-thalate) from solid state polycondensation. Polymer Preprints, Am. Chem. Soc. Polymer Div. 6, 84 (1965). 

T T omogeneous catalysis is of major importance in polymer chemistry - - and technology—e.g., in producing vinyl polymers, polydienes, and polycondensation polymers. It permits precise control of all reactants, usually eliminates the necessity of removing catalyst residues from the product, and allows the use of relatively simple apparatus. On the other hand, polymerizations in homogeneous media, especially bulk polymerizations of vinyl monomers, are sometimes so vigorous that proper heat removal may not be eflFected on a large scale. This drawback has limited some of the possible industrial applications (34). 

The discussion concerning polycondensation polymers so far has been restricted to systems using only bifunctional monomers. By doing this we have seen that high purity, very close to equimolar (stoichiometric) proportions of functional groups, and nearly complete reactions are needed to obtain useful high molecular weight material. The linear products from these types of polymerizations may be more or less readily melted, or dissolved in a solvent for production of useful fibers, shapes, etc., from the crude polymer resins. 

The configurations of the glycosidic bond in natural polycondensed polymers of sialic acid are a-(2—>8) and a-(2- 9). Exceptionally, in the polysialic acid of starfish, the interglycosidic bond involves the primary alcohol function of the... 

A wide variety of A2B monomers, such as 2,2-dimethyl propionic acid, 3,5-diacetoxybenzoic acid, 3,5-6is(trimethylsiloxy)benzoyl chloride, 3,5-dihydroxy-benzoic acid, and 5-acetoxyisophthalic acid have been used for the synthesis of hyperbranched polymers. A majority of the polymers are synthesized via step-wise polymerizations where A B monomers are bulk-polymerized in the presence of a suitable catalyst, typically an acid or a transesterification agent. To achieve satisfactory conversion, the low-molecular-weighf condensation product (e.g. H2O, CH3OH) formed during the reaction has to be removed. This is most often accomplished by passing an inert gas or by reducing the pressure in the reaction vessel. A drawback of polycondensation polymers is that they are prone to depolymerization by hydrolysis, which might restrict their use. 

In fact, Bayer invented a new method for the synthesis of macromolecular compounds the polyaddition reaction, which is a special case of polycondensation, with the difference that the reaction product is exclusively the polymer. In the classical polycondensation reactions, the products are the polycondensation polymer and a low molecular weight (MW) compound (water, alcohols, and so on). The fact that in the polyaddition reactions... 

---