Various Polycondensates

CBZ-PMDA), carbazole-1,4,5,8-naphthalene tetracar-boxylic dianhydride (CBZ-NTDA) and carbazole-benzophenone tetracarboxyl dianhydride (CBZ-BTDA) were synthesized by a similar method. Poly(N-vinyl-carbazole)-anhydride co-polycondensates such as PNVC-PhAn, PNVC-TMA, PNVC-PMDA, PNVC-NTDA and PNVC-BTDA were also prepared. Thermal stability characteristics of the various polycondensates have been compared in Table 16.18 and it was observed that (i) the initial decomposition temperature and the overall stability of a co-polycondensate of either CBZ or PNVC depends upon the anhydride moiety in the order of NDTA > BTDA > PMDA >TMA > PhAn (ii) initial decomposition temperature and the overall stability of a co-polycondensate with a fixed anhydride, vary in the order PNVC > CBZ and (iii) polycondensation of PNVC by anhydrides improves the thermal stability of the base polymer. It is suggested that the incorporation of thermally stable moieties, cross-links and rigidity is the main reason for enhanced initial decomposition temperature as well as overall thermal stability of these co-polycondensates. Table 16.19 gives the isothermal degradation stability of pairs of polycondensates and data confirm the high thermal stability... 

Table 17-1. Equilibrium Constants of Various Polycondensations. The Examples 6 and 7 Refer to the First Stage of the Polycondensation to Polyamidic Acids Which Proceeds without Water Elimination...

Table 17-5. Rate Constants of Various Polycondensations. The Phenyl Groups Are Always Substituted in the Para Position...

These reactions are independent of the metakaolin used except in the case of the geopolymer Ml where the presence of several networks has been highlighted. These different networks imply various polycondensation mechanisms, which explains the differences observed between this sample and the other materials. 

The silanols formed above are unstable and under dehydration. On polycondensation, they give polysiloxanes (or silicones) which are characterized by their three-dimensional branched-chain structure. Various organic groups introduced within the polysiloxane chain impart certain characteristics and properties to these resins. 

Various inorganic, organic, and organometaUic compounds are known to cataly2e this polymerization (4,8,9). Among these, BCl is a very effective catalyst, although proprietary catalysts that signiftcandy lower polymerization temperature from the usual, sealed-tube reaction at 250°C are involved in the industrial manufacture of the polymer. A polycondensation process has also been developed for the synthesis of (4) (10—12). This involves elimination of phosphoryl chloride from a monomer prepared from (NH 2 04 and PCl. ... 

Table 2. Glass-Transition Temperatures of Polysulfones Produced from the Polycondensation of Dichlorodiphenylsulfone with Various Bisphenols ...

To incorporate a labile azo group as the essential active site to MAI, a series of azo compounds such as 2,2 azobisisobutyronitrile (AIBN), 4,4 -azobis(4-cyanopen-tanoyl chloride) (ACPC), 2,2 azobis (2-cyanopropanol) (ACPO), 2,2 azobis [2-methyl-N-(2-hydroxyethyl)prop-ionamide] (AHPA), etc., were used as starting materials for polycondensation with various diols, diamines, diacids, or diisocyanates. 

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]. 

In this chapter we summarize the various methods of calculation which are reported in the literature, we show that when the polycondensation is stoichiometric no correction is needed and we propose new relations for cases where the balance between reactive groups is non-stoichiometric. 

Tough, transparent, heat and flame resistant, multiblock (bisphenol fluorenone carbonate) (BPF)-dimethylsiloxane copolymers have been synthesized by interfacial polycondensation of phosgene with various mixtures of BPF end-capped siloxane oligomers and free BPF or its monosodium salt 232). Siloxane content of the copolymers were varied between 7 and 27%. Presence of two Tg s, one below —100 °C and the other as high as 275 °C, showed the formation of two-phase morphologies. 

Tetraene 141 has been converted into various complex polycondensed adducts by reacting with a variety of dienophiles such as maleic anhydride, N-phenylmaleimide, N-phenyltriazolinedione,p-benzoquinone and tetracyano-ethylene carried out under thermal conditions. All cycloadditions occurred facial-diastereoselectively from an outside attack and provided monocycloadducts which had an exceptionally close relationship between diene and dieno-phile and then underwent intramolecular cycloaddition [125]. The reaction between 141 and p-benzoquinone is illustrated in Scheme 2.53. 

Example 13.1 Determine the stoichiometric requirements for achieving various degrees of polymerization for a binary polycondensation. 

In a seminal and seemingly forgotten paper, Burchard et al. " discussed the analysis of various polymer architectures based on integrated light scattering (LS) and quasielastic light scattering (QELS). They considered mono- and polydisperse linear and star-branched polymers with/number of arms ( rays ), and random polycondensates of Af or ABC type (identical or different... 

Imidazolides of adenylic acid (ImpA) or uridylic acid (ImpU) are polycondensed to oligonucleotides by means of Zn2+ ions. 1673 The resulting phosphordiester bond was found to be of the 2, 5 type. In the reaction of nucleoside 5 -phosphoric acid methyl ester with ImpA in the presence of MgC, 2, 5 -dinucleotides are formed six to nine times more frequently than the corresponding 3, 5 compounds. 63 Polycondensations of ImpA in aqueous solution in the presence of various divalent metal ions lead to short oligo-adenylic acids (pA) (n = 1—5) mainly with 2, 5 -intemucleotide linkages. With Pb2+, for example, the total yield of oligomers was as high as 57%. 1683 1693... 

Various molecular borylaminoborazinic derivatives of this type can be prepared by the synthetic pathway depicted earlier. Their polycondensation was realized and... 

When discussing various methods for the synthesis of protein-like HP-copolymers from the monomeric precursors (Sect. 2.1), we pointed to the possibility of implementation of both polymerization and polycondensation processes. The studies of the potentials of the latter approach in the creation of protein-like macromolecular systems have already been started. The first published results show that using true selected reactions of the polycondensation type and appropriate synthetic conditions (structure and reactivity of comonomers, solvent, temperature, reagent concentration and comonomer ratio, the order of the reagents introduction into the feed, etc.) one has a chance to produce the polymer chains with a desirable set of monomer sequences. 

Aromatic polycarbonates are currently manufactured either by the interfacial polycondensation of the sodium salt of diphenols such as bisphenol A with phosgene (Reaction 1, Scheme 22) or by transesterification of diphenyl carbonate (DPC) with diphenols in the presence of homogeneous catalysts (Reaction 2, Scheme 22). DPC is made by the oxidative carbonylation of dimethyl carbonate. If DPC can be made from cyclic carbonates by transesterification with solid catalysts, then an environmentally friendlier route to polycarbonates using C02 (instead of COCl2/CO) can be established. Transesterifications are catalyzed by a variety of materials K2C03, KOH, Mg-containing smectites, and oxides supported on silica (250). Recently, Ma et al. (251) reported the transesterification of dimethyl oxalate with phenol catalyzed by Sn-TS-1 samples calcined at various temperatures. The activity was related to the weak Lewis acidity of Sn-TS-1 (251). 

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