Polycondensation solid-state thermal

In a typical experiment, a monomer or its salt (2 g) in a polar high boiling solvent (1-2 ml) was irradiated under nitrogen atmosphere. The microwave assisted polycondensation proceeded rapidly and was completed within 5 min (inherent viscosity around 0.5 dL/g) for the polyamide synthesis [68] and within 2 min for the polyimides (inherent viscosity above 0.5 dL/g) [69]. The rate of polycondensation of the salt monomers under various conditions decreased in the following series the microwave induced polycondensation>solid-state thermal polymeriza-tion>high-pressure thermal polycondensation [71]. 

Solid-State Thermal Polycondensation of Salt Monomers... 

Another successful example is the solid-state thermal synthesis of the wholly aromatic polyimide P-ODPM (Tg=410 °C) by the polycondensation of the aromatic salt monomer ODPMA derived from bis(4-aminophenyl) ether and py-romellitic acid (see Eq. 3, R =H). Figure 3 shows the DSC and TG curves of salt monomer ODPMA [27]. 

The salt monomer method was successfully applied to the preparation of the electrically-conducting polyimide-carbon black composites [62]. The composites are prepared as follows An aqueous solution of salt monomer 9PMA was mixed with carbon black, giving a suspension. This was evaporated to dryness under reduced pressure to afford a homogeneously-mixed powder composed of the salt monomer and carbon black. The powder was subjected to solid-state thermal polycondensation in the form of a pellet at 240 °C for 1 h under atmospheric pressure. The semiconducting aliphatic polyimides (P-9PM, Tm=315 °C) having electric conductivity of about 10"6 S/cm was readily obtained by mixing only 1 wt% of carbon black based on the polyimide. 

Polycondensation is a typical method for polyimide syntheses, which need aromatic tetracarboxylic acids and aromatic diamines as monomers. Figure 10.1 shows that the polymerization process goes through two reactions The ring-opening polyaddition of aromatic diamines to aromatic tetracarboxylic dianhydrides in solution at room temperature gives soluble precursor polyamic acids, followed by solid-state thermal cyclodehydration to polyimides. 

The chemistry of the solid-state polycondensation process is the same as that of melt-phase poly condensation. Most important are the transesterification/glycolysis and esterification/hydrolysis reactions, particularly, if the polymer has a high water concentration. Due to the low content of hydroxyl end groups, only minor amounts of DEG are formed and the thermal degradation of polymer chains is insignificant at the low temperatures of the SSP process. 

Chang, T. M., Kinetics of thermally induced solid state polycondensation of poly(ethylene terephthalate), Polym. Eng. Sci. 10, 364-368 (1970). 

Chen, F. C Griskey, R. G. and Beyer, G. H., Thermally induced solid state polycondensation of nylon 66, nylon 6-10 and poly(ethylene terephthalate), AIChEJ., 15, 680-685 (1969). 

Chang, T. M., Kinetics of thermally induced solid state polycondensation of... 

Such approach of the synthesis by solid-state reaction is especially attractive with precursors that present silanol functions. Here again, the supramo-lecular association promoted by these functions combined with their reactivity allows to directly transform by a simple thermal treatment a molecular precursor to a polymeric hybrid material. Liu, et al. have reported on the possibility to polycondense silanols in the solid state [95], and Corriu et al. have obtained the formation of layered materials by condensation of bis-trisilanol precursors [96,97],... 

For example, solid state polycondensation (SSP), a way to increase the molecular weight directly on pellets of solid PET, is the evidence that Sb(III) residual is still active in solid polymer. [25-28] On the contrary less information are available about the effect of Ti(IV) residual on SSP for PBT. It is a matter of fact that in all the studies about thermal and thermooxidation degradation, the effects of the eatalytic system are usually ignored because the catalyst is always present as residual in every PBT sample. It is simply a background effect. 

Du C, Lin SKC, Koutinas A, Wang R, Webb C (2007) Succinic acid production from wheat using a biorefining strategy. Appl Microbiol Biotechnol 76 1263-1270 Fujimaki T (1998) Processability and properties of aliphatic polyesters, BIONOLLE , synthesized by polycondensation reaction. Polym Degrad Stab 59 209-214 Gan ZH, Abe H, Kurokawa H, Doi Y (2001) Solid-state microstructures, thermal properties, and crystallization of biodegradable poly(butylene succinate) (PBS) and its copolyesters. Biomacromolecules 2 605-613... 

Poly(amide)s can be formed by a direct polycondensation with either aromatic or aliphatic dicarboxylic acids. The polymers can be reinforced and thermally stabilized with silicon carbide. These poly(amide)s emit green or blue fluorescence in dilute A-methyl-2-pyrrolidinone solution and in the solid state [77]. 

The polyether-ester polyamic acid imidization process in a solid state under microwave irradiation was studied by Yu et al. [73]. The prepolymer, polyether-ester polyamic acid, was prepared by the polycondensation of poly(tetramethylene ether)glycol di-p-aminobenzoate (Polyamine-650, Polaroid, Co.) and pyromellitic acid dianhydride (PMDA) at room temperature in DMF solution. Later, the prepolymer solution was cast on polytetrafiuoroethylene plates to form 200 pm thin films that were imidized under microwave irradiation in a household microwave oven at 60 °C. The temperature was measured by means of a thermocouple applied to the film surface immediately after the intervals of microwave turn off It was found that microwave irradiation reduced both the reaction temperature and time. For example, during the solid phase thermal polymerization 68.3% polyamic acid was converted to polyimide at 155 °C, while under microwave irradiation 65 % of polyamic acid was reacted at 60 °C within 3 h [73]. 

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