Catalyst solid-state polycondensation

The papers of Mallon and Ray [98, 123] can be regarded as the state of the art in understanding and modelling solid-state polycondensation. They assumed that chain ends, catalysts and by-products exist solely in the amorphous phase of the polymer. Because of the very low mobility of functional groups in the crystalline phase, the chemical reactions are modelled as occurring only in the amorphous phase. Additionally, the diffusion of by-products is hindered by the presence of crystallites. The diffusivity of small molecules was assumed to be proportional to the amorphous fraction. Figure 2.32 shows the diffusion coefficients for the diffusion of EG and water in solid PET. 

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. 

Duh B. Effect of antimony catalyst on solid-state polycondensation of poly (ethylene tere-phthalate). Polymer 2002 43 3147-3154. 

Oxidative Poiymerization of Naphthoi Derivatives. Oxidative polymerization of 2-naphtol (109) and 1,5-dihydroxynaphthalene (110) has been done using enzyme catalysts. Solid-state polycondensation of 2,6-dihydroxynaphthalene with FeCls catalyst (111) has been accomplished. Asymmetric oxidative coupling polymerization of 2,3-dihydroxynaphthalenes and their derivatives was achieved by chiral copper catalysts (112-115). 

Moreover, the molecular weight remained around 100 000 Da, being much lower than that of the PLLA obtained by the ring-opening polymerization of Z-lactide. Therefore, they examined the melt/solid polycondensation of lactic acid in which the melt polycondensation of Z,-lactic acid was subjected to solid-state polycondensation below Tm of PLLA [8]. In solid state, the polymerization reaction can be favored over the depolymerization or other side reactions. Particularly, in the process of crystallization of the resultant polymer, both monomer and catalyst can be segregated and concentrated in the noncrystalline part to allow the polymer formation to reach 100% [9]. Figure 3.2 shows the whole process of this melt/solid polycondensation of Z-lactic acid. In this process, a polycondensation with a molecular weight of 20 000 Da is first prepared by... 

According to the principles of polycondensation, all of the above reactions will also take place during SSP. The conditions for the latter, however, are different as this process is carried out at lower temperatures in a non-homogeneous environment. In order to examine the kinetics of SSP, some assumptions have to be made to simplify the analysis. These are based on the idea that the reactive end groups and the catalyst are located in the amorphous regions. Polycondensations in the solid state are equilibrium reactions but are complicated by the two-phase character of the semicrystalline polymer. 

Such polycondensation dehalogenation reactions remain a commonly employed route to poly thiophene, and a range of solvents, halogenothiophene substrates, and other metal-based catalysts have been examined, as recently reviewed.29 For example, the reaction of 2,5-dibromothiophene with Ni(cyclooctadiene)2 and triphenylphosphine in DMF leads to an almost quantitative yield of polythiophene.30 Solid-state 13C NMR studies confirm exclusive 2,5-coupling of the thiophene repeat units in the polymeric product. The 2,5-dichlorothiophene monomer is less active as a substrate in such reactions however, the corresponding 2,5-diiodothiophene is reported to be a good substrate.31... 

Kim et al. [19] fabricated PET/clay composites using a two-step in-situ polymerization method. In the first step, a slurry mixture of monomer (purified tereph-thalic acid and ethylene glycol), polycondensation catalyst, clays, and some additives was kept at 250 °C for 5-6h in the esterification step. Then, it was transferred to a polycondensation reactor until the intrinsic viscosity (IV) value reached 0.6dlg" . Then, the materials were pelletized. Furthermore, a solid-state polymerization (SSP) process is carried out to conduct the polymerization process further. SSP was carried out at between 220 and 145 °C for around 8h until the IV reached 0.8dlg . ... 

Hydroxyl-functionalized cinnamic acid derivatives such as p-coumaric acid (p-hydroxycinnamic acid), ferulic acid, and sinapinic acid are attractive monomers for syntheses of high-performance polyesters. The obtained polyesters are also expected to be biodegradable in the case of copolymerization with aliphatic hydroxy acids such as lactic acid. Tanaka et al reported the thermal polycondensation of p-coumaric acid at 550 °C without any catalyst under high pressure up to 80 kbar (in the solid state) in 1975. They obtained red or brownish-red hard solids insoluble in conventional organic solvents. Higashi and his co-workers synthesized copolyesters of p-coumaric acid and 4-hydroxybenzoic acid or their methoxy substitutions (ferulic acid, vanillic acid, or syringic acid) by polycondensation using hexachlorocyclotri(phosphazene) in pyridine in 1981. The obtained polymers that exhibited UV spectra different... 

The study of the optical properties of thin films revealed that the hydrolysis-polycondensation process resulted in a modification of the supramolecular organization of Si(OEt)3-lmPV in the solid state. Si(OEt)3-lmPV was hydrolyzed and polycondensed using tetrabutylammonium fluoride (TBAE) as a catalyst. The films obtained by the sol-gel process using the TBAE are designated by Si (OEt)3-lmPV-E. 

---