Polymerization solid-state polycondensation

Figure 5.9 Effect of crystallinity on the solid-state polycondensation of PET, shown as the number-average molecular weight as a function of time. Conditions fluidized bed polymerization at 230°C particle size, 35-48 mesh superficial velocity of nitrogen, 43cm/s [6]. From Chang, T. M., Polym. Eng. Sci., 10, 364 (1970), and reproduced with permission of the Society of Plastics Engineers...

High-molecular-weight polyesters cannot be made by polymerization in the molten state alone - instead, post-polymerization (or polycondensation) is performed in the solid state as chips (usually under vacuum or inert gas) at temperatures somewhat less than the melting point. The solid-state polycondensation of polyesters is covered in detail in Chapters 4 and 5. 

A few cases of prevailing polycondensation. Rec. Trav. Chim. 7,277 (1952). Macchi, E. M., N. MorGsoff, and H. Morawetz Polymerization in the solid state. X. The solid state conversion of 6-aminocaproic acid into oriented nylon 6. J. Polymer Sci., to be publi ed — Morosoff, N., D. Lim, and H. Morawetz Preparation of biaxially oriented polycaproamide by the solid state polycondensation of e-aminocaproic acid. J. Am. Chem. Soc. 86, 3167 (1964). 

It was found meanwhile that nearly every slim unbranched polymer chain, such as poly(trimethylene oxide) [224], poly(l,3-dioxolane) [225], poly(tetramethylene oxide) [226], polyethylene imine) [227], poly(3-hydroxy propionate), poly (4-hydroxybutyrate) and poly(6-hydroxyhexanoate) [228,229], poly(butylene succinate) [229], polyadipates [230], nylon-6 [231], and even oligomers of polyethylene [232], form a-CD ICs with channel structures. In all of these cases, inclusion is a heterogeneous process, since the guest polymer and its CD complex are almost insoluble in water. Therefore, extensive sonication had to be applied to accelerate the diffusion process. The polymer was also dissolved in an organic solvent, e.g., nylon-6 in formic acid, and this solution was added to the solution of a-CD [231], Alternatively, a monomer, such as 11-aminoundecanoic acid, was included in a-CD and polymerized to nylon-11 by solid state polycondensation within the channels of the IC. Thus, the IC of nylon-11 was formed under conservation of the crystal packing [233-235],... 

The concentration of the remaining monomer decreases to zero at 120 and 140 °C where the polymerization systems turn to solid state, whereas at 160 °C the monomer consumption reaches a plateau with the melt-state retained. The same technique is utilized to increase the molecular weight of PLA in the solid-state polycondensation of lactic acid vide infra). 

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). 

Actual polymerizations are carried out in a variety of ways. These can be categorized as homogeneous and heterogeneous systems. Homogeneous systems include bulk and solution polymerization, whereas suspension polymerization, emulsion polymerization, bulk polymerization with precipitate, interfacial polycondensation, and solid-state polycondensation constitute the heterogeneous systems. 

Stereoblock PLA was synthesized by solid-state polycon-densation of a 1 1 mixture of PLLA and PDLA [34]. In the first step, PLLA and PDLA having a medium molecular weight were melt polycondensated. The PLLA and PDLA were then melt blended in a 1 1 weight ratio to allow formation of their stereocomplex, and the blend was subjected to solid-state polycondensation. Some process optimization with regard to polymerization conditions was done and molecular weights exceeding 100.000 g/mol were... 

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... 

Certain polyamides and polyesters can be prepared by solid-state polycondensation step polymerization, usually by heating the appropriate monomer or monomer salt. For example, nylon 11 can be prepared by heating crystals of 11-aminoundecanoic acid (melting point =188 C) at 160°C under vacuum. Polyaddition step polymerization of conjugated dialkene monomers can be induced in the solid state by exposure of the monomer to ultra-violet radiation. For example, irradiation of crystalline 2,5-distyrylpyrazine yields quantitatively a highly crystalline linear cyclobutane polymer... 

Figure 4 shows a comparison of the time dependence curve of the inherent viscosity of the polyimide formed by the microwave-assisted polycondensation of 12PMA with that by a conventional solid-state polycondensation at 250°C. It is obvious that the microwave-assisted polyo)ndensation for curve A proceeded much faster than the solid-state polycondensation for curve B. Thus it is concluded that the internal heating by the microwave irradiation was highly effective compared with a conventional external heating, yielding the polyimide with a high inherent visocisty in a very short polymerization time. 

Flory outlined [3] that the definition of polycondensation is necessarily based on kinetic aspects and not on the structure of polycondensates, because numerous polycondensates can also be prepared by ROP which usually proceeds as chain-growth polymerization. Flory s definition of step-growth polymerization is limited to polycondensations and polyadditions in the melt or in solution, and does not include solid-state polycondensations. Hory s definition of step-growth polymerizations is based on point 1. 

The preparation of PGA given below (Scheme 2.51) is a polycondensation of glycolic acid followed by a solid-state postpolycondensation.374 (Reproduced from ref. 374. Copyright 2000 Elsevier Science Ltd, by permission of the copyright owner.) This method is different from the commonly used ring-opening polymerization of lactide (see Section 2.3.6). 

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],... 

Just as the products of polycondensation are greatly varied, so are the reaction conditions used in their production. Some are produced in the melt (many polyamides and polyesters), some initially in the melt but with extensive polymerization continuing in the solid state (polyurethane foams and elastomers), in solution (some polyurethane fibres) or in non-homogeneous liquid systems (some polycarbonates, very high melting polyamides). 

Polycondensation reactions starting with the monomer in the solid state have been reviewed by Morawetz [13—15). In these polymerizations the monomer is already restricted to a lattice position and the reaction is often influenced by the crystal structure of the monomer (topochemical reaction). Since it is unlikely that polymerization takes place in the interior of a perfect monomer cr5 tal one assumes that the... 

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... 

Polymer Chemical compound consisting of monomers or prepolymers developed by polyaddition, polycondensation or polymerization, usually in solid state. In cured condition, adhesives generally consist of polymers. 

---