Polymerization of crystalline

Radiation-induced polymerization of crystalline tetroxocane gives a highly crystalline linear polymer in essentially 100% yield (63MI51900,68MI51901), and this has attracted some industrial attention. Tetroxocane also gives a crystalline polymer very rapidly under cationic conditions (boron trifluoride etherate catalyst) and the kinetics of the process have been studied <76MI51900>. 

S2N2 dimerizes rapidly to S4N4 in the presence of nucleophiles and this process can be understood in terms of the frontier orbital interactions between the singly occupied molecular orbital (SOMO) of an S2N2 radical anion and the LUMO of an S2N2 molecule. The polymerization of crystalline S2N2 is a nondiffusive process that produces a mixture of monoclinic (90%) and orthorhombic (10%) (SN). ... 

Polymerization of crystalline methacrylic acid initiated by ultra-... 

The polymerization of crystalline monomers needs a special mention because a larger effort has been expended in this field (75—75). The survey of the studied reactions has produced three major cat ories polycondensations, free radiacal pol5nnerizations, and ring opening polymerizations. 

It is important to recognize that in such cases the rate law of polymerization as obtained by determination of the polymer yield reflects the growth of morphological entities rather then the formation of molecular intermediates and may be determined by the rate of nucleation and by the rate of diffusion of the monomer molecules across the interphase between monomer and polymer lattice. This is well established in the somewhat related case of radiation-induced polymerization of crystalline trioxane (27, 28). 

The trialkyls of Ga, In and T1 resemble those of aluminum but they have been less extensively investigated and are increasingly less stable. One signal point of difference is the lack of dimerization of the alkyls of B, Ga, In and T1 at ordinary temperatures, with the exception of the unusual polymerization of crystalline Me3In and Me3Tl (see page 306). 

In the solid state polymerization of crystalline PEN, the temperature employed ranges from 240°C to about 265°C. As the solid state polymerization of PEN prepolymer proceeds, its sticking temperature increases. Thus, the solid state polymerization temperature can be gradually increased in the course of the process. ... 

POLYMERIZATION CONDITIONS Free-radical polymerizations of acrylamide in aqueous solutions and solid-state polymerization of crystalline acrylamide with ionizing radiation. 

POLYMERIZATION OF CRYSTALLINE TETRAOXANE TO HIGHLY CRYSTALLINE POLY/OXYMETHYLENE/. HEAT CAPACITIES OF MONOMER AND POLYMER AND HEAT OF POLYMERIZATION. 

A rapid high-temperature solid state polymerization of crystalline thermoplastic polymers may be done under conditions of mechanically induced surface stress and friction applied to polymer particles at the incipient melt point temperatures [20]. 

Table 21-3. Maximum Yields in the Polymerization of Crystalline Monomers...

Most cases of radiation-induced polymerizations of crystalline monomers lead to atactic, noncrystallizable polymers. This occurs because of the density difference between the polymer and monomer crystal, which does not allow the monomer enough mobility to orientate sufficiently during the propagation step to produce a stereoregular polymer. 

Polymerization of crystalline monomer, usually vinyl, using high energy radiation. Topochemical, topotactic, and canal polymers belong to this group. 

Solid-state polymerization of crystalline monomer without any intermediate loss of order. The topotactic oligomers have been produced, but the order is lost as the polymerization progresses beyond a low degree of polymerization. Test equipment used for determining the dynamic mechanical properties of plastics. 

These characteristics can be derived from a polymerization of crystalline monomers controlled topochemically. Topotactic reaction geno-ally involve a strong correspondence between the lattices of the monomer crystal and the resulting polymer crystal. Hence, the topochemical solid state reaction occurs when sufficiently intense thermal mobility of molecules takes place in the lattice, and the distance between active centers for the polymerization in the neighboring molecules should not exceed 3.7 A for C — O interactions All monomers mentioned above show quite close C — O interactions. 

Bamford et al. showed that the solid state polymerization of crystalline methacrylic acid (MAA) can be initiated by UV irradiation below 250 nm, instead of y-ray. Polymerization hardly occurred below —20 °C, but radical formation below —20 °C... 

The polymerization of trioxane in the crystalline state is a well-known example of radiation-induced solid-state polymerization In the polymerization of crystalline monomers, the topotactical conditions are very important and polymerization is possible only for a very few monomers. The situation is completely different for... 

Bruk et al. [716] described the low-temperature radiation polymerization of crystalline TFE in detail. It has been established that three solid-phase postpolymerization reactions can take place when irradiated specimens are heated above the melting point low-temperature polymerization (in the interval 77 to IlOK), slow polymerization close to the melting point (in the interval 128 to 138 K), and rapid polymerization during melting of the crystal (142 K). Tabata et al. [717] have found that a significant post-polymerization takes place even in the liquid phase. Kinetic analysis has been made of the in-source and post-polymerizations [718,719]. Post-polymerization is explained by a long lifetime of polymer radicals in the hquid phase at —78 °C due to the slow combination rate of the polymer radicals caused by their rod-like shape. 

Bulk polymerization can be divided into two types polymerization in the solid phase and in the molten phase. Bulk polymerization is interesting for the following reasons (1) polymerization of crystalline monomer may lead to crystalline and stereoregular polymers, and (2) impurities, such as solvent, catalyst, and initiator, may be avoided. However, only the second reason is realistic since polymer obtained by solid-state polymerization is amorphous and shows no tendency to crystallize. The crystalline matrix is unable to exert any appreciable steric control. Further investigations have shown that propagation takes place at the polymer-monomer interface, controlled by local strains and defects in the crystal. Polymerization in the molten monomer soon becomes heterogeneous because of insolubility of polymer in its own monomer. 

The polymerization of crystalline acrylic acid or methacrylic acid at a temperature only slightly below their respective melting points with ultraviolet radiation gave rise to noncrystalline and disoriented polymers. While under these reaction conditions the solid methacrylic acid contained measurable concentrations of free radicals, acrylic acid contained no detectable free radicals. The formation of free radicals in methacrylic acid was found to be very temperature-dependent. As the temperature was lowered, the concentration of free radicals decreased. 

Mechanico-chemical initiation of the polymerization of crystalline salts of acrylic acid [117]. 

The polymerization of o,o-dlacetylenediphenyl glutarate and 5,7-dodecadiinediol-l,12 bis-phenylurethane. (b) The cyclization reaction of N-(para-chlorophenyl) phthalanilic acid to N-(para-chlorophenyl) phthalimidle with the elimination of water. (c) The polymerization of crystalline methacrylic acid. Finally a discussion will be undertaken of the polymerization of molecular multilayers of a number of monomers, such as vinyl stearates and a-octadecylacrylic acid, which may not fit conveniently into any of the above categories. 

The two phases are not clearly observed simultaniously. Thus there is an analogy to the previously discussed polymerization of diacetylene monomers. However, there is no evidence for stereoregularity in these polymers and thus backbone participation in these solid solutions. In fact, no polymer stereoregularity was observed in the analogous bulk polymerization of crystalline vinyl stearate (13). Thus while the side chains anchor the polymerization, the backbone apparently does not crystallize. 

Polymerization of crystalline monomer II, to obtain polymer B, requires a considerably higher optimum polymerization temperature (170°C) than monomer I. Polymer B, poly[oxytetramethylene-thlo(3,5-dlchloro-l,4-phen lene)], generally has a higher number average molecular weight (M ) than polymer A. Unlike monomer I, the polymerization of II Is very dependent upon purity. A series of nucleophiles were Incorporated Into samples of recrystalllzed monomer II and then polymerized ( ). Table I (16) Illustrates the effect of additives upon the specific viscosity (r sp) In chlorobenzene of the resulting polymers. It Is evident that most... 

---