Solid state thermal polymerization

Differential thermal analysis of the mixed-metal complex, cis-[Pt(SCN)(SCNAg)(NH3)2l[N03], which contains formally unsaturated silver(I), reveals an exothermic peak at 134-144 The process occurs 

When an acetone solution of the monomeric complex, [NiBr2(P(C2H4CN)3)2]/ was allowed to polymerize at various temperatures, the blue polymeric compound was always contaminated with an unidentified green sutetance. However, when the dry solid was allowed to polymerize at temperatures below 130 °C only the blue material was formed. 3 

These examples illustrate the conditions typically necessary for polymerization, i. e. coordinative unsaturation of the metal center along with the p otential for bidentate or polydentate coordination of the ligands. 

5 Syntheses that involve deprotonation of a coordinated ligand followed by ring-dosure 

The palladium(II) and platinum(Il) complexes of oxyquinoline, IMCl2(OxH)2], where the oxyquinoline ligands (OxH) are coordinated through nitrogen, are transformed into chelate complexes on heating in the solid state,44 Eq. 12.15  

---

The cyclic dimer was completely converted within 10 min at 300 °C, whereas in the case of the trimer a small part remained unpolymerized even after 30 min at 300 °C. The tetramer exhibits an even lower reactivity. Such lower reactivity is due to a slower initiation of the larger ring monomers. At this point, it should be noted that a mixture of cyclic monomers polymerizes much more rapidly than pure cyclic trimers or tetramers. Solid-state thermal polymerization produces a high-molecular-weight polymer (M > 10 ). Cyclic carbonates derived from o,o -bisphe-nols 43-49 and of cyclic carbonates derived from p,p -bisphenols, such as biphenol-A (50), were polymerized and copolymerized in solution using potassium naphthalene, potassium tert-butoxide or phenyl trimethylsilylether in combination with tris (dimethylamino)sulfonium trimethylsilyldifluoride as initiator [7]. From a practical viewpoint, these polycarbonates, which have high heat-deformation temperatures, may be used for moldings [85]. 

Solid-state (topochemical) polymerization of cyclic disulfur dinitride to poly(sulfur nitride) (or polythiazyl), -fSN, occurs on standing at ambient temperature or higher [Banister and Gorrell, 1998 Labes et al., 1979 Ray, 1978]. Disulfur dinitride is obtained by sublimation of tetrasulfur tetranitride. Polythiazyl is a potentially useful material, since it behaves like a metal. It has an electrical conductivity at room temperature about the same order of magnitude as a metal like mercury and is a superconductor at 0.3°C. Polythiazyl also has high light reflectivity and good thermal conductivity. However, it is insoluble and infusible, which prevents its practical utilization. 

The solid state thermal elimination reaction is a very important step in the formation of the final PPV or PPV derivative. In situ infrared spectroscopy therefore plays a critical role in the ability to monitor the reaction that converts the precursor polymer to the final product. We have characterized the mechanism of this conversion reaction in the formation of PPV synthesized by both the sulfonium precursor route (SPR) and the xanthate precursor route (XPR). The polymerization reaction of PPV from the tetrahydrothiophenium monomer is shown in Figure 1. After polymerization of the precursor polymer, the material is thermally converted to the final PPV product. This SPR method involves the thermal elimination of the tetrahydrothiophenium (THT) group and HCl as shown. 

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 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]. 

Some transitions that are only known for macromolecules, however, will not be mentioned at all since they are covered elsewhere in this Encyclopedia (see, eg. Gel Point). Also we shall not be concerned here with the transformations from the molten state to the solid state of polymeric materials, since this is the subject of separate treatments (see Crystallization Kinetics Glass Transition Viscoelasticity). Unlike other materials, polymers in the solid state rarely reach full thermal equilibrium. Of course, all amorphous materials can be considered as frozen fluids (see Glass Transition) Rather perfect crystals exist for metals, oxides, semiconductors etc, whereas polymers typically are semicrystalline, where amorphous regions alternate with crystalline lamellae, and the detailed structure and properties are history-dependent (see Semicrystalline Polymers). Such out-of-equilibrium aspects are out of the scope of the present article, which rather emphasizes general facts of the statistical thermodynamics (qv) of phase transitions and their applications to polymers in fluid phases. 

Several groups were attracted by the mechanistic aspects of asymmetric synthesis from pro-chiral monomers, or the selective polymerization of one enantiomeric form of a racemic mixture, and the corresponding catalytic systems. Increased solid state thermal stability was expected from asymmetry but better interpretation of the properties of biological molecules by studying more simple synthetic models is surely one of the most frequent motivations in the field. 

Marvel et al. described [41] the polymerization of 5,6-dibromocyclohexa-1,3-diene (16) to poly(5,6-dibromo-l,4-cyclohcx-2-ene) 17 followed by a thermally induced, solid state elimination of HBr on the formation of PPP 1. The products, however, display some indications for several types of structural defects (incomplete cyclization, crosslinking). 

Lithium hexafluorophosphate is thermally unstable in the solid state [52], where it decomposes at about 30 °C [53], In solvents and solvates it is more stable. Decomposition begins in the range from 80 °C [53] to about 130 °C [13], yielding scarcely soluble LiF and the Lewis acid PF5 which in turn initiates polymerization of cyclic... 

AgPh is a colourless solid [144] that is rather insoluble in non-donor solvents and appears to be polymeric (AgPh) (n > 10) in addition mixed compounds (AgPh) .AgN03 (n = 2,5) can also be obtained that involve silver clusters. Mesitylsilver is a thermally stable (but light-sensitive) white crystalline solid in the solid state it is tetrameric (in contrast to the pentameric copper and gold analogues) ... 

Consider alternative polymerization processes in solid state, inducing the polymerization reaction of N3P3CI6 thermally [40-42],photochemically [61, 67,68],y-radiolytically [66,210], using X-rays [74,75,90] or electron irra-... 

In the present work, we use quantitative solid-state 13C NMR spectroscopy to study the polymerization process of multiacrylates and the effects of thermal history/aging on the free radical life in polymultiacrylates. 

---