Polymerization via

In cationic polymerization the active species is the ion which is formed by the addition of a proton from the initiator system to a monomer. For vinyl monomers the type of substituents which promote this type of polymerization are those which are electron supplying, like alkyl, 1,1-dialkyl, aryl, and alkoxy. Isobutylene and a-methyl styrene are examples of monomers which have been polymerized via cationic intermediates. 

Direct amidation is generally carried out ia the melt, although it can be done ia an iaert solvent starting from the dry salt (46). Because most aUphatic polyamides melt ia the range of 200—300°C and aromatic-containing polyamides at even higher temperatures, the reactants and products must be thermally stable to be polymerized via this method. 

Polymerization via Nucleophilic Substitution Reaction. Halo- and nitro- groups attached to phthahmide groups are strongly activated toward nucleophilic substitution reactions. Thus polyetherimides ate synthesized by the nucleophilic substitution reaction of bishaloimides (59,60) and bisnitroimides (61,62) with anhydrous bisphenol salts in dipolar aptotic solvents. 

Polymerization by Transimidization Reaction. Exchange polymerization via equihbrium reactions is commonly practiced for the preparation of polyesters and polycarbonates. The two-step transimidization polymerization of polyimides was described in an early patent (65). The reaction of pyromellitic diimide with diamines in dipolar solvents resulted in poly(amic amide)s that were thermally converted to the polyimides. High molecular weight polyimides were obtained by employing a more reactive bisimide system (66). The intermediate poly(amic ethylcarboamide) was converted to the polyimide at 240°C. 

Low pressure polymerization via ionic catalysts, using Ziegler catalysts (aluminum alkyls and titanium haUdes). 

Several mechanisms for the polymerization of vinyl ether and epoxies have been suggested [20,22,23,25,27,28,33-35]. On irradiation with gamma rays or electrons, pure epoxies polymerize via a cationic mechanism [35]. However, this cationic polymerization is inhibited by just traces of moisture, as shown below for cyclohexene oxide in reaction 5. 

The furfuryl esters of acrylic and methacrylic acid polymerize via a free-radical mechanism without apparent retardation problems arising from the presence of the furan ring. Early reports on these systems described hard insoluble polymers formed in bulk polymerizations and the cross-linking ability of as little as 2% of furfuryl acrylate in the solution polymerization of methylacrylate121. ... 

The unreactivity of cyclohexene (Section II.A) may be explained by the fact that in this case the ring strain of the dimer is much higher than that of the monomer. The observation that cyclohexene can be a reaction product [Eq. (8)] supports the assumption that thermodynamic rather than kinetic limitations prevent cyclohexene from polymerizing. Calderon and Ofstead (24, 100) have observed that bicyc o-[2.2.2]2-octene can be polymerized via ring opening ... 

Other commercially relevant monomers have also been modeled in this study, including acrylates, styrene, and vinyl chloride.55 Symmetrical a,dienes substituted with the appropriate pendant functional group are polymerized via ADMET and utilized to model ethylene-styrene, ethylene-vinyl chloride, and ethylene-methyl acrylate copolymers. Since these models have perfect microstructure repeat units, they are a useful tool to study the effects of the functionality on the physical properties of these industrially important materials. The polymers produced have molecular weights in the range of 20,000-60,000, well within the range necessary to possess similar properties to commercial high-molecular-weight material. 

Swager et al. prepared conjugated polymers with tethered rotaxane groups [76]. As a substrate, a rotaxane containing a diiodobiphenyl unit was synthesized for this purpose. Polymerization via microwave-assisted Sono-... 

FIGURE 1 Schematic representation of the use of trifunctional amino acids as monomeric starting materials for the synthesis of pseudopoly-(amino acids), (a) Polymerization via the C terminus and the side chain R. (b) Polymerization via the N terminus and the side chain R. (c) Polymerization via the C terminus and the N terminus. The wavy line symbolizes any suitable nonamide bond. See text for details. ... 

Poly(2,6-dimethyl-l,4-oxyphenylene) (poly(phenylene oxide), PPG) is a material widely used as high-performance engineering plastics, thanks to its excellent chemical and physical properties, e.g., a high 7 (ca. 210°C) and mechanically tough property. PPO was first prepared from 2,6-dimethylphenol monomer using a copper/amine catalyst system. 2,6-Dimethylphenol was also polymerized via HRP catalysis to give a polymer exclusively consisting of 1,4-oxyphenylene unit, while small amounts of Mannich-base and 3,5,3, 5 -tetramethyl-4,4 -diphenoquinone units are always contained in the chemically prepared PPO. 

There are many varieties of free radical initiators. Chemical initiators decompose to create radicals examples include organic peroxides, azo compounds, or even oxygen. More rarely we initiate polymerization via a physical condition, such as heat or high energy radiation, to create free radicals directly from the monomers. 

The term catalyst is often misused in anionic polymerization. These mechanisms require the use of initiators that differ from catalysts in that they are not regenerated at the end of the reaction. The similarity between initiators and catalysts is that they both create a situation that permits polymerization via a reduction in the activation energy of the process. 

The vinyl chloride monomer polymerizes via addition polymerization to form polyvinyl chloride. The final polymer has the chemical composition shown in Fig. 22.1. The polymer exhibits limited crystallinity, though this property is not often considered as important in defining its performance. It tends to be atactic or regionally syndiotactic, surrounded by extended atactic runs. When exposed to temperatures above 100 °C, polyvinyl chloride decomposes, creating free radicals that further attack the polymer chain, as we shall discuss in more detail later. For this reason, the degradation of polyvinyl chloride is autocatalytic... 

Carbonyl Groups. Such structures could be introduced by air oxidation during polymerization or subsequent processing of the polymer. There is, in fact, some experimental evidence for their formation during polymerization via the following sequence of steps (6) (1) copolymerization of vinyl chloride with adventi-... 

A chromotrophic acid spot test for formaldehyde (23) was also negative for the polymer ozonolysis solution, while it was positive for a control solution containing formaldehyde equivalent to that expected in the experimental solution if one per cent of the double bonds were vinyl, i.e., polymerization via the internal double bond. 

A carbazole-functionalized norbornene derivative, 5-CN-carbazoyl methy-lene)-2-norbornene, CbzNB, was polymerized via ROMP using the ruthenium catalyst Cl2Ru(CHPh)[P(C6Hii)3]2 [100]. The polymerization was conducted in CH2C12 at room temperature, to afford products with polydispersity indices close to 1.3. Subsequent addition of 5-[(trimethylsiloxy)methylene]-2-norbornene showed a clear shift of the SEC trace of the initial polymer, indicating that a diblock copolymer was efficiently prepared in high yield. 

NMR studies on the alkoxide initiators confirm that all the lactones polymerize via an acyl— oxygen scission, including /3-PL (which, by contrast, opens at the alkyl—oxygen bond with (251)). Monomer coordination and subsequent ring opening may be observed by 111 NMR spectroscopy. Coordination is also observed with 7-BL and 7-VL, although these adducts are stable to insertion and polymerization does not proceed. 

The earliest reported ring-opening polymerizations of functionalized norbornenes were carried out in protic solvents (alcohol, water) using iridium, ruthenium, or osmium salts. Thus, norbornenes substituted with ester (93-95), hydroxy (95), chlorine (96), alkoxy (97), and imide (93) groups have been polymerized via metathesis using noble metal catalysts. 

Tetraethylthiuram disulfide (13) induces St polymerization by the photodissociation of its S-S bond to give the polymer with C-S bonds at both chain ends (15). The C-S bond further acts as a polymeric photoiniferter, resulting in living radical polymerization. Eventually, some di- or monosulfides, as well as 13, were also examined as photoiniferters and were found to induce polymerization via a living radical polymerization mechanism close to the model in Eq. (18), e.g., the polymerization of St with 35 and 36 [76,157]. These disulfides were used for block copolymer synthesis [75,157-161] ... 

In view of the surprising results obtained for the monofunctional maleimide HM/IPDBDVE system in Figure 3 for polymerization in air, an equimolar mixture of CHVE and MPBM [bismaleimide made from maleic anhydride and 2-methyl-l,5-pentanediamine] was polymerized via a mercury lamp source in the absence and presence of air (Figure 7). As might be expected from the earlier results in Figure 3, the difunctional maleimide/divinyl ether system exhibits a remarkably high polymerization rate in the presence of oxygen (air). 

RCM of a diene substrate can be favored over competing polymerization via acyclic diene metathesis (ADMET) by adjusting high dilution conditions. 

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