Polymerization, substituted

Multi-component catalyst systems based on palladium compounds and phosphorus compounds show a particularly high activity (35). The high catalytic activity is not deteriorated in the course of polymerization. Substituted norbornene derivates can be used that are otherwise difficult to polymerize. 

The polymeric phosphazenes are treated in chapter (see Polyphosphazenes) A recent monograph covers the chemistry of polyphosphazenes (nomenclature, synthesis of cyclic monomers , ring opening polymerization, condensation polymerization, substitution, polymer properties, and applications more than 1000 literature citations). Other reviews have also been published recently. Sulfur-containing polyphosphazenes have also been described. ... 

Transition metal catalysts are useful for the polymerization of acetylenes. Ti catalysts are known to polymerize acetylene. Catalysts containing group V and VI transition metals (i.e., Nb, Ta, Mo, and W) polymerize substituted acetylenes (3, 4). The group V and VI transition metal catalysts can be classified into three groups (1) chlorides of Nb, Ta, Mo, and W (2) 1 1 mixtures of the metal chlorides with organometallic cocatalysts (e.g.. 

At the present time, only a few side-chain liquid crystal polyphosphazenes have been synthesized and investigated. Opportunities exist to prepare a wide variety of side-chain liquid crystalline polyphosphazenes, based on the polymerization-substitution process outlined in Figure 2. Alternative approaches, such as side chain modification of polyphosphazenes prepared by the thermal decomposition of N-silylphosphoranimines (19), may provide even further options for preparing liquid crystal polyphosphazenes. 

Table 10.6 Potential Radiopaques Polymeric Substituted 2,4,6-Triiodobenzoic Acids...

One of the first examples of Lewis-acid free initiators based on tungsten(VI), W(O-2,6-i-Pr2-C6H3)2Cl2(CH-t-Bu)(OR)2, (R=Et, i-Pr), which allowed the polymerization of substituted NBEs, was reported by J.M. Basset et al. [57]. Additionally, Lewis-acid free W(=C(CH2)4)(OCH2-t-Bu)2Cl2 was reported to effectively polymerize substituted NBEs such as exo-norborn-5-ene-2,3-dicarboxylic anhydride [58, 59[. 

E. Vandenbergh (1) and with the mode of preparation of different active systems, polynuclear structures are clearly a key feature for the design of catalysts able to polymerize substituted oxlranes into very high molecular weight polyethers. In an exploratory approach based on these premises and aimed at the synthesis of well characterized and versatile specie of that type, we have shown indeed (2) that soluble p-oxo-bimetallic trinuclear alkoxides having the general formula RO) m1-0-m2-0-m1 (OR)0 rank cunong the best known... 

Since the steady state is reached soon after polymerization starts, we can assume without significant error that it applies to the whole course of the polymerization. Substituting Rf from Eq. (6.18) into Eq. (6.21) one obtains... 

For rings of all sizes the presence of substituents decreases the thermodynamic feasibility for polymerization. Substitution in the ring tends to... 

C3-symmetrical tripodal ligands have been used to obtain amido complexes of family (86). If chiral substituents are present in the ligand periphery, some stereo discrimination is observed in the reaction with several chiral ketones and aldehydes. On the other hand, such systems can generate early-late heterobimetallics with metal-metal bonds (equation 41). Reaction of (91) with MeNC as well as the heteroallenes CO2, CS2, RNCO and RNCS led to insertion into the polar metal-metal bond. Tris (pyrazolyl) borate see Tris(pyrazolyI)borates) Zr and Hf complexes are other interesting examples of the type (86). In combination with MAO, they give promising results in ethylene and ethylene/hexene polymerizations. Substitution of these sterically crowded ligands allows adjustements of the environment of the active site to the... 

TABLE IX Preparation of Monomeric and Polymeric Substituted 2-Oxazolidones from 1,2-Epoxides and Isocyanates"... 

A special step polymerization involves an acyclic diene methathesis polymerization, ADMET [12]. A diene, CH2=CH(-CH2) -CH=CH2, sets up a condensation equilibrium, evolving ethylene in the presence of an ADMET catalyst and allows polymerization. Substituted dienes can produce precisely branched polymers [13]. 

Metathesis type catalysts can also polymerize substituted acetylenes. This is discussed in Chap. 10. 

In order to overcome issues such as inductive and steric effects in polymerizing substituted monomers, less-reactive substituted monomers can be either copolymerized with unsubstituted monomers or homopolymerized under more controlled conditions. In addition, it is important for the substitution to avoid locations that will impede polymer growth. For example, in the case of aniline, the substitution should only be in the meta and/or ortho positions and in the case of aromatic heterocyclics such as thiophene and pyrrole, substitution should only occur in the p position. ... 

A variety of transition metal catalysts have been found to polymerize substituted acetylenes. Effective catalysts range from Group 3 to Group 10 metals. Activity of catalysts greatly depends on monomer structure therefore, it is quite important to recognize the characteristics of each catalyst. Table 1 lists recent representative examples for the polymerization of substituted acetylenes with various transition metal catalysts, which will help readers to imderstand the general features of catalysts. 

Our current hypothesis is that the butadiyne thermopolymer is structurally related to melt polymerized substituted butadiyne polymers. The absence of substituent groups allowed us to make a direct observation of the gradual decrease in triple bond concentration with increasing temperature of heat treatment. This is consistent with the conversion of a polyene to a polyacene structure, although it does not exclude the polyphenyl structure. The presence of an aliphatic C-H band at 2935 cm and its intensity increase with heat eatment is paralleled by the poly(diphenyldiacetylene) system. There is an oxygen uptake (4% 0) on exposure to air and a strong ESR signal both of which e also characteristic of the poly(diphenyldiacetylene) system. These observations are not understood at this time. 

Since the 1950s, other catalysts have been used to polymerize substituted acetylenes [25]. Free radical initiators (e.g., benzoyl peroxide, di-f-butylperoxide) are active catalysts, as are complexes of other transition metals like Ni and Co. Recently, both Rh and Pd cationic complexes have been shown to polymerize monosubstituted acetylenes [119-121]. Thermal polymerizations and y-... 

Bilayer structures have been prepared and investigated with various spectroelectrochemical techniques [307, 486]. In the former report, surface resonance Raman spectroscopy showed typical vibrational features of the involved polymers [PANI and poly(o-phenylenediamine] as already discussed were observed. In the latter investigation, involving PANI/poly(5-chlorine,2-metho3 ani-line), it was concluded that the topmost layer of the polymerized substituted aniline blocks the electrochemical reduction of the inner layer of PANI. This was first deduced from the diminished height of reduction peaks in the CV. Moreover, this was supported by in situ UV-vis spectra that showed typictil bands of oxidized PANI even after formal reduction of the film. 

The charge generation and retention properties of polymers also depend very much on their chemical structure as well as their physical nature, which limit t ir accessibility beyond a certain range. It is possible to modify the properties of polymers by doping, co-polymerization, substitution, or by blending two or more polymers together. These properties, in turn, affect the dielectric and charge formation characteristics which are determined by intra- and intcrmolecular interactions. 

McLain et polymerized cyclopentene by late transition metal catalysts using MAO and borate-activated nickel and palladium diimine complexes. The nickel diimine complexes produce crystalline materials showing a ds-1,3 enchainment with a melting point of 240-330 °C. The hydroligomers were mainly atactic. Palladium catalysts gave pure atactic polymers. It is also possible to polymerize substituted cyclopentenes such as 3-methyl- or 3-ethyl-cyclopentene. 

Chem. Descrip. Sodium salt of polymerized substituted arylalkyl sulfonic adds combined with an inert inorg. suspending agent Uses Dispersant for latex processing... 

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