Linear polymers, substituted

Pyrolysis products from organometallic phosphazenes can give nano-structured materials. Mixtures of AuCllPPhs) and poly[2,2 -dioxy-l,l -biphenylphosphazene] were pyrolyzed by heating the sample at 10 °C/min. to 800 °C, which was held for 2 hours under a flow of air. Characterization of the products by X-ray diffraction revealed a nanostructured Au material. Additional experiments were performed with metal centers directed bound to the phosphazene substrate. Structure (43) shows a phosphazene linear polymer substituted with 2,2 -biphenol and 4-hydroxyphenylacetonitrile pendant groups, with ruthenium coordinated to the terminal cyano groups. 

Upon treatment with suitable cobalt complexes, methylbutynol cyclizes to a 1,2,4-substituted benzene. Nickel complexes give the 1,3,5-isomer (196), sometimes accompanied by linear polymer (25) or a mixture of tetrasubstituted cyclooctatetraenes (26). 

Hexachlorocyclotriphosphazene (cycHc trimer) is a respiratory irritant. Nausea has also been noted on exposure (10). Intravenous and intraperitoneal toxicity measurements were made on mice. The highest nonlethal dose (LDq) was measured as 20 mg/kg (11). Linear chloropolymer is also beUeved to be toxic (10). Upon organic substitution, the high molecular weight linear polymers have been shown to be inert. Rat implants of eight different polyphosphazene homopolymers indicated low levels of tissue toxicity (12). EZ has been found to be reasonably compatible with blood (13), and has lower hpid absorption than fiuorosihcone. 

Polymerization of alkynes by Ni" complexes produces a variety of products which depend on conditions and especially on the particular nickel complex used. If, for instance, O-donor ligands such as acetylacetone or salicaldehyde are employed in a solvent such as tetrahydrofuran or dioxan, 4 coordination sites are available and cyclotetramerization occurs to give mainly cyclo-octatetraene (cot). If a less-labile ligand such as PPhj is incorporated, the coordination sites required for tetramerization are not available and cyclic trimerization to benzene predominates (Fig. A). These syntheses are amenable to extensive variation and adaptation. Substituted ring systems can be obtained from the appropriately substituted alkynes while linear polymers can also be produced. 

Addition polymerization is employed primarily with substituted or unsuhstituted olefins and conjugated diolefins. Addition polymerization initiators are free radicals, anions, cations, and coordination compounds. In addition polymerization, a chain grows simply hy adding monomer molecules to a propagating chain. The first step is to add a free radical, a cationic or an anionic initiator (I ) to the monomer. For example, in ethylene polymerization (with a special catalyst), the chain grows hy attaching the ethylene units one after another until the polymer terminates. This type of addition produces a linear polymer ... 

The slightly galactosylated mannans are essentially linear polymers. As a result of their cellulose-like (1 4)-/3-D-mannan backbone, they tend towards self-association, insolubility, and crystallinity. Crystallographic study of C. spectabilis seed GaM [180] with a Man Gal ratio 2.65 1 suggested an orthorhombic unit cell with lattice constants of a = 9.12, b = 25.63, and c = 10.28 the dimension b was shown to be sensitive to the degree of galactose substitution and the hydration conditions [180 and references therein, [191]]. 

Indeed, cumyl carbocations are known to be effective initiators of IB polymerization, while the p-substituted benzyl cation is expected to react effectively with IB (p-methylstyrene and IB form a nearly ideal copolymerization system ). Severe disparity between the reactivities of the vinyl and cumyl ether groups of the inimer would result in either linear polymers or branched polymers with much lower MW than predicted for an in/mcr-mediated living polymerization. Styrene was subsequently blocked from the tert-chloride chain ends of high-MW DIB, activated by excess TiCU (Scheme 7.2). 

For complete rigor the distribution previously presented (Eqs. 1, 2, and 3 and Figs. 51 and 52) for linear polymer chains should be modified through substitution of p for the over-all extent of reaction p. Thus, for example, Eq. (3) for the weight fraction should be replaced with... 

When both the donor and the acceptor modules are bidentate, infinite chain (ID polymers) are formed. The simplest case is when the axes of the donor and acceptor sites are parallel and coaxial so that linear polymers are formed. This is the case in the homopolymers formed by bidentate and self-complementary tectons (e.g. 4-iodopyridine [157], 4-iodobenzonitrile [71, 72], halocyanoacetylenes [70]) and in the co-polymers formed when dihalo-carbons interact with dinitrogen, or dioxygen, substituted hydrocarbons (e.g. the systems formed when 1,4-DITFB, or 1,4-DIB, interact with 4,4/-BPY [50], when 1,4-dinitrobenzene interacts with 1,4-DIB [ 158-162]J, and when 1,4-DITFB interacts with DABCO [163]) (Fig. 7). 

The urge of polymer scientists to develop new materials is driven by society s wish to substitute conventional materials by plastics and thereby gain in performance. One reason for the emerging interest in hyperbranched polymers and other macromolecular architectures is their different properties compared to conventional, linear polymers. 

To obtain linear polymers, the phenolic nucleus must be substituted in the 2-and 6-positions. 

Most general purpose linear polymers, such as polyolefins, PS, PVC, and polymethyl methacrylate (PMMA), are not suitable for use at temperatures above 100 °C. PMMA and other polymers of 1,1-substituted vinyl monomers, such as poly-a-methylstyrene, decompose almost quantitatively to their monomers at elevated temperatures. However, the Tg and Tm values of these polymers are greater than those of polymers from 1-substituted vinyl monomers. For example, the Tg values of polymethyl acrylate (PMA) and PMMA are 276 and 381 K, respectively. 

A similar problem was encountered by the ROMP of a borane substituted cyclooctene with an early transition metal catalyst followed by oxidation to yield an alcohol-functionalized linear polymer (32). 

The molecular architecture of a polyphosphazene has a profound influence on properties. For example, linear and tri-star trifluoroethoxy-substituted polymers with the same molecular weight (1.2 x 104 or higher) have strikingly different properties.138 The linear polymers are white, fibrous materials that readily form films and fibers, whereas the tri-arm star polymers are viscous gums. One is crystalline and the other is amorphous. Cyclolinear polymers are usually soluble and flexible. Cyclomatrix polymers are insoluble and rigid. Linear polymers can be crystalline, but graft or comb polymers are usually amorphous. 

Shimomura, T. Funaki, T. Ito, K. Choi, B.-K. and Hashizume, T. (2002) Circular dichroism study of the inclusion-dissociation behavior of complexes between a molecular nanotube and azobenzene substituted linear polymers, J. Incl. Phenom. 44, 275-278. 

The use of the anions of sulfonamides to prepare linear polymers from several different 1-substituted A-tosyl- and -mesyl-aziridines has been reported.144... 

Substituted allenes undergo polymerisation to linear polymers in the presence of both Ziegler-Natta catalysts, e.g. VOCl3 Al(i-Bu)3 [440], and monometallic complexes such as Ni complexes [442], Amorphous polymers consisting of 1,2-linked monomeric units (predominant) and 2,3-linked monomeric units have been obtained from 1,2-butadiene (H2C=C=CHCH3) ... 

Cross-linked resins of polyamidoamine structure can be prepared in the same way as the linear polymers by partly substituting a, m-diaminoalkanes for the same quantity of difunctional aminic monomers in the polymerization process. According to the general scheme of poly(amido-amine)synthesis, bis(primary amine)s, having four mobile hydrogens, act as tetrafunctional monomers 47). 

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